DelegatingInvocationHandler


1   /*
2    * All content copyright (c) 2003-2006 Terracotta, Inc., except as may otherwise be noted in a separate copyright notice.  All rights reserved.
3    */
4   package com.tc.common.proxy;
5   
6   import com.tc.logging.TCLogger;
7   import com.tc.logging.TCLogging;
8   import com.tc.util.Assert;
9   
10  import java.lang.reflect.InvocationTargetException  ;
11  import java.lang.reflect.Method  ;
12  
13  /**
14   * @author andrew A {@link GenericInvocationHandler}that delegates all unknown methods to a special 'delegate' object.
15   *         This is very useful for creating delegates that override only certain methods.
16   */
17  class DelegatingInvocationHandler extends GenericInvocationHandler {
18    private static final TCLogger logger = TCLogging.getLogger(GenericInvocationHandler.class);
19    private final Object            delegate;
20  
21    public DelegatingInvocationHandler(Object   delegate, Object   handler) {
22      super(handler);
23      Assert.eval(delegate != null);
24      this.delegate = delegate;
25    }
26  
27    protected Object   handlerMethodNotFound(Object   proxy, Method   method, Object  [] args) throws Throwable   {
28      try {
29        Method   theMethod = delegate.getClass().getMethod(method.getName(), method.getParameterTypes());
30  
31        try {
32          theMethod.setAccessible(true);
33        } catch (SecurityException   se) {
34          logger.warn("Cannot setAccessible(true) for method [" + theMethod + "], " + se.getMessage());
35        }
36  
37        return theMethod.invoke(delegate, args);
38      } catch (InvocationTargetException   ite) {
39        // We need to unwrap this; we want to throw what the method actually
40        // threw, not an InvocationTargetException (which causes all sorts of
41        // madness, since it's unlikely the interface method throws that
42        // exception, and you'll end up with an UndeclaredThrowableException.
43        // Blech.)
44        throw ite.getCause();
45      } catch (NoSuchMethodException   nsme) {
46        return super.handlerMethodNotFound(proxy, method, args);
47      }
48    }
49  }
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