InvocationHandler


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4   * by the @authors tag. See the copyright.txt in the distribution for a
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8   * under the terms of the GNU Lesser General Public License as
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10  * the License, or (at your option) any later version.
11  *
12  * This software is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with this software; if not, write to the Free
19  * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20  * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21  */
22  package org.jboss.proxy.compiler;
23  
24  import java.lang.reflect.Method  ;
25  
26  /**
27   * An invoker is a target of method calls, where the calls are expressed
28   * not as primitive Java method invocations, but according to the conventions
29   * of the Core Reflection API.
30   * Invokers are designed to be used along with the Core Reflection API.
31   * <p>
32   * The Invoker.invoke operation is similar to java.lang.reflect.Method.invoke,
33   * except that the object (or objects) which receives the message is hidden
34   * behind the invoker.  Also, unlike Method.invoke, the action of the
35   * Invoker.invoke operation is completely under programmer control,
36   * because Invoker.invoke is an interface method, not a native method.
37   * <p>
38   * You can wrap an invoker around an object so that the invoker passes
39   * all method calls down to the object.  Such an invoker is called a
40   * <em>proxy invoker</em> for that object.
41   * <p>
42   * You can also wrap a new object around an invoker, so that the object
43   * implements some given interface (or interfaces), and passes all method
44   * calls up to the invoker.
45   * Such an object is called a <em>proxy target object</em> for that invoker.
46   * <p>
47   * You can do more complex tasks with invokers, such as passing each method
48   * call through a network connection before it reaches its target object.
49   * You can also filter or replicate method invocations.  You can even
50   * execute the the invocations interpretively, without ever calling
51   * the method on a "real" Java object.
52   *
53   * @see Method#invoke
54   * @see Invoker#invoke
55   * @see Proxies#newInvoker
56   * @see Proxies#newTarget
57   *
58   * @author Unknown
59   * @version $Revision: 37459 $
60   */
61  public interface InvocationHandler
62  {
63     /**
64      * Processes a method invocation on a proxy instance and returns the
65      * result.
66      *
67      * @param dummy     ???
68      * @param method    The method instance corresponding to the interface
69      *                  method invoked on the proxy instance.
70      * @param args      An array of objects containing the values of the
71      *                  arguments passed in the method invocation on the proxy
72      *                  instance, or null if interface method takes no
73      *                  arguments.
74      * @return          The value to return from the method invocation on
75      *                  the proxy instance. 
76      *
77      * @throws Throwable    The exception to throw from the method invocation
78      *                      on the proxy instance.
79      */
80     Object   invoke(Object   dummy, Method   method, Object  [] args)
81        throws Throwable  ;
82  }
83
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