LocalStaticRedirector.java

/*
** Module   : LocalStaticRedirector.java
** Abstract : used by a proxy to call methods that "implement" an interface
**
** Copyright (c) 2011-2017, Golden Code Development Corporation.
**
** -#- -I- --Date-- -----------------------Description------------------------
** 001 GES 20111018 Moved static code here from LocalRedirector.
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
** 
** Additional terms under GNU Affero GPL version 3 section 7:
** 
**   Under Section 7 of the GNU Affero GPL version 3, the following additional
**   terms apply to the works covered under the License.  These additional terms
**   are non-permissive additional terms allowed under Section 7 of the GNU
**   Affero GPL version 3 and may not be removed by you.
** 
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** 
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**     work or Appropriate Legal Notices displayed by works containing the covered
**     work.  You may not remove from the covered work any author or developer
**     credit already included within the covered work.
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** 
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*/
                              
package com.goldencode.p2j.net;


import java.lang.reflect.*;
import java.io.*;
import java.util.*;
import com.goldencode.p2j.util.*;


/**
 * Provides the proxy handler for a local object which redirects interface
 * methods to static target methods. The purpose is to allow code written
 * normally for remote access to be linked together "locally" (within the same
 * JVM).
 * <p>
 * Optionally, a {@link LocalStateSync} instance can be provided. If provided,
 * it will be used to maintain the {@link StateSynchronizer} semantics which
 * is missing in local redirector environments which have no {@link Session}
 * object which would otherwise service that requirement.
 */
public class LocalStaticRedirector
extends InvocationStub
{
   /** Target methods mapped by interface methods. */
   private Map<Method, Method> map = new HashMap<Method, Method>();
   
   /** Utility for local state synchronization. */
   private LocalStateSync state = null;
   
   /**
    * Creates a unique instance of an object that can handle invocations 
    * of any proxied interface method by redirecting the method calls to
    * static methods in a local class that match the interface method
    * signatures.  Any return value and/or exceptions thrown will be handled
    * as needed.
    * <p>
    * No state synchronization will be performed.
    *
    * @param    map
    *           The map of interface methods to their static method
    *           equivalents.  Must not be <code>null</code>.
    */      
   public LocalStaticRedirector(Map<Method, Method> map)
   {
      this.map = map;
   }
   
   /**
    * Creates a unique instance of an object that can handle invocations 
    * of any proxied interface method by redirecting the method calls to
    * static methods in a local class that match the interface method
    * signatures.  Any return value and/or exceptions thrown will be handled
    * as needed.
    *
    * @param    map
    *           The map of interface methods to their static method
    *           equivalents.  Must not be <code>null</code>.
    * @param    state
    *           The state synchronizer on which to get and apply changes
    *           before invoking the method call.
    */      
   public LocalStaticRedirector(Map<Method, Method> map,
                                LocalStateSync      state)
   {
      this(map);
      this.state = state;
   }
   
   /**
    * This method acts as an interceptor which is called every time a
    * method of the proxy object is invoked.
    * <p>
    * If a state synchronizer instance has been provided, the call to
    * {@link LocalStateSync#sync} will be implemented before the proxied
    * method is invoked.
    *
    * @param    proxy
    *           Proxy object upon which the intercepted method is invoked.
    * @param    method
    *           Method to be invoked through reflection.
    * @param    args
    *           Arguments, if any, to <code>method</code>.
    *
    * @return   Result of the mapped call.
    *
    * @throws   Throwable
    *           if an exception/error occurs upon the invocation target,
    *           or if any problem occurs during pre- or post-processing.
    */
   public Object invokeCore(Object proxy, Method method, Object[] args)
   throws Throwable
   {
      Method target = map.get(method);

      if (target == null)
      {
         throw new SilentUnwindException();
      }
      
      if (state != null)
      {
         state.sync();
      }
      
      return target.invoke(null, args);
   }
}