/* * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang; import java.io.InputStream; import java.io.IOException; import java.io.File; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.net.MalformedURLException; import java.net.URL; import java.security.AccessController; import java.security.AccessControlContext; import java.security.CodeSource; import java.security.Policy; import java.security.PrivilegedAction; import java.security.PrivilegedActionException; import java.security.PrivilegedExceptionAction; import java.security.ProtectionDomain; import java.security.cert.Certificate; import java.util.Collections; import java.util.Enumeration; import java.util.HashMap; import java.util.HashSet; import java.util.Set; import java.util.Stack; import java.util.Map; import java.util.Vector; import java.util.Hashtable; import java.util.WeakHashMap; import java.util.concurrent.ConcurrentHashMap; import sun.misc.ClassFileTransformer; import sun.misc.CompoundEnumeration; import sun.misc.Resource; import sun.misc.URLClassPath; import sun.misc.VM; import sun.reflect.Reflection; import sun.security.util.SecurityConstants; /** * A class loader is an object that is responsible for loading classes. The * class ClassLoader is an abstract class. Given the binary name of a class, a class loader should attempt to * locate or generate data that constitutes a definition for the class. A * typical strategy is to transform the name into a file name and then read a * "class file" of that name from a file system. * *

Every {@link Class Class} object contains a {@link * Class#getClassLoader() reference} to the ClassLoader that defined * it. * *

Class objects for array classes are not created by class * loaders, but are created automatically as required by the Java runtime. * The class loader for an array class, as returned by {@link * Class#getClassLoader()} is the same as the class loader for its element * type; if the element type is a primitive type, then the array class has no * class loader. * *

Applications implement subclasses of ClassLoader in order to * extend the manner in which the Java virtual machine dynamically loads * classes. * *

Class loaders may typically be used by security managers to indicate * security domains. * *

The ClassLoader class uses a delegation model to search for * classes and resources. Each instance of ClassLoader has an * associated parent class loader. When requested to find a class or * resource, a ClassLoader instance will delegate the search for the * class or resource to its parent class loader before attempting to find the * class or resource itself. The virtual machine's built-in class loader, * called the "bootstrap class loader", does not itself have a parent but may * serve as the parent of a ClassLoader instance. * *

Class loaders that support concurrent loading of classes are known as * parallel capable class loaders and are required to register * themselves at their class initialization time by invoking the * {@link * #registerAsParallelCapable ClassLoader.registerAsParallelCapable} * method. Note that the ClassLoader class is registered as parallel * capable by default. However, its subclasses still need to register themselves * if they are parallel capable.
* In environments in which the delegation model is not strictly * hierarchical, class loaders need to be parallel capable, otherwise class * loading can lead to deadlocks because the loader lock is held for the * duration of the class loading process (see {@link #loadClass * loadClass} methods). * *

Normally, the Java virtual machine loads classes from the local file * system in a platform-dependent manner. For example, on UNIX systems, the * virtual machine loads classes from the directory defined by the * CLASSPATH environment variable. * *

However, some classes may not originate from a file; they may originate * from other sources, such as the network, or they could be constructed by an * application. The method {@link #defineClass(String, byte[], int, int) * defineClass} converts an array of bytes into an instance of class * Class. Instances of this newly defined class can be created using * {@link Class#newInstance Class.newInstance}. * *

The methods and constructors of objects created by a class loader may * reference other classes. To determine the class(es) referred to, the Java * virtual machine invokes the {@link #loadClass loadClass} method of * the class loader that originally created the class. * *

For example, an application could create a network class loader to * download class files from a server. Sample code might look like: * *

 *   ClassLoader loader = new NetworkClassLoader(host, port);
 *   Object main = loader.loadClass("Main", true).newInstance();
 *        . . .
 *

* *

The network class loader subclass must define the methods {@link * #findClass findClass} and loadClassData to load a class * from the network. Once it has downloaded the bytes that make up the class, * it should use the method {@link #defineClass defineClass} to * create a class instance. A sample implementation is: * *

 *     class NetworkClassLoader extends ClassLoader {
 *         String host;
 *         int port;
 *
 *         public Class findClass(String name) {
 *             byte[] b = loadClassData(name);
 *             return defineClass(name, b, 0, b.length);
 *         }
 *
 *         private byte[] loadClassData(String name) {
 *             // load the class data from the connection
 *              . . .
 *         }
 *     }
 *

* *

Binary names

* *

Any class name provided as a {@link String} parameter to methods in * ClassLoader must be a binary name as defined by * The Java™ Language Specification. * *

Examples of valid class names include: *

 *   "java.lang.String"
 *   "javax.swing.JSpinner$DefaultEditor"
 *   "java.security.KeyStore$Builder$FileBuilder$1"
 *   "java.net.URLClassLoader$3$1"
 *

* * @see #resolveClass(Class) * @since 1.0 */ public abstract class ClassLoader { private static native void registerNatives(); static { registerNatives(); } // The parent class loader for delegation // Note: VM hardcoded the offset of this field, thus all new fields // must be added *after* it. private final ClassLoader parent; /** * Encapsulates the set of parallel capable loader types. */ private static class ParallelLoaders { private ParallelLoaders() {} // the set of parallel capable loader types private static final Set> loaderTypes = Collections.newSetFromMap( new WeakHashMap, Boolean>()); static { synchronized (loaderTypes) { loaderTypes.add(ClassLoader.class); } } /** * Registers the given class loader type as parallel capabale. * Returns {@code true} is successfully registered; {@code false} if * loader's super class is not registered. */ static boolean register(Class c) { synchronized (loaderTypes) { if (loaderTypes.contains(c.getSuperclass())) { // register the class loader as parallel capable // if and only if all of its super classes are. // Note: given current classloading sequence, if // the immediate super class is parallel capable, // all the super classes higher up must be too. loaderTypes.add(c); return true; } else { return false; } } } /** * Returns {@code true} if the given class loader type is * registered as parallel capable. */ static boolean isRegistered(Class c) { synchronized (loaderTypes) { return loaderTypes.contains(c); } } } // Maps class name to the corresponding lock object when the current // class loader is parallel capable. // Note: VM also uses this field to decide if the current class loader // is parallel capable and the appropriate lock object for class loading. private final ConcurrentHashMap parallelLockMap; // Hashtable that maps packages to certs private final Map package2certs; // Shared among all packages with unsigned classes private static final Certificate[] nocerts = new Certificate[0]; // The classes loaded by this class loader. The only purpose of this table // is to keep the classes from being GC'ed until the loader is GC'ed. private final Vector> classes = new Vector<>(); // The "default" domain. Set as the default ProtectionDomain on newly // created classes. private final ProtectionDomain defaultDomain = new ProtectionDomain(new CodeSource(null, (Certificate[]) null), null, this, null); // The initiating protection domains for all classes loaded by this loader private final Set domains; // Invoked by the VM to record every loaded class with this loader. void addClass(Class c) { classes.addElement(c); } // The packages defined in this class loader. Each package name is mapped // to its corresponding Package object. // @GuardedBy("itself") private final HashMap packages = new HashMap<>(); private static Void checkCreateClassLoader() { SecurityManager security = System.getSecurityManager(); if (security != null) { security.checkCreateClassLoader(); } return null; } private ClassLoader(Void unused, ClassLoader parent) { this.parent = parent; if (ParallelLoaders.isRegistered(this.getClass())) { parallelLockMap = new ConcurrentHashMap<>(); package2certs = new ConcurrentHashMap<>(); domains = Collections.synchronizedSet(new HashSet()); assertionLock = new Object(); } else { // no finer-grained lock; lock on the classloader instance parallelLockMap = null; package2certs = new Hashtable<>(); domains = new HashSet<>(); assertionLock = this; } } /** * Creates a new class loader using the specified parent class loader for * delegation. * *

If there is a security manager, its {@link * SecurityManager#checkCreateClassLoader() * checkCreateClassLoader} method is invoked. This may result in * a security exception.

* * @param parent * The parent class loader * * @throws SecurityException * If a security manager exists and its * checkCreateClassLoader method doesn't allow creation * of a new class loader. * * @since 1.2 */ protected ClassLoader(ClassLoader parent) { this(checkCreateClassLoader(), parent); } /** * Creates a new class loader using the ClassLoader returned by * the method {@link #getSystemClassLoader() * getSystemClassLoader()} as the parent class loader. * *

If there is a security manager, its {@link * SecurityManager#checkCreateClassLoader() * checkCreateClassLoader} method is invoked. This may result in * a security exception.

* * @throws SecurityException * If a security manager exists and its * checkCreateClassLoader method doesn't allow creation * of a new class loader. */ protected ClassLoader() { this(checkCreateClassLoader(), getSystemClassLoader()); } // -- Class -- /** * Loads the class with the specified binary name. * This method searches for classes in the same manner as the {@link * #loadClass(String, boolean)} method. It is invoked by the Java virtual * machine to resolve class references. Invoking this method is equivalent * to invoking {@link #loadClass(String, boolean) loadClass(name, * false)}.

* * @param name * The binary name of the class * * @return The resulting Class object * * @throws ClassNotFoundException * If the class was not found */ public Class loadClass(String name) throws ClassNotFoundException { return loadClass(name, false); } /** * Loads the class with the specified binary name. The * default implementation of this method searches for classes in the * following order: * *

Invoke {@link #findLoadedClass(String)} to check if the class * has already been loaded.
Invoke the {@link #loadClass(String) loadClass} method * on the parent class loader. If the parent is null the class * loader built-in to the virtual machine is used, instead.
Invoke the {@link #findClass(String)} method to find the * class.

* *

If the class was found using the above steps, and the * resolve flag is true, this method will then invoke the {@link * #resolveClass(Class)} method on the resulting Class object. * *

Subclasses of ClassLoader are encouraged to override {@link * #findClass(String)}, rather than this method.

* *

Unless overridden, this method synchronizes on the result of * {@link #getClassLoadingLock getClassLoadingLock} method * during the entire class loading process. * * @param name * The binary name of the class * * @param resolve * If true then resolve the class * * @return The resulting Class object * * @throws ClassNotFoundException * If the class could not be found */ protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException { synchronized (getClassLoadingLock(name)) { // First, check if the class has already been loaded Class c = findLoadedClass(name); if (c == null) { long t0 = System.nanoTime(); try { if (parent != null) { c = parent.loadClass(name, false); } else { c = findBootstrapClassOrNull(name); } } catch (ClassNotFoundException e) { // ClassNotFoundException thrown if class not found // from the non-null parent class loader } if (c == null) { // If still not found, then invoke findClass in order // to find the class. long t1 = System.nanoTime(); c = findClass(name); // this is the defining class loader; record the stats sun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0); sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1); sun.misc.PerfCounter.getFindClasses().increment(); } } if (resolve) { resolveClass(c); } return c; } } /** * Returns the lock object for class loading operations. * For backward compatibility, the default implementation of this method * behaves as follows. If this ClassLoader object is registered as * parallel capable, the method returns a dedicated object associated * with the specified class name. Otherwise, the method returns this * ClassLoader object.

* * @param className * The name of the to-be-loaded class * * @return the lock for class loading operations * * @throws NullPointerException * If registered as parallel capable and className is null * * @see #loadClass(String, boolean) * * @since 1.7 */ protected Object getClassLoadingLock(String className) { Object lock = this; if (parallelLockMap != null) { Object newLock = new Object(); lock = parallelLockMap.putIfAbsent(className, newLock); if (lock == null) { lock = newLock; } } return lock; } // This method is invoked by the virtual machine to load a class. private Class loadClassInternal(String name) throws ClassNotFoundException { // For backward compatibility, explicitly lock on 'this' when // the current class loader is not parallel capable. if (parallelLockMap == null) { synchronized (this) { return loadClass(name); } } else { return loadClass(name); } } // Invoked by the VM after loading class with this loader. private void checkPackageAccess(Class cls, ProtectionDomain pd) { final SecurityManager sm = System.getSecurityManager(); if (sm != null) { final String name = cls.getName(); final int i = name.lastIndexOf('.'); if (i != -1) { AccessController.doPrivileged(new PrivilegedAction() { public Void run() { sm.checkPackageAccess(name.substring(0, i)); return null; } }, new AccessControlContext(new ProtectionDomain[] {pd})); } } domains.add(pd); } /** * Finds the class with the specified binary name. * This method should be overridden by class loader implementations that * follow the delegation model for loading classes, and will be invoked by * the {@link #loadClass loadClass} method after checking the * parent class loader for the requested class. The default implementation * throws a ClassNotFoundException.

* * @param name * The binary name of the class * * @return The resulting Class object * * @throws ClassNotFoundException * If the class could not be found * * @since 1.2 */ protected Class findClass(String name) throws ClassNotFoundException { throw new ClassNotFoundException(name); } /** * Converts an array of bytes into an instance of class Class. * Before the Class can be used it must be resolved. This method * is deprecated in favor of the version that takes a binary name as its first argument, and is more secure. * * @param b * The bytes that make up the class data. The bytes in positions * off through off+len-1 should have the format * of a valid class file as defined by * The Java™ Virtual Machine Specification. * * @param off * The start offset in b of the class data * * @param len * The length of the class data * * @return The Class object that was created from the specified * class data * * @throws ClassFormatError * If the data did not contain a valid class * * @throws IndexOutOfBoundsException * If either off or len is negative, or if * off+len is greater than b.length. * * @throws SecurityException * If an attempt is made to add this class to a package that * contains classes that were signed by a different set of * certificates than this class, or if an attempt is made * to define a class in a package with a fully-qualified name * that starts with "{@code java.}". * * @see #loadClass(String, boolean) * @see #resolveClass(Class) * * @deprecated Replaced by {@link #defineClass(String, byte[], int, int) * defineClass(String, byte[], int, int)} */ @Deprecated protected final Class defineClass(byte[] b, int off, int len) throws ClassFormatError { return defineClass(null, b, off, len, null); } /** * Converts an array of bytes into an instance of class Class. * Before the Class can be used it must be resolved. * *

This method assigns a default {@link java.security.ProtectionDomain * ProtectionDomain} to the newly defined class. The * ProtectionDomain is effectively granted the same set of * permissions returned when {@link * java.security.Policy#getPermissions(java.security.CodeSource) * Policy.getPolicy().getPermissions(new CodeSource(null, null))} * is invoked. The default domain is created on the first invocation of * {@link #defineClass(String, byte[], int, int) defineClass}, * and re-used on subsequent invocations. * *

To assign a specific ProtectionDomain to the class, use * the {@link #defineClass(String, byte[], int, int, * java.security.ProtectionDomain) defineClass} method that takes a * ProtectionDomain as one of its arguments.

* * @param name * The expected binary name of the class, or * null if not known * * @param b * The bytes that make up the class data. The bytes in positions * off through off+len-1 should have the format * of a valid class file as defined by * The Java™ Virtual Machine Specification. * * @param off * The start offset in b of the class data * * @param len * The length of the class data * * @return The Class object that was created from the specified * class data. * * @throws ClassFormatError * If the data did not contain a valid class * * @throws IndexOutOfBoundsException * If either off or len is negative, or if * off+len is greater than b.length. * * @throws SecurityException * If an attempt is made to add this class to a package that * contains classes that were signed by a different set of * certificates than this class (which is unsigned), or if * name begins with "java.". * * @see #loadClass(String, boolean) * @see #resolveClass(Class) * @see java.security.CodeSource * @see java.security.SecureClassLoader * * @since 1.1 */ protected final Class defineClass(String name, byte[] b, int off, int len) throws ClassFormatError { return defineClass(name, b, off, len, null); } /* Determine protection domain, and check that: - not define java.* class, - signer of this class matches signers for the rest of the classes in package. */ private ProtectionDomain preDefineClass(String name, ProtectionDomain pd) { if (!checkName(name)) throw new NoClassDefFoundError("IllegalName: " + name); if ((name != null) && name.startsWith("java.")) { throw new SecurityException ("Prohibited package name: " + name.substring(0, name.lastIndexOf('.'))); } if (pd == null) { pd = defaultDomain; } if (name != null) checkCerts(name, pd.getCodeSource()); return pd; } private String defineClassSourceLocation(ProtectionDomain pd) { CodeSource cs = pd.getCodeSource(); String source = null; if (cs != null && cs.getLocation() != null) { source = cs.getLocation().toString(); } return source; } private Class defineTransformedClass(String name, byte[] b, int off, int len, ProtectionDomain pd, ClassFormatError cfe, String source) throws ClassFormatError { // Class format error - try to transform the bytecode and // define the class again // ClassFileTransformer[] transformers = ClassFileTransformer.getTransformers(); Class c = null; if (transformers != null) { for (ClassFileTransformer transformer : transformers) { try { // Transform byte code using transformer byte[] tb = transformer.transform(b, off, len); c = defineClass1(name, tb, 0, tb.length, pd, source); break; } catch (ClassFormatError cfe2) { // If ClassFormatError occurs, try next transformer } } } // Rethrow original ClassFormatError if unable to transform // bytecode to well-formed // if (c == null) throw cfe; return c; } private void postDefineClass(Class c, ProtectionDomain pd) { if (pd.getCodeSource() != null) { Certificate certs[] = pd.getCodeSource().getCertificates(); if (certs != null) setSigners(c, certs); } } /** * Converts an array of bytes into an instance of class Class, * with an optional ProtectionDomain. If the domain is * null, then a default domain will be assigned to the class as * specified in the documentation for {@link #defineClass(String, byte[], * int, int)}. Before the class can be used it must be resolved. * *

The first class defined in a package determines the exact set of * certificates that all subsequent classes defined in that package must * contain. The set of certificates for a class is obtained from the * {@link java.security.CodeSource CodeSource} within the * ProtectionDomain of the class. Any classes added to that * package must contain the same set of certificates or a * SecurityException will be thrown. Note that if * name is null, this check is not performed. * You should always pass in the binary name of the * class you are defining as well as the bytes. This ensures that the * class you are defining is indeed the class you think it is. * *

The specified name cannot begin with "java.", since * all classes in the "java.* packages can only be defined by the * bootstrap class loader. If name is not null, it * must be equal to the binary name of the class * specified by the byte array "b", otherwise a {@link * NoClassDefFoundError} will be thrown.

The rules about the first class defined in a package determining the * set of certificates for the package, and the restrictions on class names * are identical to those specified in the documentation for {@link * #defineClass(String, byte[], int, int, ProtectionDomain)}. * *

An invocation of this method of the form * cl.defineClass(name, * bBuffer, pd) yields exactly the same * result as the statements * *

* ... * byte[] temp = new byte[bBuffer.{@link * java.nio.ByteBuffer#remaining remaining}()]; *bBuffer.{@link java.nio.ByteBuffer#get(byte[]) * get}(temp); * return {@link #defineClass(String, byte[], int, int, ProtectionDomain) *cl.defineClass}(name, temp, 0, * temp.length,pd); *

* * @param name * The expected binary name. of the class, or * null if not known * * @param b * The bytes that make up the class data. The bytes from positions * b.position() through b.position() + b.limit() -1 * should have the format of a valid class file as defined by * The Java™ Virtual Machine Specification. * * @param protectionDomain * The ProtectionDomain of the class, or null. * * @return The Class object created from the data, * and optional ProtectionDomain. * * @throws ClassFormatError * If the data did not contain a valid class. * * @throws NoClassDefFoundError * If name is not equal to the binary * name of the class specified by b * * @throws SecurityException * If an attempt is made to add this class to a package that * contains classes that were signed by a different set of * certificates than this class, or if name begins with * "java.". * * @see #defineClass(String, byte[], int, int, ProtectionDomain) * * @since 1.5 */ protected final Class defineClass(String name, java.nio.ByteBuffer b, ProtectionDomain protectionDomain) throws ClassFormatError { int len = b.remaining(); // Use byte[] if not a direct ByteBufer: if (!b.isDirect()) { if (b.hasArray()) { return defineClass(name, b.array(), b.position() + b.arrayOffset(), len, protectionDomain); } else { // no array, or read-only array byte[] tb = new byte[len]; b.get(tb); // get bytes out of byte buffer. return defineClass(name, tb, 0, len, protectionDomain); } } protectionDomain = preDefineClass(name, protectionDomain); Class c = null; String source = defineClassSourceLocation(protectionDomain); try { c = defineClass2(name, b, b.position(), len, protectionDomain, source); } catch (ClassFormatError cfe) { byte[] tb = new byte[len]; b.get(tb); // get bytes out of byte buffer. c = defineTransformedClass(name, tb, 0, len, protectionDomain, cfe, source); } postDefineClass(c, protectionDomain); return c; } private native Class defineClass0(String name, byte[] b, int off, int len, ProtectionDomain pd); private native Class defineClass1(String name, byte[] b, int off, int len, ProtectionDomain pd, String source); private native Class defineClass2(String name, java.nio.ByteBuffer b, int off, int len, ProtectionDomain pd, String source); // true if the name is null or has the potential to be a valid binary name private boolean checkName(String name) { if ((name == null) || (name.length() == 0)) return true; if ((name.indexOf('/') != -1) || (!VM.allowArraySyntax() && (name.charAt(0) == '['))) return false; return true; } private void checkCerts(String name, CodeSource cs) { int i = name.lastIndexOf('.'); String pname = (i == -1) ? "" : name.substring(0, i); Certificate[] certs = null; if (cs != null) { certs = cs.getCertificates(); } Certificate[] pcerts = null; if (parallelLockMap == null) { synchronized (this) { pcerts = package2certs.get(pname); if (pcerts == null) { package2certs.put(pname, (certs == null? nocerts:certs)); } } } else { pcerts = ((ConcurrentHashMap)package2certs). putIfAbsent(pname, (certs == null? nocerts:certs)); } if (pcerts != null && !compareCerts(pcerts, certs)) { throw new SecurityException("class \""+ name + "\"'s signer information does not match signer information of other classes in the same package"); } } /** * check to make sure the certs for the new class (certs) are the same as * the certs for the first class inserted in the package (pcerts) */ private boolean compareCerts(Certificate[] pcerts, Certificate[] certs) { // certs can be null, indicating no certs. if ((certs == null) || (certs.length == 0)) { return pcerts.length == 0; } // the length must be the same at this point if (certs.length != pcerts.length) return false; // go through and make sure all the certs in one array // are in the other and vice-versa. boolean match; for (int i = 0; i < certs.length; i++) { match = false; for (int j = 0; j < pcerts.length; j++) { if (certs[i].equals(pcerts[j])) { match = true; break; } } if (!match) return false; } // now do the same for pcerts for (int i = 0; i < pcerts.length; i++) { match = false; for (int j = 0; j < certs.length; j++) { if (pcerts[i].equals(certs[j])) { match = true; break; } } if (!match) return false; } return true; } /** * Links the specified class. This (misleadingly named) method may be * used by a class loader to link a class. If the class c has * already been linked, then this method simply returns. Otherwise, the * class is linked as described in the "Execution" chapter of * The Java™ Language Specification. *

* * @param c * The class to link * * @throws NullPointerException * If c is null. * * @see #defineClass(String, byte[], int, int) */ protected final void resolveClass(Class c) { resolveClass0(c); } private native void resolveClass0(Class c); /** * Finds a class with the specified binary name, * loading it if necessary. * *

This method loads the class through the system class loader (see * {@link #getSystemClassLoader()}). The Class object returned * might have more than one ClassLoader associated with it. * Subclasses of ClassLoader need not usually invoke this method, * because most class loaders need to override just {@link * #findClass(String)}.

* * @param name * The binary name of the class * * @return The Class object for the specified name * * @throws ClassNotFoundException * If the class could not be found * * @see #ClassLoader(ClassLoader) * @see #getParent() */ protected final Class findSystemClass(String name) throws ClassNotFoundException { ClassLoader system = getSystemClassLoader(); if (system == null) { if (!checkName(name)) throw new ClassNotFoundException(name); Class cls = findBootstrapClass(name); if (cls == null) { throw new ClassNotFoundException(name); } return cls; } return system.loadClass(name); } /** * Returns a class loaded by the bootstrap class loader; * or return null if not found. */ private Class findBootstrapClassOrNull(String name) { if (!checkName(name)) return null; return findBootstrapClass(name); } // return null if not found private native Class findBootstrapClass(String name); /** * Returns the class with the given binary name if this * loader has been recorded by the Java virtual machine as an initiating * loader of a class with that binary name. Otherwise * null is returned.

* * @param name * The binary name of the class * * @return The Class object, or null if the class has * not been loaded * * @since 1.1 */ protected final Class findLoadedClass(String name) { if (!checkName(name)) return null; return findLoadedClass0(name); } private native final Class findLoadedClass0(String name); /** * Sets the signers of a class. This should be invoked after defining a * class.

* * @param c * The Class object * * @param signers * The signers for the class * * @since 1.1 */ protected final void setSigners(Class c, Object[] signers) { c.setSigners(signers); } // -- Resource -- /** * Finds the resource with the given name. A resource is some data * (images, audio, text, etc) that can be accessed by class code in a way * that is independent of the location of the code. * *

The name of a resource is a '/'-separated path name that * identifies the resource. * *

This method will first search the parent class loader for the * resource; if the parent is null the path of the class loader * built-in to the virtual machine is searched. That failing, this method * will invoke {@link #findResource(String)} to find the resource.

* * @param name * The resource name * * @return A URL object for reading the resource, or * null if the resource could not be found or the invoker * doesn't have adequate privileges to get the resource. * * @since 1.1 */ public URL getResource(String name) { URL url; if (parent != null) { url = parent.getResource(name); } else { url = getBootstrapResource(name); } if (url == null) { url = findResource(name); } return url; } /** * Finds all the resources with the given name. A resource is some data * (images, audio, text, etc) that can be accessed by class code in a way * that is independent of the location of the code. * *

The name of a resource is a /-separated path name that * identifies the resource. * *

The search order is described in the documentation for {@link * #getResource(String)}.

* * @param name * The resource name * * @return An enumeration of {@link java.net.URL URL} objects for * the resource. If no resources could be found, the enumeration * will be empty. Resources that the class loader doesn't have * access to will not be in the enumeration. * * @throws IOException * If I/O errors occur * * @see #findResources(String) * * @since 1.2 */ public Enumeration getResources(String name) throws IOException { Enumeration[] tmp = new Enumeration[2]; if (parent != null) { tmp[0] = parent.getResources(name); } else { tmp[0] = getBootstrapResources(name); } tmp[1] = findResources(name); return new CompoundEnumeration<>(tmp); } /** * Finds the resource with the given name. Class loader implementations * should override this method to specify where to find resources.

* * @param name * The resource name * * @return A URL object for reading the resource, or * null if the resource could not be found * * @since 1.2 */ protected URL findResource(String name) { return null; } /** * Returns an enumeration of {@link java.net.URL URL} objects * representing all the resources with the given name. Class loader * implementations should override this method to specify where to load * resources from.

* * @param name * The resource name * * @return An enumeration of {@link java.net.URL URL} objects for * the resources * * @throws IOException * If I/O errors occur * * @since 1.2 */ protected Enumeration findResources(String name) throws IOException { return java.util.Collections.emptyEnumeration(); } // index 0: java.lang.ClassLoader.class // index 1: the immediate caller of index 0. // index 2: the immediate caller of index 1. private static native Class getCaller(int index); /** * Registers the caller as parallel capable.

* The registration succeeds if and only if all of the following * conditions are met:
* 1. no instance of the caller has been created

* 2. all of the super classes (except class Object) of the caller are * registered as parallel capable

* Note that once a class loader is registered as parallel capable, there * is no way to change it back.

* * @return true if the caller is successfully registered as * parallel capable and false if otherwise. * * @since 1.7 */ protected static boolean registerAsParallelCapable() { return ParallelLoaders.register(getCaller(1)); } /** * Find a resource of the specified name from the search path used to load * classes. This method locates the resource through the system class * loader (see {@link #getSystemClassLoader()}).

* * @param name * The resource name * * @return A {@link java.net.URL URL} object for reading the * resource, or null if the resource could not be found * * @since 1.1 */ public static URL getSystemResource(String name) { ClassLoader system = getSystemClassLoader(); if (system == null) { return getBootstrapResource(name); } return system.getResource(name); } /** * Finds all resources of the specified name from the search path used to * load classes. The resources thus found are returned as an * {@link java.util.Enumeration Enumeration} of {@link * java.net.URL URL} objects. * *

The search order is described in the documentation for {@link * #getSystemResource(String)}.

* * @param name * The resource name * * @return An enumeration of resource {@link java.net.URL URL} * objects * * @throws IOException * If I/O errors occur * @since 1.2 */ public static Enumeration getSystemResources(String name) throws IOException { ClassLoader system = getSystemClassLoader(); if (system == null) { return getBootstrapResources(name); } return system.getResources(name); } /** * Find resources from the VM's built-in classloader. */ private static URL getBootstrapResource(String name) { URLClassPath ucp = getBootstrapClassPath(); Resource res = ucp.getResource(name); return res != null ? res.getURL() : null; } /** * Find resources from the VM's built-in classloader. */ private static Enumeration getBootstrapResources(String name) throws IOException { final Enumeration e = getBootstrapClassPath().getResources(name); return new Enumeration () { public URL nextElement() { return e.nextElement().getURL(); } public boolean hasMoreElements() { return e.hasMoreElements(); } }; } // Returns the URLClassPath that is used for finding system resources. static URLClassPath getBootstrapClassPath() { return sun.misc.Launcher.getBootstrapClassPath(); } /** * Returns an input stream for reading the specified resource. * *

The search order is described in the documentation for {@link * #getResource(String)}.

* * @param name * The resource name * * @return An input stream for reading the resource, or null * if the resource could not be found * * @since 1.1 */ public InputStream getResourceAsStream(String name) { URL url = getResource(name); try { return url != null ? url.openStream() : null; } catch (IOException e) { return null; } } /** * Open for reading, a resource of the specified name from the search path * used to load classes. This method locates the resource through the * system class loader (see {@link #getSystemClassLoader()}).

* * @param name * The resource name * * @return An input stream for reading the resource, or null * if the resource could not be found * * @since 1.1 */ public static InputStream getSystemResourceAsStream(String name) { URL url = getSystemResource(name); try { return url != null ? url.openStream() : null; } catch (IOException e) { return null; } } // -- Hierarchy -- /** * Returns the parent class loader for delegation. Some implementations may * use null to represent the bootstrap class loader. This method * will return null in such implementations if this class loader's * parent is the bootstrap class loader. * *

If a security manager is present, and the invoker's class loader is * not null and is not an ancestor of this class loader, then this * method invokes the security manager's {@link * SecurityManager#checkPermission(java.security.Permission) * checkPermission} method with a {@link * RuntimePermission#RuntimePermission(String) * RuntimePermission("getClassLoader")} permission to verify * access to the parent class loader is permitted. If not, a * SecurityException will be thrown.

* * @return The parent ClassLoader * * @throws SecurityException * If a security manager exists and its checkPermission * method doesn't allow access to this class loader's parent class * loader. * * @since 1.2 */ public final ClassLoader getParent() { if (parent == null) return null; SecurityManager sm = System.getSecurityManager(); if (sm != null) { ClassLoader ccl = getCallerClassLoader(); if (ccl != null && !isAncestor(ccl)) { sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION); } } return parent; } /** * Returns the system class loader for delegation. This is the default * delegation parent for new ClassLoader instances, and is * typically the class loader used to start the application. * *

This method is first invoked early in the runtime's startup * sequence, at which point it creates the system class loader and sets it * as the context class loader of the invoking Thread. * *

The default system class loader is an implementation-dependent * instance of this class. * *

If the system property "java.system.class.loader" is defined * when this method is first invoked then the value of that property is * taken to be the name of a class that will be returned as the system * class loader. The class is loaded using the default system class loader * and must define a public constructor that takes a single parameter of * type ClassLoader which is used as the delegation parent. An * instance is then created using this constructor with the default system * class loader as the parameter. The resulting class loader is defined * to be the system class loader. * *

If a security manager is present, and the invoker's class loader is * not null and the invoker's class loader is not the same as or * an ancestor of the system class loader, then this method invokes the * security manager's {@link * SecurityManager#checkPermission(java.security.Permission) * checkPermission} method with a {@link * RuntimePermission#RuntimePermission(String) * RuntimePermission("getClassLoader")} permission to verify * access to the system class loader. If not, a * SecurityException will be thrown.

* * @return The system ClassLoader for delegation, or * null if none * * @throws SecurityException * If a security manager exists and its checkPermission * method doesn't allow access to the system class loader. * * @throws IllegalStateException * If invoked recursively during the construction of the class * loader specified by the "java.system.class.loader" * property. * * @throws Error * If the system property "java.system.class.loader" * is defined but the named class could not be loaded, the * provider class does not define the required constructor, or an * exception is thrown by that constructor when it is invoked. The * underlying cause of the error can be retrieved via the * {@link Throwable#getCause()} method. * * @revised 1.4 */ public static ClassLoader getSystemClassLoader() { initSystemClassLoader(); if (scl == null) { return null; } SecurityManager sm = System.getSecurityManager(); if (sm != null) { ClassLoader ccl = getCallerClassLoader(); if (ccl != null && ccl != scl && !scl.isAncestor(ccl)) { sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION); } } return scl; } private static synchronized void initSystemClassLoader() { if (!sclSet) { if (scl != null) throw new IllegalStateException("recursive invocation"); sun.misc.Launcher l = sun.misc.Launcher.getLauncher(); if (l != null) { Throwable oops = null; scl = l.getClassLoader(); try { scl = AccessController.doPrivileged( new SystemClassLoaderAction(scl)); } catch (PrivilegedActionException pae) { oops = pae.getCause(); if (oops instanceof InvocationTargetException) { oops = oops.getCause(); } } if (oops != null) { if (oops instanceof Error) { throw (Error) oops; } else { // wrap the exception throw new Error(oops); } } } sclSet = true; } } // Returns true if the specified class loader can be found in this class // loader's delegation chain. boolean isAncestor(ClassLoader cl) { ClassLoader acl = this; do { acl = acl.parent; if (cl == acl) { return true; } } while (acl != null); return false; } // Returns the invoker's class loader, or null if none. // NOTE: This must always be invoked when there is exactly one intervening // frame from the core libraries on the stack between this method's // invocation and the desired invoker. static ClassLoader getCallerClassLoader() { // NOTE use of more generic Reflection.getCallerClass() Class caller = Reflection.getCallerClass(3); // This can be null if the VM is requesting it if (caller == null) { return null; } // Circumvent security check since this is package-private return caller.getClassLoader0(); } // The class loader for the system // @GuardedBy("ClassLoader.class") private static ClassLoader scl; // Set to true once the system class loader has been set // @GuardedBy("ClassLoader.class") private static boolean sclSet; // -- Package -- /** * Defines a package by name in this ClassLoader. This allows * class loaders to define the packages for their classes. Packages must * be created before the class is defined, and package names must be * unique within a class loader and cannot be redefined or changed once * created.

* * @param name * The package name * * @param specTitle * The specification title * * @param specVersion * The specification version * * @param specVendor * The specification vendor * * @param implTitle * The implementation title * * @param implVersion * The implementation version * * @param implVendor * The implementation vendor * * @param sealBase * If not null, then this package is sealed with * respect to the given code source {@link java.net.URL * URL} object. Otherwise, the package is not sealed. * * @return The newly defined Package object * * @throws IllegalArgumentException * If package name duplicates an existing package either in this * class loader or one of its ancestors * * @since 1.2 */ protected Package definePackage(String name, String specTitle, String specVersion, String specVendor, String implTitle, String implVersion, String implVendor, URL sealBase) throws IllegalArgumentException { synchronized (packages) { Package pkg = getPackage(name); if (pkg != null) { throw new IllegalArgumentException(name); } pkg = new Package(name, specTitle, specVersion, specVendor, implTitle, implVersion, implVendor, sealBase, this); packages.put(name, pkg); return pkg; } } /** * Returns a Package that has been defined by this class loader * or any of its ancestors.

* * @param name * The package name * * @return The Package corresponding to the given name, or * null if not found * * @since 1.2 */ protected Package getPackage(String name) { Package pkg; synchronized (packages) { pkg = packages.get(name); } if (pkg == null) { if (parent != null) { pkg = parent.getPackage(name); } else { pkg = Package.getSystemPackage(name); } if (pkg != null) { synchronized (packages) { Package pkg2 = packages.get(name); if (pkg2 == null) { packages.put(name, pkg); } else { pkg = pkg2; } } } } return pkg; } /** * Returns all of the Packages defined by this class loader and * its ancestors.

* * @return The array of Package objects defined by this * ClassLoader * * @since 1.2 */ protected Package[] getPackages() { Map map; synchronized (packages) { map = new HashMap<>(packages); } Package[] pkgs; if (parent != null) { pkgs = parent.getPackages(); } else { pkgs = Package.getSystemPackages(); } if (pkgs != null) { for (int i = 0; i < pkgs.length; i++) { String pkgName = pkgs[i].getName(); if (map.get(pkgName) == null) { map.put(pkgName, pkgs[i]); } } } return map.values().toArray(new Package[map.size()]); } // -- Native library access -- /** * Returns the absolute path name of a native library. The VM invokes this * method to locate the native libraries that belong to classes loaded with * this class loader. If this method returns null, the VM * searches the library along the path specified as the * "java.library.path" property.

* * @param libname * The library name * * @return The absolute path of the native library * * @see System#loadLibrary(String) * @see System#mapLibraryName(String) * * @since 1.2 */ protected String findLibrary(String libname) { return null; } /** * The inner class NativeLibrary denotes a loaded native library instance. * Every classloader contains a vector of loaded native libraries in the * private field nativeLibraries. The native libraries loaded * into the system are entered into the systemNativeLibraries * vector. * *

Every native library requires a particular version of JNI. This is * denoted by the private jniVersion field. This field is set by * the VM when it loads the library, and used by the VM to pass the correct * version of JNI to the native methods.

* * @see ClassLoader * @since 1.2 */ static class NativeLibrary { // opaque handle to native library, used in native code. long handle; // the version of JNI environment the native library requires. private int jniVersion; // the class from which the library is loaded, also indicates // the loader this native library belongs. private Class fromClass; // the canonicalized name of the native library. String name; native void load(String name); native long find(String name); native void unload(); public NativeLibrary(Class fromClass, String name) { this.name = name; this.fromClass = fromClass; } protected void finalize() { synchronized (loadedLibraryNames) { if (fromClass.getClassLoader() != null && handle != 0) { /* remove the native library name */ int size = loadedLibraryNames.size(); for (int i = 0; i < size; i++) { if (name.equals(loadedLibraryNames.elementAt(i))) { loadedLibraryNames.removeElementAt(i); break; } } /* unload the library. */ ClassLoader.nativeLibraryContext.push(this); try { unload(); } finally { ClassLoader.nativeLibraryContext.pop(); } } } } // Invoked in the VM to determine the context class in // JNI_Load/JNI_Unload static Class getFromClass() { return ClassLoader.nativeLibraryContext.peek().fromClass; } } // All native library names we've loaded. private static Vector loadedLibraryNames = new Vector<>(); // Native libraries belonging to system classes. private static Vector systemNativeLibraries = new Vector<>(); // Native libraries associated with the class loader. private Vector nativeLibraries = new Vector<>(); // native libraries being loaded/unloaded. private static Stack nativeLibraryContext = new Stack<>(); // The paths searched for libraries private static String usr_paths[]; private static String sys_paths[]; private static String[] initializePath(String propname) { String ldpath = System.getProperty(propname, ""); String ps = File.pathSeparator; int ldlen = ldpath.length(); int i, j, n; // Count the separators in the path i = ldpath.indexOf(ps); n = 0; while (i >= 0) { n++; i = ldpath.indexOf(ps, i + 1); } // allocate the array of paths - n :'s = n + 1 path elements String[] paths = new String[n + 1]; // Fill the array with paths from the ldpath n = i = 0; j = ldpath.indexOf(ps); while (j >= 0) { if (j - i > 0) { paths[n++] = ldpath.substring(i, j); } else if (j - i == 0) { paths[n++] = "."; } i = j + 1; j = ldpath.indexOf(ps, i); } paths[n] = ldpath.substring(i, ldlen); return paths; } // Invoked in the java.lang.Runtime class to implement load and loadLibrary. static void loadLibrary(Class fromClass, String name, boolean isAbsolute) { ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader(); if (sys_paths == null) { usr_paths = initializePath("java.library.path"); sys_paths = initializePath("sun.boot.library.path"); } if (isAbsolute) { if (loadLibrary0(fromClass, new File(name))) { return; } throw new UnsatisfiedLinkError("Can't load library: " + name); } if (loader != null) { String libfilename = loader.findLibrary(name); if (libfilename != null) { File libfile = new File(libfilename); if (!libfile.isAbsolute()) { throw new UnsatisfiedLinkError( "ClassLoader.findLibrary failed to return an absolute path: " + libfilename); } if (loadLibrary0(fromClass, libfile)) { return; } throw new UnsatisfiedLinkError("Can't load " + libfilename); } } for (int i = 0 ; i < sys_paths.length ; i++) { File libfile = new File(sys_paths[i], System.mapLibraryName(name)); if (loadLibrary0(fromClass, libfile)) { return; } } if (loader != null) { for (int i = 0 ; i < usr_paths.length ; i++) { File libfile = new File(usr_paths[i], System.mapLibraryName(name)); if (loadLibrary0(fromClass, libfile)) { return; } } } // Oops, it failed throw new UnsatisfiedLinkError("no " + name + " in java.library.path"); } private static boolean loadLibrary0(Class fromClass, final File file) { boolean exists = AccessController.doPrivileged( new PrivilegedAction