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jeremybenn |
/* RemoteObjectInvocationHandler.java -- RMI stub replacement.
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Copyright (C) 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.rmi.server;
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import gnu.java.rmi.server.RMIHashes;
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import java.io.Serializable;
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import java.lang.reflect.InvocationHandler;
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import java.lang.reflect.Method;
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import java.lang.reflect.Proxy;
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import java.rmi.Remote;
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import java.rmi.RemoteException;
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import java.rmi.UnexpectedException;
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import java.rmi.registry.Registry;
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import java.rmi.server.RemoteObject;
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import java.rmi.server.RemoteRef;
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import java.rmi.server.UnicastRemoteObject;
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import java.util.Hashtable;
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/**
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* Together with dynamic proxy instance, this class replaces the generated RMI
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* stub (*_Stub) classes that (following 1.5 specification) should be no longer
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* required. It is unusual to use the instances of this class directly in the
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* user program. Such instances are automatically created and returned by
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* {@link Registry} or {@link UnicastRemoteObject} methods if the remote
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* reference is known but the corresponding stub class is not accessible.
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*
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* @see Registry#lookup
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*
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* @author Audrius Meskauskas (AudriusA@Bioinformatics.org)
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*/
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public class RemoteObjectInvocationHandler extends RemoteObject implements
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InvocationHandler, Remote, Serializable
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{
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/**
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* Use the jdk 1.5 SUID for interoperability.
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*/
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static final long serialVersionUID = 2L;
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/**
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* The RMI method hash codes, computed once as described in the section 8.3
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* of the Java Remote Method Invocation (RMI) Specification.
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*/
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static Hashtable methodHashCodes = new Hashtable();
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/**
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* The empty class array to define parameters of .hashCode and .toString.
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*/
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static final Class[] noArgsC = new Class[0];
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/**
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* The class array to define parameters of .equals
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*/
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static final Class[] anObjectC = new Class[] { Object.class };
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/**
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* The empty object array to replace null when no args are passed.
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*/
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static final Object[] noArgs = new Object[0];
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/**
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* Construct the remote invocation handler that forwards calls to the given
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* remote object.
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*
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* @param reference the reference to the remote object where the method
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* calls should be forwarded.
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*/
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public RemoteObjectInvocationHandler(RemoteRef reference)
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{
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super(reference);
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}
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/**
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* Invoke the remote method. When the known method is invoked on a created RMI
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* stub proxy class, the call is delivered to this method and then transferred
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* to the {@link RemoteRef#invoke(Remote, Method, Object[], long)} of the
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* remote reference that was passed in constructor. The methods are handled as
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* following:
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* <ul>
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* <li> The toString() method is delegated to the passed proxy instance.</li>
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* <li>The .equals method only returns true if the passed object is an
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* instance of proxy class and its invocation handler is equal to this
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* invocation handles.</li>
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* <li>The .hashCode returns the hashCode of this invocation handler (if the.</li>
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* <li>All other methods are converted to remote calls and forwarded to the
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* remote reference. </li>
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* </ul>
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*
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* @param proxyInstance
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* the instance of the proxy stub
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* @param method
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* the method being invoked
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* @param parameters
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* the method parameters
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* @return the method return value, returned by RemoteRef.invoke
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* @throws IllegalAccessException
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* if the passed proxy instance does not implement Remote interface.
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* @throws UnexpectedException
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* if remote call throws some exception, not listed in the
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* <code>throws</code> clause of the method being called.
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* @throws Throwable
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* that is thrown by remote call, if that exception is listend in
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* the <code>throws</code> clause of the method being called.
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*/
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public Object invoke(Object proxyInstance, Method method, Object[] parameters)
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throws Throwable
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{
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if (!(proxyInstance instanceof Remote))
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{
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String name = proxyInstance == null ? "null"
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: proxyInstance.getClass().getName();
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throw new IllegalAccessException(name + " does not implement "
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+ Remote.class.getName());
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}
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if (parameters == null)
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parameters = noArgs;
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String name = method.getName();
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switch (name.charAt(0))
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{
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case 'e':
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if (parameters.length == 1 && name.equals("equals")
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&& method.getParameterTypes()[0].equals(Object.class))
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{
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if (parameters[0] instanceof Proxy)
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{
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Object handler = Proxy.getInvocationHandler(parameters[0]);
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if (handler == null)
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return Boolean.FALSE;
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else
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return handler.equals(this) ? Boolean.TRUE : Boolean.FALSE;
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}
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else
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return Boolean.FALSE;
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}
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break;
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case 'h':
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if (parameters.length == 0 && name.equals("hashCode"))
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{
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int hashC = Proxy.getInvocationHandler(proxyInstance).hashCode();
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return new Integer(hashC);
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}
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break;
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case 't':
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if (parameters.length == 0 && name.equals("toString"))
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return "Proxy stub:"+ref.remoteToString();
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break;
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default:
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break;
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}
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Long hash = (Long) methodHashCodes.get(method);
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if (hash == null)
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{
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hash = new Long(RMIHashes.getMethodHash(method));
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methodHashCodes.put(method, hash);
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}
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try
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{
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return getRef().invoke((Remote) proxyInstance, method, parameters,
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hash.longValue());
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}
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catch (RuntimeException exception)
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{
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// RuntimeException is always supported.
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throw exception;
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}
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catch (RemoteException exception)
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{
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// All remote methods can throw RemoteException.
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throw exception;
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}
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catch (Error exception)
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{
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throw exception;
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}
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catch (Exception exception)
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{
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Class[] exceptions = method.getExceptionTypes();
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Class exceptionClass = exception.getClass();
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for (int i = 0; i < exceptions.length; i++)
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{
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if (exceptions[i].equals(exceptionClass))
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throw exception;
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}
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throw new UnexpectedException(method.getName(), exception);
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}
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}
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}
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