1 /*
   2  * Copyright (c) 1996, 2013, 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 
  26 package java.beans;
  27 
  28 import java.lang.ref.Reference;
  29 import java.lang.ref.WeakReference;
  30 import java.lang.reflect.Method;
  31 import java.util.List;
  32 import java.util.ArrayList;
  33 
  34 /**
  35  * A MethodDescriptor describes a particular method that a Java Bean
  36  * supports for external access from other components.
  37  *
  38  * @since 1.1
  39  */
  40 
  41 public class MethodDescriptor extends FeatureDescriptor {
  42 
  43     private final MethodRef methodRef = new MethodRef();
  44 
  45     private String[] paramNames;
  46 
  47     private List<WeakReference<Class<?>>> params;
  48 
  49     private ParameterDescriptor parameterDescriptors[];
  50 
  51     /**
  52      * Constructs a <code>MethodDescriptor</code> from a
  53      * <code>Method</code>.
  54      *
  55      * @param method    The low-level method information.
  56      */
  57     public MethodDescriptor(Method method) {
  58         this(method, null);
  59     }
  60 
  61 
  62     /**
  63      * Constructs a <code>MethodDescriptor</code> from a
  64      * <code>Method</code> providing descriptive information for each
  65      * of the method's parameters.
  66      *
  67      * @param method    The low-level method information.
  68      * @param parameterDescriptors  Descriptive information for each of the
  69      *                          method's parameters.
  70      */
  71     public MethodDescriptor(Method method,
  72                 ParameterDescriptor parameterDescriptors[]) {
  73         setName(method.getName());
  74         setMethod(method);
  75         this.parameterDescriptors = (parameterDescriptors != null)
  76                 ? parameterDescriptors.clone()
  77                 : null;
  78     }
  79 
  80     /**
  81      * Gets the method that this MethodDescriptor encapsulates.
  82      *
  83      * @return The low-level description of the method
  84      */
  85     public synchronized Method getMethod() {
  86         Method method = this.methodRef.get();
  87         if (method == null) {
  88             Class<?> cls = getClass0();
  89             String name = getName();
  90             if ((cls != null) && (name != null)) {
  91                 Class<?>[] params = getParams();
  92                 if (params == null) {
  93                     for (int i = 0; i < 3; i++) {
  94                         // Find methods for up to 2 params. We are guessing here.
  95                         // This block should never execute unless the classloader
  96                         // that loaded the argument classes disappears.
  97                         method = Introspector.findMethod(cls, name, i, null);
  98                         if (method != null) {
  99                             break;
 100                         }
 101                     }
 102                 } else {
 103                     method = Introspector.findMethod(cls, name, params.length, params);
 104                 }
 105                 setMethod(method);
 106             }
 107         }
 108         return method;
 109     }
 110 
 111     private synchronized void setMethod(Method method) {
 112         if (method == null) {
 113             return;
 114         }
 115         if (getClass0() == null) {
 116             setClass0(method.getDeclaringClass());
 117         }
 118         setParams(getParameterTypes(getClass0(), method));
 119         this.methodRef.set(method);
 120     }
 121 
 122     private synchronized void setParams(Class<?>[] param) {
 123         if (param == null) {
 124             return;
 125         }
 126         paramNames = new String[param.length];
 127         params = new ArrayList<>(param.length);
 128         for (int i = 0; i < param.length; i++) {
 129             paramNames[i] = param[i].getName();
 130             params.add(new WeakReference<Class<?>>(param[i]));
 131         }
 132     }
 133 
 134     // pp getParamNames used as an optimization to avoid method.getParameterTypes.
 135     String[] getParamNames() {
 136         return paramNames;
 137     }
 138 
 139     private synchronized Class<?>[] getParams() {
 140         Class<?>[] clss = new Class<?>[params.size()];
 141 
 142         for (int i = 0; i < params.size(); i++) {
 143             Reference<? extends Class<?>> ref = (Reference<? extends Class<?>>)params.get(i);
 144             Class<?> cls = ref.get();
 145             if (cls == null) {
 146                 return null;
 147             } else {
 148                 clss[i] = cls;
 149             }
 150         }
 151         return clss;
 152     }
 153 
 154     /**
 155      * Gets the ParameterDescriptor for each of this MethodDescriptor's
 156      * method's parameters.
 157      *
 158      * @return The locale-independent names of the parameters.  May return
 159      *          a null array if the parameter names aren't known.
 160      */
 161     public ParameterDescriptor[] getParameterDescriptors() {
 162         return (this.parameterDescriptors != null)
 163                 ? this.parameterDescriptors.clone()
 164                 : null;
 165     }
 166 
 167     private static Method resolve(Method oldMethod, Method newMethod) {
 168         if (oldMethod == null) {
 169             return newMethod;
 170         }
 171         if (newMethod == null) {
 172             return oldMethod;
 173         }
 174         return !oldMethod.isSynthetic() && newMethod.isSynthetic() ? oldMethod : newMethod;
 175     }
 176 
 177     /*
 178      * Package-private constructor
 179      * Merge two method descriptors.  Where they conflict, give the
 180      * second argument (y) priority over the first argument (x).
 181      * @param x  The first (lower priority) MethodDescriptor
 182      * @param y  The second (higher priority) MethodDescriptor
 183      */
 184 
 185     MethodDescriptor(MethodDescriptor x, MethodDescriptor y) {
 186         super(x, y);
 187 
 188         this.methodRef.set(resolve(x.methodRef.get(), y.methodRef.get()));
 189         params = x.params;
 190         if (y.params != null) {
 191             params = y.params;
 192         }
 193         paramNames = x.paramNames;
 194         if (y.paramNames != null) {
 195             paramNames = y.paramNames;
 196         }
 197 
 198         parameterDescriptors = x.parameterDescriptors;
 199         if (y.parameterDescriptors != null) {
 200             parameterDescriptors = y.parameterDescriptors;
 201         }
 202     }
 203 
 204     /*
 205      * Package-private dup constructor
 206      * This must isolate the new object from any changes to the old object.
 207      */
 208     MethodDescriptor(MethodDescriptor old) {
 209         super(old);
 210 
 211         this.methodRef.set(old.getMethod());
 212         params = old.params;
 213         paramNames = old.paramNames;
 214 
 215         if (old.parameterDescriptors != null) {
 216             int len = old.parameterDescriptors.length;
 217             parameterDescriptors = new ParameterDescriptor[len];
 218             for (int i = 0; i < len ; i++) {
 219                 parameterDescriptors[i] = new ParameterDescriptor(old.parameterDescriptors[i]);
 220             }
 221         }
 222     }
 223 
 224     void appendTo(StringBuilder sb) {
 225         appendTo(sb, "method", this.methodRef.get());
 226         if (this.parameterDescriptors != null) {
 227             sb.append("; parameterDescriptors={");
 228             for (ParameterDescriptor pd : this.parameterDescriptors) {
 229                 sb.append(pd).append(", ");
 230             }
 231             sb.setLength(sb.length() - 2);
 232             sb.append("}");
 233         }
 234     }
 235 }