1 /*
   2  * Copyright (c) 1994, 2010, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package java.lang;
  26 
  27 import java.io.InputStream;
  28 import java.io.IOException;
  29 import java.io.File;
  30 import java.lang.reflect.Constructor;
  31 import java.lang.reflect.InvocationTargetException;
  32 import java.net.MalformedURLException;
  33 import java.net.URL;
  34 import java.security.AccessController;
  35 import java.security.AccessControlContext;
  36 import java.security.CodeSource;
  37 import java.security.Policy;
  38 import java.security.PrivilegedAction;
  39 import java.security.PrivilegedActionException;
  40 import java.security.PrivilegedExceptionAction;
  41 import java.security.ProtectionDomain;
  42 import java.security.cert.Certificate;
  43 import java.util.Collections;
  44 import java.util.Enumeration;
  45 import java.util.HashMap;
  46 import java.util.HashSet;
  47 import java.util.Set;
  48 import java.util.Stack;
  49 import java.util.Map;
  50 import java.util.Vector;
  51 import java.util.Hashtable;
  52 import java.util.WeakHashMap;
  53 import java.util.concurrent.ConcurrentHashMap;

  54 import sun.misc.ClassFileTransformer;
  55 import sun.misc.CompoundEnumeration;
  56 import sun.misc.Resource;
  57 import sun.misc.URLClassPath;
  58 import sun.misc.VM;
  59 import sun.reflect.Reflection;
  60 import sun.security.util.SecurityConstants;
  61 
  62 /**
  63  * A class loader is an object that is responsible for loading classes. The
  64  * class <tt>ClassLoader</tt> is an abstract class.  Given the <a
  65  * href="#name">binary name</a> of a class, a class loader should attempt to
  66  * locate or generate data that constitutes a definition for the class.  A
  67  * typical strategy is to transform the name into a file name and then read a
  68  * "class file" of that name from a file system.
  69  *
  70  * <p> Every {@link Class <tt>Class</tt>} object contains a {@link
  71  * Class#getClassLoader() reference} to the <tt>ClassLoader</tt> that defined
  72  * it.
  73  *
  74  * <p> <tt>Class</tt> objects for array classes are not created by class
  75  * loaders, but are created automatically as required by the Java runtime.
  76  * The class loader for an array class, as returned by {@link
  77  * Class#getClassLoader()} is the same as the class loader for its element
  78  * type; if the element type is a primitive type, then the array class has no
  79  * class loader.
  80  *
  81  * <p> Applications implement subclasses of <tt>ClassLoader</tt> in order to
  82  * extend the manner in which the Java virtual machine dynamically loads
  83  * classes.
  84  *
  85  * <p> Class loaders may typically be used by security managers to indicate
  86  * security domains.
  87  *
  88  * <p> The <tt>ClassLoader</tt> class uses a delegation model to search for
  89  * classes and resources.  Each instance of <tt>ClassLoader</tt> has an
  90  * associated parent class loader.  When requested to find a class or
  91  * resource, a <tt>ClassLoader</tt> instance will delegate the search for the
  92  * class or resource to its parent class loader before attempting to find the
  93  * class or resource itself.  The virtual machine's built-in class loader,
  94  * called the "bootstrap class loader", does not itself have a parent but may
  95  * serve as the parent of a <tt>ClassLoader</tt> instance.
  96  *
  97  * <p> Class loaders that support concurrent loading of classes are known as
  98  * <em>parallel capable</em> class loaders and are required to register
  99  * themselves at their class initialization time by invoking the
 100  * {@link
 101  * #registerAsParallelCapable <tt>ClassLoader.registerAsParallelCapable</tt>}
 102  * method. Note that the <tt>ClassLoader</tt> class is registered as parallel
 103  * capable by default. However, its subclasses still need to register themselves
 104  * if they are parallel capable. <br>
 105  * In environments in which the delegation model is not strictly
 106  * hierarchical, class loaders need to be parallel capable, otherwise class
 107  * loading can lead to deadlocks because the loader lock is held for the
 108  * duration of the class loading process (see {@link #loadClass
 109  * <tt>loadClass</tt>} methods).
 110  *
 111  * <p> Normally, the Java virtual machine loads classes from the local file
 112  * system in a platform-dependent manner.  For example, on UNIX systems, the
 113  * virtual machine loads classes from the directory defined by the
 114  * <tt>CLASSPATH</tt> environment variable.
 115  *
 116  * <p> However, some classes may not originate from a file; they may originate
 117  * from other sources, such as the network, or they could be constructed by an
 118  * application.  The method {@link #defineClass(String, byte[], int, int)
 119  * <tt>defineClass</tt>} converts an array of bytes into an instance of class
 120  * <tt>Class</tt>. Instances of this newly defined class can be created using
 121  * {@link Class#newInstance <tt>Class.newInstance</tt>}.
 122  *
 123  * <p> The methods and constructors of objects created by a class loader may
 124  * reference other classes.  To determine the class(es) referred to, the Java
 125  * virtual machine invokes the {@link #loadClass <tt>loadClass</tt>} method of
 126  * the class loader that originally created the class.
 127  *
 128  * <p> For example, an application could create a network class loader to
 129  * download class files from a server.  Sample code might look like:
 130  *
 131  * <blockquote><pre>
 132  *   ClassLoader loader&nbsp;= new NetworkClassLoader(host,&nbsp;port);
 133  *   Object main&nbsp;= loader.loadClass("Main", true).newInstance();
 134  *       &nbsp;.&nbsp;.&nbsp;.
 135  * </pre></blockquote>
 136  *
 137  * <p> The network class loader subclass must define the methods {@link
 138  * #findClass <tt>findClass</tt>} and <tt>loadClassData</tt> to load a class
 139  * from the network.  Once it has downloaded the bytes that make up the class,
 140  * it should use the method {@link #defineClass <tt>defineClass</tt>} to
 141  * create a class instance.  A sample implementation is:
 142  *
 143  * <blockquote><pre>
 144  *     class NetworkClassLoader extends ClassLoader {
 145  *         String host;
 146  *         int port;
 147  *
 148  *         public Class findClass(String name) {
 149  *             byte[] b = loadClassData(name);
 150  *             return defineClass(name, b, 0, b.length);
 151  *         }
 152  *
 153  *         private byte[] loadClassData(String name) {
 154  *             // load the class data from the connection
 155  *             &nbsp;.&nbsp;.&nbsp;.
 156  *         }
 157  *     }
 158  * </pre></blockquote>
 159  *
 160  * <h4> <a name="name">Binary names</a> </h4>
 161  *
 162  * <p> Any class name provided as a {@link String} parameter to methods in
 163  * <tt>ClassLoader</tt> must be a binary name as defined by the <a
 164  * href="http://java.sun.com/docs/books/jls/">Java Language Specification</a>.
 165  *
 166  * <p> Examples of valid class names include:
 167  * <blockquote><pre>
 168  *   "java.lang.String"
 169  *   "javax.swing.JSpinner$DefaultEditor"
 170  *   "java.security.KeyStore$Builder$FileBuilder$1"
 171  *   "java.net.URLClassLoader$3$1"
 172  * </pre></blockquote>
 173  *
 174  * @see      #resolveClass(Class)
 175  * @since 1.0
 176  */
 177 public abstract class ClassLoader {
 178 
 179     private static native void registerNatives();
 180     static {
 181         registerNatives();
 182     }
 183 
 184     // The parent class loader for delegation
 185     // Note: VM hardcoded the offset of this field, thus all new fields
 186     // must be added *after* it.
 187     private final ClassLoader parent;
 188 
 189     /**
 190      * Encapsulates the set of parallel capable loader types.
 191      */
 192     private static class ParallelLoaders {
 193         private ParallelLoaders() {}
 194 
 195         // the set of parallel capable loader types
 196         private static final Set<Class<? extends ClassLoader>> loaderTypes =
 197             Collections.newSetFromMap(
 198                 new WeakHashMap<Class<? extends ClassLoader>, Boolean>());
 199         static {
 200             synchronized (loaderTypes) { loaderTypes.add(ClassLoader.class); }
 201         }
 202 
 203         /**
 204          * Registers the given class loader type as parallel capabale.
 205          * Returns {@code true} is successfully registered; {@code false} if
 206          * loader's super class is not registered.
 207          */
 208         static boolean register(Class<? extends ClassLoader> c) {
 209             synchronized (loaderTypes) {
 210                 if (loaderTypes.contains(c.getSuperclass())) {
 211                     // register the class loader as parallel capable
 212                     // if and only if all of its super classes are.
 213                     // Note: given current classloading sequence, if
 214                     // the immediate super class is parallel capable,
 215                     // all the super classes higher up must be too.
 216                     loaderTypes.add(c);
 217                     return true;
 218                 } else {
 219                     return false;
 220                 }
 221             }
 222         }
 223 
 224         /**
 225          * Returns {@code true} if the given class loader type is
 226          * registered as parallel capable.
 227          */
 228         static boolean isRegistered(Class<? extends ClassLoader> c) {
 229             synchronized (loaderTypes) {
 230                 return loaderTypes.contains(c);
 231             }
 232         }
 233     }
 234 
 235     // Maps class name to the corresponding lock object when the current
 236     // class loader is parallel capable.
 237     // Note: VM also uses this field to decide if the current class loader
 238     // is parallel capable and the appropriate lock object for class loading.
 239     private final ConcurrentHashMap<String, Object> parallelLockMap;
 240 
 241     // Hashtable that maps packages to certs
 242     private final Map <String, Certificate[]> package2certs;
 243 
 244     // Shared among all packages with unsigned classes
 245     private static final Certificate[] nocerts = new Certificate[0];
 246 
 247     // The classes loaded by this class loader. The only purpose of this table
 248     // is to keep the classes from being GC'ed until the loader is GC'ed.
 249     private final Vector<Class<?>> classes = new Vector<>();
 250 
 251     // The "default" domain. Set as the default ProtectionDomain on newly
 252     // created classes.
 253     private final ProtectionDomain defaultDomain =
 254         new ProtectionDomain(new CodeSource(null, (Certificate[]) null),
 255                              null, this, null);
 256 
 257     // The initiating protection domains for all classes loaded by this loader
 258     private final Set<ProtectionDomain> domains;
 259 
 260     // Invoked by the VM to record every loaded class with this loader.
 261     void addClass(Class c) {
 262         classes.addElement(c);
 263     }
 264 
 265     // The packages defined in this class loader.  Each package name is mapped
 266     // to its corresponding Package object.
 267     // @GuardedBy("itself")
 268     private final HashMap<String, Package> packages = new HashMap<>();
 269 
 270     private static Void checkCreateClassLoader() {
 271         SecurityManager security = System.getSecurityManager();
 272         if (security != null) {
 273             security.checkCreateClassLoader();
 274         }
 275         return null;
 276     }
 277 
 278     private ClassLoader(Void unused, ClassLoader parent) {
 279         this.parent = parent;
 280         if (ParallelLoaders.isRegistered(this.getClass())) {
 281             parallelLockMap = new ConcurrentHashMap<>();
 282             package2certs = new ConcurrentHashMap<>();
 283             domains =
 284                 Collections.synchronizedSet(new HashSet<ProtectionDomain>());
 285             assertionLock = new Object();
 286         } else {
 287             // no finer-grained lock; lock on the classloader instance
 288             parallelLockMap = null;
 289             package2certs = new Hashtable<>();
 290             domains = new HashSet<>();
 291             assertionLock = this;
 292         }
 293     }
 294 
 295     /**
 296      * Creates a new class loader using the specified parent class loader for
 297      * delegation.
 298      *
 299      * <p> If there is a security manager, its {@link
 300      * SecurityManager#checkCreateClassLoader()
 301      * <tt>checkCreateClassLoader</tt>} method is invoked.  This may result in
 302      * a security exception.  </p>
 303      *
 304      * @param  parent
 305      *         The parent class loader
 306      *
 307      * @throws  SecurityException
 308      *          If a security manager exists and its
 309      *          <tt>checkCreateClassLoader</tt> method doesn't allow creation
 310      *          of a new class loader.
 311      *
 312      * @since  1.2
 313      */
 314     protected ClassLoader(ClassLoader parent) {
 315         this(checkCreateClassLoader(), parent);
 316     }
 317 
 318     /**
 319      * Creates a new class loader using the <tt>ClassLoader</tt> returned by
 320      * the method {@link #getSystemClassLoader()
 321      * <tt>getSystemClassLoader()</tt>} as the parent class loader.
 322      *
 323      * <p> If there is a security manager, its {@link
 324      * SecurityManager#checkCreateClassLoader()
 325      * <tt>checkCreateClassLoader</tt>} method is invoked.  This may result in
 326      * a security exception.  </p>
 327      *
 328      * @throws  SecurityException
 329      *          If a security manager exists and its
 330      *          <tt>checkCreateClassLoader</tt> method doesn't allow creation
 331      *          of a new class loader.
 332      */
 333     protected ClassLoader() {
 334         this(checkCreateClassLoader(), getSystemClassLoader());
 335     }
 336 
 337     // -- Class --
 338 
 339     /**
 340      * Loads the class with the specified <a href="#name">binary name</a>.
 341      * This method searches for classes in the same manner as the {@link
 342      * #loadClass(String, boolean)} method.  It is invoked by the Java virtual
 343      * machine to resolve class references.  Invoking this method is equivalent
 344      * to invoking {@link #loadClass(String, boolean) <tt>loadClass(name,
 345      * false)</tt>}.  </p>
 346      *
 347      * @param  name
 348      *         The <a href="#name">binary name</a> of the class
 349      *
 350      * @return  The resulting <tt>Class</tt> object
 351      *
 352      * @throws  ClassNotFoundException
 353      *          If the class was not found
 354      */
 355     public Class<?> loadClass(String name) throws ClassNotFoundException {
 356         return loadClass(name, false);
 357     }
 358 
 359     /**
 360      * Loads the class with the specified <a href="#name">binary name</a>.  The
 361      * default implementation of this method searches for classes in the
 362      * following order:
 363      *
 364      * <p><ol>
 365      *
 366      *   <li><p> Invoke {@link #findLoadedClass(String)} to check if the class
 367      *   has already been loaded.  </p></li>
 368      *
 369      *   <li><p> Invoke the {@link #loadClass(String) <tt>loadClass</tt>} method
 370      *   on the parent class loader.  If the parent is <tt>null</tt> the class
 371      *   loader built-in to the virtual machine is used, instead.  </p></li>
 372      *
 373      *   <li><p> Invoke the {@link #findClass(String)} method to find the
 374      *   class.  </p></li>
 375      *
 376      * </ol>
 377      *
 378      * <p> If the class was found using the above steps, and the
 379      * <tt>resolve</tt> flag is true, this method will then invoke the {@link
 380      * #resolveClass(Class)} method on the resulting <tt>Class</tt> object.
 381      *
 382      * <p> Subclasses of <tt>ClassLoader</tt> are encouraged to override {@link
 383      * #findClass(String)}, rather than this method.  </p>
 384      *
 385      * <p> Unless overridden, this method synchronizes on the result of
 386      * {@link #getClassLoadingLock <tt>getClassLoadingLock</tt>} method
 387      * during the entire class loading process.
 388      *
 389      * @param  name
 390      *         The <a href="#name">binary name</a> of the class
 391      *
 392      * @param  resolve
 393      *         If <tt>true</tt> then resolve the class
 394      *
 395      * @return  The resulting <tt>Class</tt> object
 396      *
 397      * @throws  ClassNotFoundException
 398      *          If the class could not be found
 399      */
 400     protected Class<?> loadClass(String name, boolean resolve)
 401         throws ClassNotFoundException
 402     {
 403         synchronized (getClassLoadingLock(name)) {
 404             // First, check if the class has already been loaded
 405             Class c = findLoadedClass(name);
 406             if (c == null) {
 407                 long t0 = System.nanoTime();
 408                 try {
 409                     if (parent != null) {
 410                         c = parent.loadClass(name, false);
 411                     } else {
 412                         c = findBootstrapClassOrNull(name);
 413                     }
 414                 } catch (ClassNotFoundException e) {
 415                     // ClassNotFoundException thrown if class not found
 416                     // from the non-null parent class loader
 417                 }
 418 
 419                 if (c == null) {
 420                     // If still not found, then invoke findClass in order
 421                     // to find the class.
 422                     long t1 = System.nanoTime();
 423                     c = findClass(name);
 424 
 425                     // this is the defining class loader; record the stats
 426                     sun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0);
 427                     sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);
 428                     sun.misc.PerfCounter.getFindClasses().increment();
 429                 }
 430             }
 431             if (resolve) {
 432                 resolveClass(c);
 433             }
 434             return c;
 435         }
 436     }
 437 
 438     /**
 439      * Returns the lock object for class loading operations.
 440      * For backward compatibility, the default implementation of this method
 441      * behaves as follows. If this ClassLoader object is registered as
 442      * parallel capable, the method returns a dedicated object associated
 443      * with the specified class name. Otherwise, the method returns this
 444      * ClassLoader object. </p>
 445      *
 446      * @param  className
 447      *         The name of the to-be-loaded class
 448      *
 449      * @return the lock for class loading operations
 450      *
 451      * @throws NullPointerException
 452      *         If registered as parallel capable and <tt>className</tt> is null
 453      *
 454      * @see #loadClass(String, boolean)
 455      *
 456      * @since  1.7
 457      */
 458     protected Object getClassLoadingLock(String className) {
 459         Object lock = this;
 460         if (parallelLockMap != null) {
 461             Object newLock = new Object();
 462             lock = parallelLockMap.putIfAbsent(className, newLock);
 463             if (lock == null) {
 464                 lock = newLock;
 465             }
 466         }
 467         return lock;
 468     }
 469 
 470     // This method is invoked by the virtual machine to load a class.
 471     private Class loadClassInternal(String name)
 472         throws ClassNotFoundException
 473     {
 474         // For backward compatibility, explicitly lock on 'this' when
 475         // the current class loader is not parallel capable.
 476         if (parallelLockMap == null) {
 477             synchronized (this) {
 478                  return loadClass(name);
 479             }
 480         } else {
 481             return loadClass(name);
 482         }
 483     }
 484 
 485     // Invoked by the VM after loading class with this loader.
 486     private void checkPackageAccess(Class cls, ProtectionDomain pd) {
 487         final SecurityManager sm = System.getSecurityManager();
 488         if (sm != null) {
 489             final String name = cls.getName();
 490             final int i = name.lastIndexOf('.');
 491             if (i != -1) {
 492                 AccessController.doPrivileged(new PrivilegedAction<Void>() {
 493                     public Void run() {
 494                         sm.checkPackageAccess(name.substring(0, i));
 495                         return null;
 496                     }
 497                 }, new AccessControlContext(new ProtectionDomain[] {pd}));
 498             }
 499         }
 500         domains.add(pd);
 501     }
 502 
 503     /**
 504      * Finds the class with the specified <a href="#name">binary name</a>.
 505      * This method should be overridden by class loader implementations that
 506      * follow the delegation model for loading classes, and will be invoked by
 507      * the {@link #loadClass <tt>loadClass</tt>} method after checking the
 508      * parent class loader for the requested class.  The default implementation
 509      * throws a <tt>ClassNotFoundException</tt>.  </p>
 510      *
 511      * @param  name
 512      *         The <a href="#name">binary name</a> of the class
 513      *
 514      * @return  The resulting <tt>Class</tt> object
 515      *
 516      * @throws  ClassNotFoundException
 517      *          If the class could not be found
 518      *
 519      * @since  1.2
 520      */
 521     protected Class<?> findClass(String name) throws ClassNotFoundException {
 522         throw new ClassNotFoundException(name);
 523     }
 524 
 525     /**
 526      * Converts an array of bytes into an instance of class <tt>Class</tt>.
 527      * Before the <tt>Class</tt> can be used it must be resolved.  This method
 528      * is deprecated in favor of the version that takes a <a
 529      * href="#name">binary name</a> as its first argument, and is more secure.
 530      *
 531      * @param  b
 532      *         The bytes that make up the class data.  The bytes in positions
 533      *         <tt>off</tt> through <tt>off+len-1</tt> should have the format
 534      *         of a valid class file as defined by the <a
 535      *         href="http://java.sun.com/docs/books/vmspec/">Java Virtual
 536      *         Machine Specification</a>.
 537      *
 538      * @param  off
 539      *         The start offset in <tt>b</tt> of the class data
 540      *
 541      * @param  len
 542      *         The length of the class data
 543      *
 544      * @return  The <tt>Class</tt> object that was created from the specified
 545      *          class data
 546      *
 547      * @throws  ClassFormatError
 548      *          If the data did not contain a valid class
 549      *
 550      * @throws  IndexOutOfBoundsException
 551      *          If either <tt>off</tt> or <tt>len</tt> is negative, or if
 552      *          <tt>off+len</tt> is greater than <tt>b.length</tt>.
 553      *
 554      * @throws  SecurityException
 555      *          If an attempt is made to add this class to a package that
 556      *          contains classes that were signed by a different set of
 557      *          certificates than this class, or if an attempt is made
 558      *          to define a class in a package with a fully-qualified name
 559      *          that starts with "{@code java.}".
 560      *
 561      * @see  #loadClass(String, boolean)
 562      * @see  #resolveClass(Class)
 563      *
 564      * @deprecated  Replaced by {@link #defineClass(String, byte[], int, int)
 565      * defineClass(String, byte[], int, int)}
 566      */
 567     @Deprecated
 568     protected final Class<?> defineClass(byte[] b, int off, int len)
 569         throws ClassFormatError
 570     {
 571         return defineClass(null, b, off, len, null);
 572     }
 573 
 574     /**
 575      * Converts an array of bytes into an instance of class <tt>Class</tt>.
 576      * Before the <tt>Class</tt> can be used it must be resolved.
 577      *
 578      * <p> This method assigns a default {@link java.security.ProtectionDomain
 579      * <tt>ProtectionDomain</tt>} to the newly defined class.  The
 580      * <tt>ProtectionDomain</tt> is effectively granted the same set of
 581      * permissions returned when {@link
 582      * java.security.Policy#getPermissions(java.security.CodeSource)
 583      * <tt>Policy.getPolicy().getPermissions(new CodeSource(null, null))</tt>}
 584      * is invoked.  The default domain is created on the first invocation of
 585      * {@link #defineClass(String, byte[], int, int) <tt>defineClass</tt>},
 586      * and re-used on subsequent invocations.
 587      *
 588      * <p> To assign a specific <tt>ProtectionDomain</tt> to the class, use
 589      * the {@link #defineClass(String, byte[], int, int,
 590      * java.security.ProtectionDomain) <tt>defineClass</tt>} method that takes a
 591      * <tt>ProtectionDomain</tt> as one of its arguments.  </p>
 592      *
 593      * @param  name
 594      *         The expected <a href="#name">binary name</a> of the class, or
 595      *         <tt>null</tt> if not known
 596      *
 597      * @param  b
 598      *         The bytes that make up the class data.  The bytes in positions
 599      *         <tt>off</tt> through <tt>off+len-1</tt> should have the format
 600      *         of a valid class file as defined by the <a
 601      *         href="http://java.sun.com/docs/books/vmspec/">Java Virtual
 602      *         Machine Specification</a>.
 603      *
 604      * @param  off
 605      *         The start offset in <tt>b</tt> of the class data
 606      *
 607      * @param  len
 608      *         The length of the class data
 609      *
 610      * @return  The <tt>Class</tt> object that was created from the specified
 611      *          class data.
 612      *
 613      * @throws  ClassFormatError
 614      *          If the data did not contain a valid class
 615      *
 616      * @throws  IndexOutOfBoundsException
 617      *          If either <tt>off</tt> or <tt>len</tt> is negative, or if
 618      *          <tt>off+len</tt> is greater than <tt>b.length</tt>.
 619      *
 620      * @throws  SecurityException
 621      *          If an attempt is made to add this class to a package that
 622      *          contains classes that were signed by a different set of
 623      *          certificates than this class (which is unsigned), or if
 624      *          <tt>name</tt> begins with "<tt>java.</tt>".
 625      *
 626      * @see  #loadClass(String, boolean)
 627      * @see  #resolveClass(Class)
 628      * @see  java.security.CodeSource
 629      * @see  java.security.SecureClassLoader
 630      *
 631      * @since  1.1
 632      */
 633     protected final Class<?> defineClass(String name, byte[] b, int off, int len)
 634         throws ClassFormatError
 635     {
 636         return defineClass(name, b, off, len, null);
 637     }
 638 
 639     /* Determine protection domain, and check that:
 640         - not define java.* class,
 641         - signer of this class matches signers for the rest of the classes in
 642           package.
 643     */
 644     private ProtectionDomain preDefineClass(String name,
 645                                             ProtectionDomain pd)
 646     {
 647         if (!checkName(name))
 648             throw new NoClassDefFoundError("IllegalName: " + name);
 649 
 650         if ((name != null) && name.startsWith("java.")) {
 651             throw new SecurityException
 652                 ("Prohibited package name: " +
 653                  name.substring(0, name.lastIndexOf('.')));
 654         }
 655         if (pd == null) {
 656             pd = defaultDomain;
 657         }
 658 
 659         if (name != null) checkCerts(name, pd.getCodeSource());
 660 
 661         return pd;
 662     }
 663 
 664     private String defineClassSourceLocation(ProtectionDomain pd)
 665     {
 666         CodeSource cs = pd.getCodeSource();
 667         String source = null;
 668         if (cs != null && cs.getLocation() != null) {
 669             source = cs.getLocation().toString();
 670         }
 671         return source;
 672     }
 673 
 674     private Class defineTransformedClass(String name, byte[] b, int off, int len,
 675                                          ProtectionDomain pd,
 676                                          ClassFormatError cfe, String source)
 677       throws ClassFormatError
 678     {
 679         // Class format error - try to transform the bytecode and
 680         // define the class again
 681         //
 682         ClassFileTransformer[] transformers =
 683             ClassFileTransformer.getTransformers();
 684         Class c = null;
 685 
 686         if (transformers != null) {
 687             for (ClassFileTransformer transformer : transformers) {
 688                 try {
 689                     // Transform byte code using transformer
 690                     byte[] tb = transformer.transform(b, off, len);
 691                     c = defineClass1(name, tb, 0, tb.length,
 692                                      pd, source);
 693                     break;
 694                 } catch (ClassFormatError cfe2)     {
 695                     // If ClassFormatError occurs, try next transformer
 696                 }
 697             }
 698         }
 699 
 700         // Rethrow original ClassFormatError if unable to transform
 701         // bytecode to well-formed
 702         //
 703         if (c == null)
 704             throw cfe;
 705 
 706         return c;
 707     }
 708 
 709     private void postDefineClass(Class c, ProtectionDomain pd)
 710     {
 711         if (pd.getCodeSource() != null) {
 712             Certificate certs[] = pd.getCodeSource().getCertificates();
 713             if (certs != null)
 714                 setSigners(c, certs);
 715         }
 716     }
 717 
 718     /**
 719      * Converts an array of bytes into an instance of class <tt>Class</tt>,
 720      * with an optional <tt>ProtectionDomain</tt>.  If the domain is
 721      * <tt>null</tt>, then a default domain will be assigned to the class as
 722      * specified in the documentation for {@link #defineClass(String, byte[],
 723      * int, int)}.  Before the class can be used it must be resolved.
 724      *
 725      * <p> The first class defined in a package determines the exact set of
 726      * certificates that all subsequent classes defined in that package must
 727      * contain.  The set of certificates for a class is obtained from the
 728      * {@link java.security.CodeSource <tt>CodeSource</tt>} within the
 729      * <tt>ProtectionDomain</tt> of the class.  Any classes added to that
 730      * package must contain the same set of certificates or a
 731      * <tt>SecurityException</tt> will be thrown.  Note that if
 732      * <tt>name</tt> is <tt>null</tt>, this check is not performed.
 733      * You should always pass in the <a href="#name">binary name</a> of the
 734      * class you are defining as well as the bytes.  This ensures that the
 735      * class you are defining is indeed the class you think it is.
 736      *
 737      * <p> The specified <tt>name</tt> cannot begin with "<tt>java.</tt>", since
 738      * all classes in the "<tt>java.*</tt> packages can only be defined by the
 739      * bootstrap class loader.  If <tt>name</tt> is not <tt>null</tt>, it
 740      * must be equal to the <a href="#name">binary name</a> of the class
 741      * specified by the byte array "<tt>b</tt>", otherwise a {@link
 742      * <tt>NoClassDefFoundError</tt>} will be thrown.  </p>
 743      *
 744      * @param  name
 745      *         The expected <a href="#name">binary name</a> of the class, or
 746      *         <tt>null</tt> if not known
 747      *
 748      * @param  b
 749      *         The bytes that make up the class data. The bytes in positions
 750      *         <tt>off</tt> through <tt>off+len-1</tt> should have the format
 751      *         of a valid class file as defined by the <a
 752      *         href="http://java.sun.com/docs/books/vmspec/">Java Virtual
 753      *         Machine Specification</a>.
 754      *
 755      * @param  off
 756      *         The start offset in <tt>b</tt> of the class data
 757      *
 758      * @param  len
 759      *         The length of the class data
 760      *
 761      * @param  protectionDomain
 762      *         The ProtectionDomain of the class
 763      *
 764      * @return  The <tt>Class</tt> object created from the data,
 765      *          and optional <tt>ProtectionDomain</tt>.
 766      *
 767      * @throws  ClassFormatError
 768      *          If the data did not contain a valid class
 769      *
 770      * @throws  NoClassDefFoundError
 771      *          If <tt>name</tt> is not equal to the <a href="#name">binary
 772      *          name</a> of the class specified by <tt>b</tt>
 773      *
 774      * @throws  IndexOutOfBoundsException
 775      *          If either <tt>off</tt> or <tt>len</tt> is negative, or if
 776      *          <tt>off+len</tt> is greater than <tt>b.length</tt>.
 777      *
 778      * @throws  SecurityException
 779      *          If an attempt is made to add this class to a package that
 780      *          contains classes that were signed by a different set of
 781      *          certificates than this class, or if <tt>name</tt> begins with
 782      *          "<tt>java.</tt>".
 783      */
 784     protected final Class<?> defineClass(String name, byte[] b, int off, int len,
 785                                          ProtectionDomain protectionDomain)
 786         throws ClassFormatError
 787     {
 788         protectionDomain = preDefineClass(name, protectionDomain);
 789 
 790         Class c = null;
 791         String source = defineClassSourceLocation(protectionDomain);
 792 
 793         try {
 794             c = defineClass1(name, b, off, len, protectionDomain, source);
 795         } catch (ClassFormatError cfe) {
 796             c = defineTransformedClass(name, b, off, len, protectionDomain, cfe,
 797                                        source);
 798         }
 799 
 800         postDefineClass(c, protectionDomain);
 801         return c;
 802     }
 803 
 804     /**
 805      * Converts a {@link java.nio.ByteBuffer <tt>ByteBuffer</tt>}
 806      * into an instance of class <tt>Class</tt>,
 807      * with an optional <tt>ProtectionDomain</tt>.  If the domain is
 808      * <tt>null</tt>, then a default domain will be assigned to the class as
 809      * specified in the documentation for {@link #defineClass(String, byte[],
 810      * int, int)}.  Before the class can be used it must be resolved.
 811      *
 812      * <p>The rules about the first class defined in a package determining the
 813      * set of certificates for the package, and the restrictions on class names
 814      * are identical to those specified in the documentation for {@link
 815      * #defineClass(String, byte[], int, int, ProtectionDomain)}.
 816      *
 817      * <p> An invocation of this method of the form
 818      * <i>cl</i><tt>.defineClass(</tt><i>name</i><tt>,</tt>
 819      * <i>bBuffer</i><tt>,</tt> <i>pd</i><tt>)</tt> yields exactly the same
 820      * result as the statements
 821      *
 822      * <blockquote><tt>
 823      * ...<br>
 824      * byte[] temp = new byte[</tt><i>bBuffer</i><tt>.{@link
 825      * java.nio.ByteBuffer#remaining remaining}()];<br>
 826      *     </tt><i>bBuffer</i><tt>.{@link java.nio.ByteBuffer#get(byte[])
 827      * get}(temp);<br>
 828      *     return {@link #defineClass(String, byte[], int, int, ProtectionDomain)
 829      * </tt><i>cl</i><tt>.defineClass}(</tt><i>name</i><tt>, temp, 0,
 830      * temp.length, </tt><i>pd</i><tt>);<br>
 831      * </tt></blockquote>
 832      *
 833      * @param  name
 834      *         The expected <a href="#name">binary name</a>. of the class, or
 835      *         <tt>null</tt> if not known
 836      *
 837      * @param  b
 838      *         The bytes that make up the class data. The bytes from positions
 839      *         <tt>b.position()</tt> through <tt>b.position() + b.limit() -1
 840      *         </tt> should have the format of a valid class file as defined by
 841      *         the <a href="http://java.sun.com/docs/books/vmspec/">Java Virtual
 842      *         Machine Specification</a>.
 843      *
 844      * @param  protectionDomain
 845      *         The ProtectionDomain of the class, or <tt>null</tt>.
 846      *
 847      * @return  The <tt>Class</tt> object created from the data,
 848      *          and optional <tt>ProtectionDomain</tt>.
 849      *
 850      * @throws  ClassFormatError
 851      *          If the data did not contain a valid class.
 852      *
 853      * @throws  NoClassDefFoundError
 854      *          If <tt>name</tt> is not equal to the <a href="#name">binary
 855      *          name</a> of the class specified by <tt>b</tt>
 856      *
 857      * @throws  SecurityException
 858      *          If an attempt is made to add this class to a package that
 859      *          contains classes that were signed by a different set of
 860      *          certificates than this class, or if <tt>name</tt> begins with
 861      *          "<tt>java.</tt>".
 862      *
 863      * @see      #defineClass(String, byte[], int, int, ProtectionDomain)
 864      *
 865      * @since  1.5
 866      */
 867     protected final Class<?> defineClass(String name, java.nio.ByteBuffer b,
 868                                          ProtectionDomain protectionDomain)
 869         throws ClassFormatError
 870     {
 871         int len = b.remaining();
 872 
 873         // Use byte[] if not a direct ByteBufer:
 874         if (!b.isDirect()) {
 875             if (b.hasArray()) {
 876                 return defineClass(name, b.array(),
 877                                    b.position() + b.arrayOffset(), len,
 878                                    protectionDomain);
 879             } else {
 880                 // no array, or read-only array
 881                 byte[] tb = new byte[len];
 882                 b.get(tb);  // get bytes out of byte buffer.
 883                 return defineClass(name, tb, 0, len, protectionDomain);
 884             }
 885         }
 886 
 887         protectionDomain = preDefineClass(name, protectionDomain);
 888 
 889         Class c = null;
 890         String source = defineClassSourceLocation(protectionDomain);
 891 
 892         try {
 893             c = defineClass2(name, b, b.position(), len, protectionDomain,
 894                              source);
 895         } catch (ClassFormatError cfe) {
 896             byte[] tb = new byte[len];
 897             b.get(tb);  // get bytes out of byte buffer.
 898             c = defineTransformedClass(name, tb, 0, len, protectionDomain, cfe,
 899                                        source);
 900         }
 901 
 902         postDefineClass(c, protectionDomain);
 903         return c;
 904     }
 905 
 906     private native Class defineClass0(String name, byte[] b, int off, int len,
 907                                       ProtectionDomain pd);
 908 
 909     private native Class defineClass1(String name, byte[] b, int off, int len,
 910                                       ProtectionDomain pd, String source);
 911 
 912     private native Class defineClass2(String name, java.nio.ByteBuffer b,
 913                                       int off, int len, ProtectionDomain pd,
 914                                       String source);
 915 
 916     // true if the name is null or has the potential to be a valid binary name
 917     private boolean checkName(String name) {
 918         if ((name == null) || (name.length() == 0))
 919             return true;
 920         if ((name.indexOf('/') != -1)
 921             || (!VM.allowArraySyntax() && (name.charAt(0) == '[')))
 922             return false;
 923         return true;
 924     }
 925 
 926     private void checkCerts(String name, CodeSource cs) {
 927         int i = name.lastIndexOf('.');
 928         String pname = (i == -1) ? "" : name.substring(0, i);
 929 
 930         Certificate[] certs = null;
 931         if (cs != null) {
 932             certs = cs.getCertificates();
 933         }
 934         Certificate[] pcerts = null;
 935         if (parallelLockMap == null) {
 936             synchronized (this) {
 937                 pcerts = package2certs.get(pname);
 938                 if (pcerts == null) {
 939                     package2certs.put(pname, (certs == null? nocerts:certs));
 940                 }
 941             }
 942         } else {
 943             pcerts = ((ConcurrentHashMap<String, Certificate[]>)package2certs).
 944                 putIfAbsent(pname, (certs == null? nocerts:certs));
 945         }
 946         if (pcerts != null && !compareCerts(pcerts, certs)) {
 947             throw new SecurityException("class \""+ name +
 948                  "\"'s signer information does not match signer information of other classes in the same package");
 949         }
 950     }
 951 
 952     /**
 953      * check to make sure the certs for the new class (certs) are the same as
 954      * the certs for the first class inserted in the package (pcerts)
 955      */
 956     private boolean compareCerts(Certificate[] pcerts,
 957                                  Certificate[] certs)
 958     {
 959         // certs can be null, indicating no certs.
 960         if ((certs == null) || (certs.length == 0)) {
 961             return pcerts.length == 0;
 962         }
 963 
 964         // the length must be the same at this point
 965         if (certs.length != pcerts.length)
 966             return false;
 967 
 968         // go through and make sure all the certs in one array
 969         // are in the other and vice-versa.
 970         boolean match;
 971         for (int i = 0; i < certs.length; i++) {
 972             match = false;
 973             for (int j = 0; j < pcerts.length; j++) {
 974                 if (certs[i].equals(pcerts[j])) {
 975                     match = true;
 976                     break;
 977                 }
 978             }
 979             if (!match) return false;
 980         }
 981 
 982         // now do the same for pcerts
 983         for (int i = 0; i < pcerts.length; i++) {
 984             match = false;
 985             for (int j = 0; j < certs.length; j++) {
 986                 if (pcerts[i].equals(certs[j])) {
 987                     match = true;
 988                     break;
 989                 }
 990             }
 991             if (!match) return false;
 992         }
 993 
 994         return true;
 995     }
 996 
 997     /**
 998      * Links the specified class.  This (misleadingly named) method may be
 999      * used by a class loader to link a class.  If the class <tt>c</tt> has
1000      * already been linked, then this method simply returns. Otherwise, the
1001      * class is linked as described in the "Execution" chapter of the <a
1002      * href="http://java.sun.com/docs/books/jls/">Java Language
1003      * Specification</a>.
1004      * </p>
1005      *
1006      * @param  c
1007      *         The class to link
1008      *
1009      * @throws  NullPointerException
1010      *          If <tt>c</tt> is <tt>null</tt>.
1011      *
1012      * @see  #defineClass(String, byte[], int, int)
1013      */
1014     protected final void resolveClass(Class<?> c) {
1015         resolveClass0(c);
1016     }
1017 
1018     private native void resolveClass0(Class c);
1019 
1020     /**
1021      * Finds a class with the specified <a href="#name">binary name</a>,
1022      * loading it if necessary.
1023      *
1024      * <p> This method loads the class through the system class loader (see
1025      * {@link #getSystemClassLoader()}).  The <tt>Class</tt> object returned
1026      * might have more than one <tt>ClassLoader</tt> associated with it.
1027      * Subclasses of <tt>ClassLoader</tt> need not usually invoke this method,
1028      * because most class loaders need to override just {@link
1029      * #findClass(String)}.  </p>
1030      *
1031      * @param  name
1032      *         The <a href="#name">binary name</a> of the class
1033      *
1034      * @return  The <tt>Class</tt> object for the specified <tt>name</tt>
1035      *
1036      * @throws  ClassNotFoundException
1037      *          If the class could not be found
1038      *
1039      * @see  #ClassLoader(ClassLoader)
1040      * @see  #getParent()
1041      */
1042     protected final Class<?> findSystemClass(String name)
1043         throws ClassNotFoundException
1044     {
1045         ClassLoader system = getSystemClassLoader();
1046         if (system == null) {
1047             if (!checkName(name))
1048                 throw new ClassNotFoundException(name);
1049             Class cls = findBootstrapClass(name);
1050             if (cls == null) {
1051                 throw new ClassNotFoundException(name);
1052             }
1053             return cls;
1054         }
1055         return system.loadClass(name);
1056     }
1057 
1058     /**
1059      * Returns a class loaded by the bootstrap class loader;
1060      * or return null if not found.
1061      */
1062     private Class findBootstrapClassOrNull(String name)
1063     {
1064         if (!checkName(name)) return null;
1065 
1066         return findBootstrapClass(name);
1067     }
1068 
1069     // return null if not found
1070     private native Class findBootstrapClass(String name);
1071 
1072     /**
1073      * Returns the class with the given <a href="#name">binary name</a> if this
1074      * loader has been recorded by the Java virtual machine as an initiating
1075      * loader of a class with that <a href="#name">binary name</a>.  Otherwise
1076      * <tt>null</tt> is returned.  </p>
1077      *
1078      * @param  name
1079      *         The <a href="#name">binary name</a> of the class
1080      *
1081      * @return  The <tt>Class</tt> object, or <tt>null</tt> if the class has
1082      *          not been loaded
1083      *
1084      * @since  1.1
1085      */
1086     protected final Class<?> findLoadedClass(String name) {
1087         if (!checkName(name))
1088             return null;
1089         return findLoadedClass0(name);
1090     }
1091 
1092     private native final Class findLoadedClass0(String name);
1093 
1094     /**
1095      * Sets the signers of a class.  This should be invoked after defining a
1096      * class.  </p>
1097      *
1098      * @param  c
1099      *         The <tt>Class</tt> object
1100      *
1101      * @param  signers
1102      *         The signers for the class
1103      *
1104      * @since  1.1
1105      */
1106     protected final void setSigners(Class<?> c, Object[] signers) {
1107         c.setSigners(signers);
1108     }
1109 
1110 
1111     // -- Resource --
1112 
1113     /**
1114      * Finds the resource with the given name.  A resource is some data
1115      * (images, audio, text, etc) that can be accessed by class code in a way
1116      * that is independent of the location of the code.
1117      *
1118      * <p> The name of a resource is a '<tt>/</tt>'-separated path name that
1119      * identifies the resource.
1120      *
1121      * <p> This method will first search the parent class loader for the
1122      * resource; if the parent is <tt>null</tt> the path of the class loader
1123      * built-in to the virtual machine is searched.  That failing, this method
1124      * will invoke {@link #findResource(String)} to find the resource.  </p>
1125      *
1126      * @param  name
1127      *         The resource name
1128      *
1129      * @return  A <tt>URL</tt> object for reading the resource, or
1130      *          <tt>null</tt> if the resource could not be found or the invoker
1131      *          doesn't have adequate  privileges to get the resource.
1132      *
1133      * @since  1.1
1134      */
1135     public URL getResource(String name) {
1136         URL url;
1137         if (parent != null) {
1138             url = parent.getResource(name);
1139         } else {
1140             url = getBootstrapResource(name);
1141         }
1142         if (url == null) {
1143             url = findResource(name);
1144         }
1145         return url;
1146     }
1147 
1148     /**
1149      * Finds all the resources with the given name. A resource is some data
1150      * (images, audio, text, etc) that can be accessed by class code in a way
1151      * that is independent of the location of the code.
1152      *
1153      * <p>The name of a resource is a <tt>/</tt>-separated path name that
1154      * identifies the resource.
1155      *
1156      * <p> The search order is described in the documentation for {@link
1157      * #getResource(String)}.  </p>
1158      *
1159      * @param  name
1160      *         The resource name
1161      *
1162      * @return  An enumeration of {@link java.net.URL <tt>URL</tt>} objects for
1163      *          the resource.  If no resources could  be found, the enumeration
1164      *          will be empty.  Resources that the class loader doesn't have
1165      *          access to will not be in the enumeration.
1166      *
1167      * @throws  IOException
1168      *          If I/O errors occur
1169      *
1170      * @see  #findResources(String)
1171      *
1172      * @since  1.2
1173      */
1174     public Enumeration<URL> getResources(String name) throws IOException {
1175         Enumeration[] tmp = new Enumeration[2];
1176         if (parent != null) {
1177             tmp[0] = parent.getResources(name);
1178         } else {
1179             tmp[0] = getBootstrapResources(name);
1180         }
1181         tmp[1] = findResources(name);
1182 
1183         return new CompoundEnumeration<>(tmp);
1184     }
1185 
1186     /**
1187      * Finds the resource with the given name. Class loader implementations
1188      * should override this method to specify where to find resources.  </p>
1189      *
1190      * @param  name
1191      *         The resource name
1192      *
1193      * @return  A <tt>URL</tt> object for reading the resource, or
1194      *          <tt>null</tt> if the resource could not be found
1195      *
1196      * @since  1.2
1197      */
1198     protected URL findResource(String name) {
1199         return null;
1200     }
1201 
1202     /**
1203      * Returns an enumeration of {@link java.net.URL <tt>URL</tt>} objects
1204      * representing all the resources with the given name. Class loader
1205      * implementations should override this method to specify where to load
1206      * resources from.  </p>
1207      *
1208      * @param  name
1209      *         The resource name
1210      *
1211      * @return  An enumeration of {@link java.net.URL <tt>URL</tt>} objects for
1212      *          the resources
1213      *
1214      * @throws  IOException
1215      *          If I/O errors occur
1216      *
1217      * @since  1.2
1218      */
1219     protected Enumeration<URL> findResources(String name) throws IOException {
1220         return java.util.Collections.emptyEnumeration();
1221     }
1222 
1223     // index 0: java.lang.ClassLoader.class
1224     // index 1: the immediate caller of index 0.
1225     // index 2: the immediate caller of index 1.
1226     private static native Class<? extends ClassLoader> getCaller(int index);
1227 
1228     /**
1229      * Registers the caller as parallel capable.</p>
1230      * The registration succeeds if and only if all of the following
1231      * conditions are met: <br>
1232      * 1. no instance of the caller has been created</p>
1233      * 2. all of the super classes (except class Object) of the caller are
1234      * registered as parallel capable</p>
1235      * Note that once a class loader is registered as parallel capable, there
1236      * is no way to change it back. </p>
1237      *
1238      * @return  true if the caller is successfully registered as
1239      *          parallel capable and false if otherwise.
1240      *
1241      * @since   1.7
1242      */
1243     protected static boolean registerAsParallelCapable() {
1244         return ParallelLoaders.register(getCaller(1));
1245     }
1246 
1247     /**
1248      * Find a resource of the specified name from the search path used to load
1249      * classes.  This method locates the resource through the system class
1250      * loader (see {@link #getSystemClassLoader()}).  </p>
1251      *
1252      * @param  name
1253      *         The resource name
1254      *
1255      * @return  A {@link java.net.URL <tt>URL</tt>} object for reading the
1256      *          resource, or <tt>null</tt> if the resource could not be found
1257      *
1258      * @since  1.1
1259      */
1260     public static URL getSystemResource(String name) {
1261         ClassLoader system = getSystemClassLoader();
1262         if (system == null) {
1263             return getBootstrapResource(name);
1264         }
1265         return system.getResource(name);
1266     }
1267 
1268     /**
1269      * Finds all resources of the specified name from the search path used to
1270      * load classes.  The resources thus found are returned as an
1271      * {@link java.util.Enumeration <tt>Enumeration</tt>} of {@link
1272      * java.net.URL <tt>URL</tt>} objects.
1273      *
1274      * <p> The search order is described in the documentation for {@link
1275      * #getSystemResource(String)}.  </p>
1276      *
1277      * @param  name
1278      *         The resource name
1279      *
1280      * @return  An enumeration of resource {@link java.net.URL <tt>URL</tt>}
1281      *          objects
1282      *
1283      * @throws  IOException
1284      *          If I/O errors occur
1285 
1286      * @since  1.2
1287      */
1288     public static Enumeration<URL> getSystemResources(String name)
1289         throws IOException
1290     {
1291         ClassLoader system = getSystemClassLoader();
1292         if (system == null) {
1293             return getBootstrapResources(name);
1294         }
1295         return system.getResources(name);
1296     }
1297 
1298     /**
1299      * Find resources from the VM's built-in classloader.
1300      */
1301     private static URL getBootstrapResource(String name) {

1302         URLClassPath ucp = getBootstrapClassPath();
1303         Resource res = ucp.getResource(name);
1304         return res != null ? res.getURL() : null;
1305     }
1306 
1307     /**
1308      * Find resources from the VM's built-in classloader.
1309      */
1310     private static Enumeration<URL> getBootstrapResources(String name)
1311         throws IOException
1312     {
1313         final Enumeration<Resource> e =
1314             getBootstrapClassPath().getResources(name);
1315         return new Enumeration<URL> () {
1316             public URL nextElement() {
1317                 return e.nextElement().getURL();
1318             }
1319             public boolean hasMoreElements() {
1320                 return e.hasMoreElements();
1321             }
1322         };
1323     }
1324 
1325     // Returns the URLClassPath that is used for finding system resources.
1326     static URLClassPath getBootstrapClassPath() {
1327         return sun.misc.Launcher.getBootstrapClassPath();
1328     }
1329 
1330 
1331     /**
1332      * Returns an input stream for reading the specified resource.
1333      *
1334      * <p> The search order is described in the documentation for {@link
1335      * #getResource(String)}.  </p>
1336      *
1337      * @param  name
1338      *         The resource name
1339      *
1340      * @return  An input stream for reading the resource, or <tt>null</tt>
1341      *          if the resource could not be found
1342      *
1343      * @since  1.1
1344      */
1345     public InputStream getResourceAsStream(String name) {
1346         URL url = getResource(name);
1347         try {
1348             return url != null ? url.openStream() : null;
1349         } catch (IOException e) {
1350             return null;
1351         }
1352     }
1353 
1354     /**
1355      * Open for reading, a resource of the specified name from the search path
1356      * used to load classes.  This method locates the resource through the
1357      * system class loader (see {@link #getSystemClassLoader()}).  </p>
1358      *
1359      * @param  name
1360      *         The resource name
1361      *
1362      * @return  An input stream for reading the resource, or <tt>null</tt>
1363      *          if the resource could not be found
1364      *
1365      * @since  1.1
1366      */
1367     public static InputStream getSystemResourceAsStream(String name) {
1368         URL url = getSystemResource(name);
1369         try {
1370             return url != null ? url.openStream() : null;
1371         } catch (IOException e) {
1372             return null;
1373         }
1374     }
1375 
1376 
1377     // -- Hierarchy --
1378 
1379     /**
1380      * Returns the parent class loader for delegation. Some implementations may
1381      * use <tt>null</tt> to represent the bootstrap class loader. This method
1382      * will return <tt>null</tt> in such implementations if this class loader's
1383      * parent is the bootstrap class loader.
1384      *
1385      * <p> If a security manager is present, and the invoker's class loader is
1386      * not <tt>null</tt> and is not an ancestor of this class loader, then this
1387      * method invokes the security manager's {@link
1388      * SecurityManager#checkPermission(java.security.Permission)
1389      * <tt>checkPermission</tt>} method with a {@link
1390      * RuntimePermission#RuntimePermission(String)
1391      * <tt>RuntimePermission("getClassLoader")</tt>} permission to verify
1392      * access to the parent class loader is permitted.  If not, a
1393      * <tt>SecurityException</tt> will be thrown.  </p>
1394      *
1395      * @return  The parent <tt>ClassLoader</tt>
1396      *
1397      * @throws  SecurityException
1398      *          If a security manager exists and its <tt>checkPermission</tt>
1399      *          method doesn't allow access to this class loader's parent class
1400      *          loader.
1401      *
1402      * @since  1.2
1403      */
1404     public final ClassLoader getParent() {
1405         if (parent == null)
1406             return null;
1407         SecurityManager sm = System.getSecurityManager();
1408         if (sm != null) {
1409             ClassLoader ccl = getCallerClassLoader();
1410             if (ccl != null && !isAncestor(ccl)) {
1411                 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
1412             }
1413         }
1414         return parent;
1415     }
1416 
1417     /**
1418      * Returns the system class loader for delegation.  This is the default
1419      * delegation parent for new <tt>ClassLoader</tt> instances, and is
1420      * typically the class loader used to start the application.
1421      *
1422      * <p> This method is first invoked early in the runtime's startup
1423      * sequence, at which point it creates the system class loader and sets it
1424      * as the context class loader of the invoking <tt>Thread</tt>.
1425      *
1426      * <p> The default system class loader is an implementation-dependent
1427      * instance of this class.
1428      *
1429      * <p> If the system property "<tt>java.system.class.loader</tt>" is defined
1430      * when this method is first invoked then the value of that property is
1431      * taken to be the name of a class that will be returned as the system
1432      * class loader.  The class is loaded using the default system class loader
1433      * and must define a public constructor that takes a single parameter of
1434      * type <tt>ClassLoader</tt> which is used as the delegation parent.  An
1435      * instance is then created using this constructor with the default system
1436      * class loader as the parameter.  The resulting class loader is defined
1437      * to be the system class loader.
1438      *
1439      * <p> If a security manager is present, and the invoker's class loader is
1440      * not <tt>null</tt> and the invoker's class loader is not the same as or
1441      * an ancestor of the system class loader, then this method invokes the
1442      * security manager's {@link
1443      * SecurityManager#checkPermission(java.security.Permission)
1444      * <tt>checkPermission</tt>} method with a {@link
1445      * RuntimePermission#RuntimePermission(String)
1446      * <tt>RuntimePermission("getClassLoader")</tt>} permission to verify
1447      * access to the system class loader.  If not, a
1448      * <tt>SecurityException</tt> will be thrown.  </p>
1449      *
1450      * @return  The system <tt>ClassLoader</tt> for delegation, or
1451      *          <tt>null</tt> if none
1452      *
1453      * @throws  SecurityException
1454      *          If a security manager exists and its <tt>checkPermission</tt>
1455      *          method doesn't allow access to the system class loader.
1456      *
1457      * @throws  IllegalStateException
1458      *          If invoked recursively during the construction of the class
1459      *          loader specified by the "<tt>java.system.class.loader</tt>"
1460      *          property.
1461      *
1462      * @throws  Error
1463      *          If the system property "<tt>java.system.class.loader</tt>"
1464      *          is defined but the named class could not be loaded, the
1465      *          provider class does not define the required constructor, or an
1466      *          exception is thrown by that constructor when it is invoked. The
1467      *          underlying cause of the error can be retrieved via the
1468      *          {@link Throwable#getCause()} method.
1469      *
1470      * @revised  1.4
1471      */
1472     public static ClassLoader getSystemClassLoader() {
1473         initSystemClassLoader();
1474         if (scl == null) {
1475             return null;
1476         }
1477         SecurityManager sm = System.getSecurityManager();
1478         if (sm != null) {
1479             ClassLoader ccl = getCallerClassLoader();
1480             if (ccl != null && ccl != scl && !scl.isAncestor(ccl)) {
1481                 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
1482             }
1483         }
1484         return scl;
1485     }
1486 
1487     private static synchronized void initSystemClassLoader() {
1488         if (!sclSet) {
1489             if (scl != null)
1490                 throw new IllegalStateException("recursive invocation");
1491             sun.misc.Launcher l = sun.misc.Launcher.getLauncher();
1492             if (l != null) {
1493                 Throwable oops = null;
1494                 scl = l.getClassLoader();
1495                 try {
1496                     scl = AccessController.doPrivileged(
1497                         new SystemClassLoaderAction(scl));
1498                 } catch (PrivilegedActionException pae) {
1499                     oops = pae.getCause();
1500                     if (oops instanceof InvocationTargetException) {
1501                         oops = oops.getCause();
1502                     }
1503                 }
1504                 if (oops != null) {
1505                     if (oops instanceof Error) {
1506                         throw (Error) oops;
1507                     } else {
1508                         // wrap the exception
1509                         throw new Error(oops);
1510                     }
1511                 }
1512             }
1513             sclSet = true;
1514         }
1515     }
1516 
1517     // Returns true if the specified class loader can be found in this class
1518     // loader's delegation chain.
1519     boolean isAncestor(ClassLoader cl) {
1520         ClassLoader acl = this;
1521         do {
1522             acl = acl.parent;
1523             if (cl == acl) {
1524                 return true;
1525             }
1526         } while (acl != null);
1527         return false;
1528     }
1529 
1530     // Returns the invoker's class loader, or null if none.
1531     // NOTE: This must always be invoked when there is exactly one intervening
1532     // frame from the core libraries on the stack between this method's
1533     // invocation and the desired invoker.
1534     static ClassLoader getCallerClassLoader() {
1535         // NOTE use of more generic Reflection.getCallerClass()
1536         Class caller = Reflection.getCallerClass(3);
1537         // This can be null if the VM is requesting it
1538         if (caller == null) {
1539             return null;
1540         }
1541         // Circumvent security check since this is package-private
1542         return caller.getClassLoader0();
1543     }
1544 
1545     // The class loader for the system
1546     // @GuardedBy("ClassLoader.class")
1547     private static ClassLoader scl;
1548 
1549     // Set to true once the system class loader has been set
1550     // @GuardedBy("ClassLoader.class")
1551     private static boolean sclSet;
1552 
1553 
1554     // -- Package --
1555 
1556     /**
1557      * Defines a package by name in this <tt>ClassLoader</tt>.  This allows
1558      * class loaders to define the packages for their classes. Packages must
1559      * be created before the class is defined, and package names must be
1560      * unique within a class loader and cannot be redefined or changed once
1561      * created.  </p>
1562      *
1563      * @param  name
1564      *         The package name
1565      *
1566      * @param  specTitle
1567      *         The specification title
1568      *
1569      * @param  specVersion
1570      *         The specification version
1571      *
1572      * @param  specVendor
1573      *         The specification vendor
1574      *
1575      * @param  implTitle
1576      *         The implementation title
1577      *
1578      * @param  implVersion
1579      *         The implementation version
1580      *
1581      * @param  implVendor
1582      *         The implementation vendor
1583      *
1584      * @param  sealBase
1585      *         If not <tt>null</tt>, then this package is sealed with
1586      *         respect to the given code source {@link java.net.URL
1587      *         <tt>URL</tt>}  object.  Otherwise, the package is not sealed.
1588      *
1589      * @return  The newly defined <tt>Package</tt> object
1590      *
1591      * @throws  IllegalArgumentException
1592      *          If package name duplicates an existing package either in this
1593      *          class loader or one of its ancestors
1594      *
1595      * @since  1.2
1596      */
1597     protected Package definePackage(String name, String specTitle,
1598                                     String specVersion, String specVendor,
1599                                     String implTitle, String implVersion,
1600                                     String implVendor, URL sealBase)
1601         throws IllegalArgumentException
1602     {
1603         synchronized (packages) {
1604             Package pkg = getPackage(name);
1605             if (pkg != null) {
1606                 throw new IllegalArgumentException(name);
1607             }
1608             pkg = new Package(name, specTitle, specVersion, specVendor,
1609                               implTitle, implVersion, implVendor,
1610                               sealBase, this);
1611             packages.put(name, pkg);
1612             return pkg;
1613         }
1614     }
1615 
1616     /**
1617      * Returns a <tt>Package</tt> that has been defined by this class loader
1618      * or any of its ancestors.  </p>
1619      *
1620      * @param  name
1621      *         The package name
1622      *
1623      * @return  The <tt>Package</tt> corresponding to the given name, or
1624      *          <tt>null</tt> if not found
1625      *
1626      * @since  1.2
1627      */
1628     protected Package getPackage(String name) {
1629         synchronized (packages) {
1630             Package pkg = packages.get(name);
1631             if (pkg == null) {
1632                 if (parent != null) {
1633                     pkg = parent.getPackage(name);
1634                 } else {
1635                     pkg = Package.getSystemPackage(name);
1636                 }
1637                 if (pkg != null) {
1638                     packages.put(name, pkg);
1639                 }
1640             }
1641             return pkg;
1642         }
1643     }
1644 
1645     /**
1646      * Returns all of the <tt>Packages</tt> defined by this class loader and
1647      * its ancestors.  </p>
1648      *
1649      * @return  The array of <tt>Package</tt> objects defined by this
1650      *          <tt>ClassLoader</tt>
1651      *
1652      * @since  1.2
1653      */
1654     protected Package[] getPackages() {
1655         Map<String, Package> map;
1656         synchronized (packages) {
1657             map = new HashMap<>(packages);
1658         }
1659         Package[] pkgs;
1660         if (parent != null) {
1661             pkgs = parent.getPackages();
1662         } else {
1663             pkgs = Package.getSystemPackages();
1664         }
1665         if (pkgs != null) {
1666             for (int i = 0; i < pkgs.length; i++) {
1667                 String pkgName = pkgs[i].getName();
1668                 if (map.get(pkgName) == null) {
1669                     map.put(pkgName, pkgs[i]);
1670                 }
1671             }
1672         }
1673         return map.values().toArray(new Package[map.size()]);
1674     }
1675 
1676 
1677     // -- Native library access --
1678 
1679     /**
1680      * Returns the absolute path name of a native library.  The VM invokes this
1681      * method to locate the native libraries that belong to classes loaded with
1682      * this class loader. If this method returns <tt>null</tt>, the VM
1683      * searches the library along the path specified as the
1684      * "<tt>java.library.path</tt>" property.  </p>
1685      *
1686      * @param  libname
1687      *         The library name
1688      *
1689      * @return  The absolute path of the native library
1690      *
1691      * @see  System#loadLibrary(String)
1692      * @see  System#mapLibraryName(String)
1693      *
1694      * @since  1.2
1695      */
1696     protected String findLibrary(String libname) {
1697         return null;
1698     }
1699 
1700     /**
1701      * The inner class NativeLibrary denotes a loaded native library instance.
1702      * Every classloader contains a vector of loaded native libraries in the
1703      * private field <tt>nativeLibraries</tt>.  The native libraries loaded
1704      * into the system are entered into the <tt>systemNativeLibraries</tt>
1705      * vector.
1706      *
1707      * <p> Every native library requires a particular version of JNI. This is
1708      * denoted by the private <tt>jniVersion</tt> field.  This field is set by
1709      * the VM when it loads the library, and used by the VM to pass the correct
1710      * version of JNI to the native methods.  </p>
1711      *
1712      * @see      ClassLoader
1713      * @since    1.2
1714      */
1715     static class NativeLibrary {
1716         // opaque handle to native library, used in native code.
1717         long handle;
1718         // the version of JNI environment the native library requires.
1719         private int jniVersion;
1720         // the class from which the library is loaded, also indicates
1721         // the loader this native library belongs.
1722         private Class fromClass;
1723         // the canonicalized name of the native library.
1724         String name;
1725 
1726         native void load(String name);
1727         native long find(String name);
1728         native void unload();
1729 
1730         public NativeLibrary(Class fromClass, String name) {
1731             this.name = name;
1732             this.fromClass = fromClass;
1733         }
1734 
1735         protected void finalize() {
1736             synchronized (loadedLibraryNames) {
1737                 if (fromClass.getClassLoader() != null && handle != 0) {
1738                     /* remove the native library name */
1739                     int size = loadedLibraryNames.size();
1740                     for (int i = 0; i < size; i++) {
1741                         if (name.equals(loadedLibraryNames.elementAt(i))) {
1742                             loadedLibraryNames.removeElementAt(i);
1743                             break;
1744                         }
1745                     }
1746                     /* unload the library. */
1747                     ClassLoader.nativeLibraryContext.push(this);
1748                     try {
1749                         unload();
1750                     } finally {
1751                         ClassLoader.nativeLibraryContext.pop();
1752                     }
1753                 }
1754             }
1755         }
1756         // Invoked in the VM to determine the context class in
1757         // JNI_Load/JNI_Unload
1758         static Class getFromClass() {
1759             return ClassLoader.nativeLibraryContext.peek().fromClass;
1760         }
1761     }
1762 
1763     // All native library names we've loaded.
1764     private static Vector<String> loadedLibraryNames = new Vector<>();
1765 
1766     // Native libraries belonging to system classes.
1767     private static Vector<NativeLibrary> systemNativeLibraries
1768         = new Vector<>();
1769 
1770     // Native libraries associated with the class loader.
1771     private Vector<NativeLibrary> nativeLibraries = new Vector<>();
1772 
1773     // native libraries being loaded/unloaded.
1774     private static Stack<NativeLibrary> nativeLibraryContext = new Stack<>();
1775 
1776     // The paths searched for libraries
1777     private static String usr_paths[];
1778     private static String sys_paths[];
1779 
1780     private static String[] initializePath(String propname) {
1781         String ldpath = System.getProperty(propname, "");
1782         String ps = File.pathSeparator;
1783         int ldlen = ldpath.length();
1784         int i, j, n;
1785         // Count the separators in the path
1786         i = ldpath.indexOf(ps);
1787         n = 0;
1788         while (i >= 0) {
1789             n++;
1790             i = ldpath.indexOf(ps, i + 1);
1791         }
1792 
1793         // allocate the array of paths - n :'s = n + 1 path elements
1794         String[] paths = new String[n + 1];
1795 
1796         // Fill the array with paths from the ldpath
1797         n = i = 0;
1798         j = ldpath.indexOf(ps);
1799         while (j >= 0) {
1800             if (j - i > 0) {
1801                 paths[n++] = ldpath.substring(i, j);
1802             } else if (j - i == 0) {
1803                 paths[n++] = ".";
1804             }
1805             i = j + 1;
1806             j = ldpath.indexOf(ps, i);
1807         }
1808         paths[n] = ldpath.substring(i, ldlen);
1809         return paths;
1810     }
1811 
1812     // Invoked in the java.lang.Runtime class to implement load and loadLibrary.
1813     static void loadLibrary(Class fromClass, String name,
1814                             boolean isAbsolute) {

1815         ClassLoader loader =
1816             (fromClass == null) ? null : fromClass.getClassLoader();
1817         if (sys_paths == null) {
1818             usr_paths = initializePath("java.library.path");
1819             sys_paths = initializePath("sun.boot.library.path");
1820         }
1821         if (isAbsolute) {
1822             if (loadLibrary0(fromClass, new File(name))) {
1823                 return;
1824             }
1825             throw new UnsatisfiedLinkError("Can't load library: " + name);
1826         }
1827         if (loader != null) {
1828             String libfilename = loader.findLibrary(name);
1829             if (libfilename != null) {
1830                 File libfile = new File(libfilename);
1831                 if (!libfile.isAbsolute()) {
1832                     throw new UnsatisfiedLinkError(
1833     "ClassLoader.findLibrary failed to return an absolute path: " + libfilename);
1834                 }
1835                 if (loadLibrary0(fromClass, libfile)) {
1836                     return;
1837                 }
1838                 throw new UnsatisfiedLinkError("Can't load " + libfilename);
1839             }
1840         }
1841         for (int i = 0 ; i < sys_paths.length ; i++) {
1842             File libfile = new File(sys_paths[i], System.mapLibraryName(name));
1843             if (loadLibrary0(fromClass, libfile)) {
1844                 return;
1845             }
1846         }
1847         if (loader != null) {
1848             for (int i = 0 ; i < usr_paths.length ; i++) {
1849                 File libfile = new File(usr_paths[i],
1850                                         System.mapLibraryName(name));
1851                 if (loadLibrary0(fromClass, libfile)) {
1852                     return;
1853                 }
1854             }
1855         }
1856         // Oops, it failed
1857         throw new UnsatisfiedLinkError("no " + name + " in java.library.path");
1858     }
1859 
1860     private static boolean loadLibrary0(Class fromClass, final File file) {
1861         boolean exists = AccessController.doPrivileged(
1862             new PrivilegedAction<Object>() {
1863                 public Object run() {
1864                     return file.exists() ? Boolean.TRUE : null;
1865                 }})
1866             != null;
1867         if (!exists) {
1868             return false;
1869         }
1870         String name;
1871         try {
1872             name = file.getCanonicalPath();
1873         } catch (IOException e) {
1874             return false;
1875         }
1876         ClassLoader loader =
1877             (fromClass == null) ? null : fromClass.getClassLoader();
1878         Vector<NativeLibrary> libs =
1879             loader != null ? loader.nativeLibraries : systemNativeLibraries;
1880         synchronized (libs) {
1881             int size = libs.size();
1882             for (int i = 0; i < size; i++) {
1883                 NativeLibrary lib = libs.elementAt(i);
1884                 if (name.equals(lib.name)) {
1885                     return true;
1886                 }
1887             }
1888 
1889             synchronized (loadedLibraryNames) {
1890                 if (loadedLibraryNames.contains(name)) {
1891                     throw new UnsatisfiedLinkError
1892                         ("Native Library " +
1893                          name +
1894                          " already loaded in another classloader");
1895                 }
1896                 /* If the library is being loaded (must be by the same thread,
1897                  * because Runtime.load and Runtime.loadLibrary are
1898                  * synchronous). The reason is can occur is that the JNI_OnLoad
1899                  * function can cause another loadLibrary invocation.
1900                  *
1901                  * Thus we can use a static stack to hold the list of libraries
1902                  * we are loading.
1903                  *
1904                  * If there is a pending load operation for the library, we
1905                  * immediately return success; otherwise, we raise
1906                  * UnsatisfiedLinkError.
1907                  */
1908                 int n = nativeLibraryContext.size();
1909                 for (int i = 0; i < n; i++) {
1910                     NativeLibrary lib = nativeLibraryContext.elementAt(i);
1911                     if (name.equals(lib.name)) {
1912                         if (loader == lib.fromClass.getClassLoader()) {
1913                             return true;
1914                         } else {
1915                             throw new UnsatisfiedLinkError
1916                                 ("Native Library " +
1917                                  name +
1918                                  " is being loaded in another classloader");
1919                         }
1920                     }
1921                 }
1922                 NativeLibrary lib = new NativeLibrary(fromClass, name);
1923                 nativeLibraryContext.push(lib);
1924                 try {
1925                     lib.load(name);
1926                 } finally {
1927                     nativeLibraryContext.pop();
1928                 }
1929                 if (lib.handle != 0) {
1930                     loadedLibraryNames.addElement(name);
1931                     libs.addElement(lib);
1932                     return true;
1933                 }
1934                 return false;
1935             }
1936         }
1937     }
1938 
1939     // Invoked in the VM class linking code.
1940     static long findNative(ClassLoader loader, String name) {
1941         Vector<NativeLibrary> libs =
1942             loader != null ? loader.nativeLibraries : systemNativeLibraries;
1943         synchronized (libs) {
1944             int size = libs.size();
1945             for (int i = 0; i < size; i++) {
1946                 NativeLibrary lib = libs.elementAt(i);
1947                 long entry = lib.find(name);
1948                 if (entry != 0)
1949                     return entry;
1950             }
1951         }
1952         return 0;
1953     }
1954 
1955 
1956     // -- Assertion management --
1957 
1958     final Object assertionLock;
1959 
1960     // The default toggle for assertion checking.
1961     // @GuardedBy("assertionLock")
1962     private boolean defaultAssertionStatus = false;
1963 
1964     // Maps String packageName to Boolean package default assertion status Note
1965     // that the default package is placed under a null map key.  If this field
1966     // is null then we are delegating assertion status queries to the VM, i.e.,
1967     // none of this ClassLoader's assertion status modification methods have
1968     // been invoked.
1969     // @GuardedBy("assertionLock")
1970     private Map<String, Boolean> packageAssertionStatus = null;
1971 
1972     // Maps String fullyQualifiedClassName to Boolean assertionStatus If this
1973     // field is null then we are delegating assertion status queries to the VM,
1974     // i.e., none of this ClassLoader's assertion status modification methods
1975     // have been invoked.
1976     // @GuardedBy("assertionLock")
1977     Map<String, Boolean> classAssertionStatus = null;
1978 
1979     /**
1980      * Sets the default assertion status for this class loader.  This setting
1981      * determines whether classes loaded by this class loader and initialized
1982      * in the future will have assertions enabled or disabled by default.
1983      * This setting may be overridden on a per-package or per-class basis by
1984      * invoking {@link #setPackageAssertionStatus(String, boolean)} or {@link
1985      * #setClassAssertionStatus(String, boolean)}.  </p>
1986      *
1987      * @param  enabled
1988      *         <tt>true</tt> if classes loaded by this class loader will
1989      *         henceforth have assertions enabled by default, <tt>false</tt>
1990      *         if they will have assertions disabled by default.
1991      *
1992      * @since  1.4
1993      */
1994     public void setDefaultAssertionStatus(boolean enabled) {
1995         synchronized (assertionLock) {
1996             if (classAssertionStatus == null)
1997                 initializeJavaAssertionMaps();
1998 
1999             defaultAssertionStatus = enabled;
2000         }
2001     }
2002 
2003     /**
2004      * Sets the package default assertion status for the named package.  The
2005      * package default assertion status determines the assertion status for
2006      * classes initialized in the future that belong to the named package or
2007      * any of its "subpackages".
2008      *
2009      * <p> A subpackage of a package named p is any package whose name begins
2010      * with "<tt>p.</tt>".  For example, <tt>javax.swing.text</tt> is a
2011      * subpackage of <tt>javax.swing</tt>, and both <tt>java.util</tt> and
2012      * <tt>java.lang.reflect</tt> are subpackages of <tt>java</tt>.
2013      *
2014      * <p> In the event that multiple package defaults apply to a given class,
2015      * the package default pertaining to the most specific package takes
2016      * precedence over the others.  For example, if <tt>javax.lang</tt> and
2017      * <tt>javax.lang.reflect</tt> both have package defaults associated with
2018      * them, the latter package default applies to classes in
2019      * <tt>javax.lang.reflect</tt>.
2020      *
2021      * <p> Package defaults take precedence over the class loader's default
2022      * assertion status, and may be overridden on a per-class basis by invoking
2023      * {@link #setClassAssertionStatus(String, boolean)}.  </p>
2024      *
2025      * @param  packageName
2026      *         The name of the package whose package default assertion status
2027      *         is to be set. A <tt>null</tt> value indicates the unnamed
2028      *         package that is "current"
2029      *         (<a href="http://java.sun.com/docs/books/jls/">Java Language
2030      *         Specification</a>, section 7.4.2).
2031      *
2032      * @param  enabled
2033      *         <tt>true</tt> if classes loaded by this classloader and
2034      *         belonging to the named package or any of its subpackages will
2035      *         have assertions enabled by default, <tt>false</tt> if they will
2036      *         have assertions disabled by default.
2037      *
2038      * @since  1.4
2039      */
2040     public void setPackageAssertionStatus(String packageName,
2041                                           boolean enabled) {
2042         synchronized (assertionLock) {
2043             if (packageAssertionStatus == null)
2044                 initializeJavaAssertionMaps();
2045 
2046             packageAssertionStatus.put(packageName, enabled);
2047         }
2048     }
2049 
2050     /**
2051      * Sets the desired assertion status for the named top-level class in this
2052      * class loader and any nested classes contained therein.  This setting
2053      * takes precedence over the class loader's default assertion status, and
2054      * over any applicable per-package default.  This method has no effect if
2055      * the named class has already been initialized.  (Once a class is
2056      * initialized, its assertion status cannot change.)
2057      *
2058      * <p> If the named class is not a top-level class, this invocation will
2059      * have no effect on the actual assertion status of any class. </p>
2060      *
2061      * @param  className
2062      *         The fully qualified class name of the top-level class whose
2063      *         assertion status is to be set.
2064      *
2065      * @param  enabled
2066      *         <tt>true</tt> if the named class is to have assertions
2067      *         enabled when (and if) it is initialized, <tt>false</tt> if the
2068      *         class is to have assertions disabled.
2069      *
2070      * @since  1.4
2071      */
2072     public void setClassAssertionStatus(String className, boolean enabled) {
2073         synchronized (assertionLock) {
2074             if (classAssertionStatus == null)
2075                 initializeJavaAssertionMaps();
2076 
2077             classAssertionStatus.put(className, enabled);
2078         }
2079     }
2080 
2081     /**
2082      * Sets the default assertion status for this class loader to
2083      * <tt>false</tt> and discards any package defaults or class assertion
2084      * status settings associated with the class loader.  This method is
2085      * provided so that class loaders can be made to ignore any command line or
2086      * persistent assertion status settings and "start with a clean slate."
2087      * </p>
2088      *
2089      * @since  1.4
2090      */
2091     public void clearAssertionStatus() {
2092         /*
2093          * Whether or not "Java assertion maps" are initialized, set
2094          * them to empty maps, effectively ignoring any present settings.
2095          */
2096         synchronized (assertionLock) {
2097             classAssertionStatus = new HashMap<>();
2098             packageAssertionStatus = new HashMap<>();
2099             defaultAssertionStatus = false;
2100         }
2101     }
2102 
2103     /**
2104      * Returns the assertion status that would be assigned to the specified
2105      * class if it were to be initialized at the time this method is invoked.
2106      * If the named class has had its assertion status set, the most recent
2107      * setting will be returned; otherwise, if any package default assertion
2108      * status pertains to this class, the most recent setting for the most
2109      * specific pertinent package default assertion status is returned;
2110      * otherwise, this class loader's default assertion status is returned.
2111      * </p>
2112      *
2113      * @param  className
2114      *         The fully qualified class name of the class whose desired
2115      *         assertion status is being queried.
2116      *
2117      * @return  The desired assertion status of the specified class.
2118      *
2119      * @see  #setClassAssertionStatus(String, boolean)
2120      * @see  #setPackageAssertionStatus(String, boolean)
2121      * @see  #setDefaultAssertionStatus(boolean)
2122      *
2123      * @since  1.4
2124      */
2125     boolean desiredAssertionStatus(String className) {
2126         synchronized (assertionLock) {
2127             // assert classAssertionStatus   != null;
2128             // assert packageAssertionStatus != null;
2129 
2130             // Check for a class entry
2131             Boolean result = classAssertionStatus.get(className);
2132             if (result != null)
2133                 return result.booleanValue();
2134 
2135             // Check for most specific package entry
2136             int dotIndex = className.lastIndexOf(".");
2137             if (dotIndex < 0) { // default package
2138                 result = packageAssertionStatus.get(null);
2139                 if (result != null)
2140                     return result.booleanValue();
2141             }
2142             while(dotIndex > 0) {
2143                 className = className.substring(0, dotIndex);
2144                 result = packageAssertionStatus.get(className);
2145                 if (result != null)
2146                     return result.booleanValue();
2147                 dotIndex = className.lastIndexOf(".", dotIndex-1);
2148             }
2149 
2150             // Return the classloader default
2151             return defaultAssertionStatus;
2152         }
2153     }
2154 
2155     // Set up the assertions with information provided by the VM.
2156     // Note: Should only be called inside a synchronized block
2157     private void initializeJavaAssertionMaps() {
2158         // assert Thread.holdsLock(assertionLock);
2159 
2160         classAssertionStatus = new HashMap<>();
2161         packageAssertionStatus = new HashMap<>();
2162         AssertionStatusDirectives directives = retrieveDirectives();
2163 
2164         for(int i = 0; i < directives.classes.length; i++)
2165             classAssertionStatus.put(directives.classes[i],
2166                                      directives.classEnabled[i]);
2167 
2168         for(int i = 0; i < directives.packages.length; i++)
2169             packageAssertionStatus.put(directives.packages[i],
2170                                        directives.packageEnabled[i]);
2171 
2172         defaultAssertionStatus = directives.deflt;
2173     }
2174 
2175     // Retrieves the assertion directives from the VM.
2176     private static native AssertionStatusDirectives retrieveDirectives();
2177 }
2178 
2179 
2180 class SystemClassLoaderAction
2181     implements PrivilegedExceptionAction<ClassLoader> {
2182     private ClassLoader parent;
2183 
2184     SystemClassLoaderAction(ClassLoader parent) {
2185         this.parent = parent;
2186     }
2187 
2188     public ClassLoader run() throws Exception {
2189         String cls = System.getProperty("java.system.class.loader");
2190         if (cls == null) {
2191             return parent;
2192         }
2193 
2194         Constructor ctor = Class.forName(cls, true, parent)
2195             .getDeclaredConstructor(new Class[] { ClassLoader.class });
2196         ClassLoader sys = (ClassLoader) ctor.newInstance(
2197             new Object[] { parent });
2198         Thread.currentThread().setContextClassLoader(sys);
2199         return sys;
2200     }
2201 }
--- EOF ---