Bug 279649 - Dynamically create Java proxies. r=darin.

This file was copied in CVS from the following location:
mozilla/extensions/java/xpcom/XPCOMJavaProxy.java
Original committer: pedemont%us.ibm.com
Original revision: 1.1
Original date: 2005/02/23 20:19:55

extensions/java/xpcom/src/org/mozilla/xpcom/internal/XPCOMJavaProxy.java

@@ -0,0 +1,230 @@
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Java XPCOM Bindings.
+ *
+ * The Initial Developer of the Original Code is
+ * IBM Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 2004
+ * IBM Corporation. All Rights Reserved.
+ *
+ * Contributor(s):
+ *   Javier Pedemonte (jhpedemonte@gmail.com)
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+package org.mozilla.xpcom;
+
+import java.lang.reflect.*;
+
+
+/**
+ * This class is used to pass XPCOM objects to Java functions.  A
+ * <code>java.lang.reflect.Proxy</code> instance is created using the expected
+ * interface, and all calls to the proxy are forwarded to the XPCOM object.
+ */
+public final class XPCOMJavaProxy implements InvocationHandler {
+
+  /**
+   * Pointer to the XPCOM object for which we are a proxy.
+   */
+  protected long nativeXPCOMPtr;
+
+  /**
+   * Default constructor.
+   *
+   * @param aXPCOMInstance  address of XPCOM object as a long
+   */
+  public XPCOMJavaProxy(long aXPCOMInstance)
+  {
+    nativeXPCOMPtr = aXPCOMInstance;
+  }
+
+  /**
+   * Creates a Proxy for the given XPCOM object.
+   *
+   * @param aInterface      interface from which to create Proxy
+   * @param aXPCOMInstance  address of XPCOM object as a long
+   *
+   * @return  Proxy of given XPCOM object
+   */
+  protected static Object createProxy(Class aInterface, long aXPCOMInstance)
+  {
+    return Proxy.newProxyInstance(aInterface.getClassLoader(),
+                                  new Class[] { aInterface,
+                                                XPCOMJavaProxyBase.class },
+                                  new XPCOMJavaProxy(aXPCOMInstance));
+  }
+
+  /**
+   * All calls to the Java proxy are forwarded to this method.  This method
+   * takes care of a few of the <code>Object</code> method calls;  all other
+   * calls are forwarded to the XPCOM object.
+   *
+   * @param aProxy    Proxy created by <code>createProxy</code>
+   * @param aMethod   object that describes the called method
+   * @param aParams   array of the arguments passed to the method
+   *
+   * @return  return value as defined by given <code>aMethod</code>
+   */
+  public Object invoke(Object aProxy, Method aMethod, Object[] aParams)
+    throws Throwable
+  {
+    String methodName = aMethod.getName();
+
+    // Handle the three java.lang.Object methods that are passed to us.
+    if (aMethod.getDeclaringClass() == Object.class)  {
+      if (methodName.equals("hashCode"))  {
+        return proxyHashCode(aProxy);
+      }
+      if (methodName.equals("equals")) {
+        return proxyEquals(aProxy, aParams[0]);
+      }
+      if (methodName.equals("toString")) {
+        return proxyToString(aProxy);
+      }
+      System.err.println("WARNING: Unhandled Object method [" +
+                         methodName + "]");
+      return null;
+    }
+
+    // Handle the 'finalize' method called during garbage collection
+    if (aMethod.getDeclaringClass() == XPCOMJavaProxyBase.class) {
+      if (methodName.equals("finalize")) {
+        finalizeProxy(aProxy);
+      } else {
+        System.err.println("WARNING: Unhandled XPCOMJavaProxyBase method [" +
+                           methodName + "]");
+      }
+      return null;
+    }
+
+    // If not already handled, pass method calls to XPCOM object.
+    return callXPCOMMethod(aProxy, methodName, aParams);
+  }
+
+  /**
+   * Handles method calls of <code>java.lang.Object.hashCode</code>
+   *
+   * @param aProxy  Proxy created by <code>createProxy</code>
+   *
+   * @return  Integer object representing hash code of given object
+   *
+   * @see Object#hashCode()
+   */
+  protected static Integer proxyHashCode(Object aProxy)
+  {
+    return new Integer(System.identityHashCode(aProxy));
+  }
+
+  /**
+   * Handles method calls of <code>java.lang.Object.equals</code>
+   *
+   * @param aProxy  Proxy created by <code>createProxy</code>
+   * @param aOther  another object
+   *
+   * @return  <code>true</code> if the given objects are the same;
+   *          <code>false</code> otherwise
+   *
+   * @see Object#equals(Object)
+   */
+  protected static Boolean proxyEquals(Object aProxy, Object aOther)
+  {
+    return (aProxy == aOther ? Boolean.TRUE : Boolean.FALSE);
+  }
+
+  /**
+   * Handles method calls of <code>java.lang.Object.toString</code>
+   *
+   * @param aProxy  Proxy created by <code>createProxy</code>
+   *
+   * @return  String representation of given object
+   *
+   * @see Object#toString()
+   */
+  protected static String proxyToString(Object aProxy)
+  {
+    return aProxy.getClass().getInterfaces()[0].getName() + '@' +
+           Integer.toHexString(aProxy.hashCode());
+  }
+
+  /**
+   * Indicates whether the given object is an XPCOMJavaProxy.
+   *
+   * @param aObject  object to check
+   *
+   * @return  <code>true</code> if the given object is an XPCOMJavaProxy;
+   *          <code>false</code> otherwise
+   */
+  protected static boolean isXPCOMJavaProxy(Object aObject)
+  {
+    Class objectClass = aObject.getClass();
+    if (Proxy.isProxyClass(objectClass)) {
+      Class[] interfaces = objectClass.getInterfaces();
+      if (interfaces[interfaces.length-1] == XPCOMJavaProxyBase.class) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /**
+   * Returns the XPCOM object that the given proxy references.
+   *
+   * @param aProxy  Proxy created by <code>createProxy</code>
+   *
+   * @return  address of XPCOM object as a long
+   */
+  protected static long getNativeXPCOMInstance(Object aProxy)
+  {
+    XPCOMJavaProxy proxy = (XPCOMJavaProxy) Proxy.getInvocationHandler(aProxy);
+    return proxy.nativeXPCOMPtr;
+  }
+
+  /**
+   * Calls the XPCOM object referenced by the proxy with the given method.
+   *
+   * @param aProxy        Proxy created by <code>createProxy</code>
+   * @param aMethodName   name of method that we want to call
+   * @param aParams       array of params passed to method
+   *
+   * @return  return value as defined by given method
+   *
+   * @exception XPCOMException if XPCOM method failed.  Values of XPCOMException
+   *            are defined by the method called.
+   */
+  protected static native
+   Object callXPCOMMethod(Object aProxy, String aMethodName, Object[] aParams);
+
+  /**
+   * Called when the proxy is garbage collected by the JVM.  Allows us to clean
+   * up any references to the XPCOM object.
+   *
+   * @param aProxy  reference to Proxy that is being garbage collected
+   */
+  protected static native
+   void finalizeProxy(Object aProxy);
+
+}