# LocalRedirector.java

    /*
    ** Module   : LocalRedirector.java
    ** Abstract : used by a proxy to call methods on a local instance
    **
    ** Copyright (c) 2011-2017, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- -----------------------Description------------------------
    ** 001 GES 20111012 First version.
    ** 002 GES 20111018 This is now the redirector for instance methods. Static
    **                  support was moved to LocalStaticRedirector. Added support
    **                  for a state synchronizer.
    */
    /*
    ** 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.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     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.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
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    **
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    **
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    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    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 target instance 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 LocalRedirector
    extends InvocationStub
    {
       /** Target methods. */
       private Set<Method> methods = null;

       /** Instance on which to invoke methods. <code>null</code> for statics. */
       private Object instance = null;

       /** 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
        * instance 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    instance
        *           The instance upon which to target the method invocations. Use
        *           <code>null</code> if the methods are static.
        * @param    methods
        *           The set of target interface methods. Must not be
        *           <code>null</code>.
        */
       public LocalRedirector(Object instance, Set<Method> methods)
       {
          this.instance = instance;
          this.methods  = methods;
       }

       /**
        * Creates a unique instance of an object that can handle invocations
        * of any proxied interface method by redirecting the method calls to
        * instance methods in a local class that match the interface method
        * signatures.  Any return value and/or exceptions thrown will be handled
        * as needed.
        *
        * @param    instance
        *           The instance upon which to target the method invocations. Use
        *           <code>null</code> if the methods are static.
        * @param    methods
        *           The set of target interface methods. Must not be
        *           <code>null</code>.
        * @param    state
        *           The state synchronizer on which to get and apply changes
        *           before invoking the method call.
        */
       public LocalRedirector(Object         instance,
                              Set<Method>    methods,
                              LocalStateSync state)
       {
          this(instance, methods);
          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
       {
          if (!methods.contains(method))
          {
             throw new SilentUnwindException();
          }

          if (state != null)
          {
             state.sync();
          }

          return method.invoke(instance, args);
       }
    }