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Date: 22 Apr 2001 07:36:57 -0000
Message-ID: <20010422073657.20444.qmail@apache.org>
From: donaldp@apache.org
To: jakarta-avalon-cvs@apache.org
Subject: cvs commit: jakarta-avalon/src/java/org/apache/excalibur/proxy
 ProxyClassLoader.java ProxyGenerator.java

donaldp     01/04/22 00:36:57

  Added:       src/java/org/apache/excalibur/proxy ProxyClassLoader.java
                        ProxyGenerator.java
  Log:
  Moved proxy code to excalibur
  
  Revision  Changes    Path
  1.1                  jakarta-avalon/src/java/org/apache/excalibur/proxy/ProxyClassLoader.java
  
  Index: ProxyClassLoader.java
  ===================================================================
  /*
   * Copyright (C) The Apache Software Foundation. All rights reserved.
   *
   * This software is published under the terms of the Apache Software License
   * version 1.1, a copy of which has been included with this distribution in
   * the LICENSE file.
   */
  package org.apache.excalibur.proxy;
  
  /**
   * Utility class to help load dynamically generated classes.
   *
   * @author <a href="mailto:donaldp@apache.org">Peter Donald</a>
   */
  public class ProxyClassLoader
      extends ClassLoader
  {
      public ProxyClassLoader( final ClassLoader parent )
      {
          super( parent );
      }
  
      public Class loadClass( final String name,
                              final boolean resolve,
                              final byte[] classData )
          throws ClassNotFoundException
      {
          final Class result =
              defineClass( name, classData, 0, classData.length );
  
          if( resolve )
          {
              resolveClass( result );
          }
  
          return result;
      }
  }
  
  
  
  
  1.1                  jakarta-avalon/src/java/org/apache/excalibur/proxy/ProxyGenerator.java
  
  Index: ProxyGenerator.java
  ===================================================================
  /**
   * Copyright (C) The Apache Software Foundation. All rights reserved.
   *
   * This software is published under the terms of the Apache Software License
   * version 1.1, a copy of which has been included with this distribution in
   * the LICENSE file.
   */
  package org.apache.excalibur.proxy;
  
  import gnu.bytecode.Access;
  import gnu.bytecode.ClassType;
  import gnu.bytecode.ClassTypeWriter;
  import gnu.bytecode.CodeAttr;
  import gnu.bytecode.Field;
  import gnu.bytecode.Scope;
  import gnu.bytecode.Type;
  import gnu.bytecode.Variable;
  import java.lang.reflect.Constructor;
  import java.lang.reflect.Method;
  import java.util.HashMap;
  import java.util.Iterator;
  import org.apache.log.LogKit;
  import org.apache.log.Logger;
  
  /**
   * A class to generate proxies for objects.
   *
   * @author <a href="mailto:donaldp@apache.org">Peter Donald</a>
   */
  public final class ProxyGenerator
  {
      protected final static boolean    DEBUG       = false;
      protected final static Logger     LOGGER      =
          ( DEBUG ) ? LogKit.getLoggerFor( "ProxyGenerator" ) : null;
  
      protected final static Object     MONITOR     = new Object();
      protected final static ClassType  BASE_CLASS  =
          (ClassType)Type.getType( "java.lang.Object" );
  
      protected static long             c_currentId;
  
      /**
       * Private constructor to block subclassing.
       *
       */
      private ProxyGenerator()
      {
      }
  
      /**
       * Way to generate unique id for each class.
       *
       * @return a unique id
       */
      protected static long getNextId()
      {
          synchronized( MONITOR )
          {
              return c_currentId++;
          }
      }
  
      /**
       * Generate a proxy for object with certain interfaces.
       *
       * @param object the object
       * @param interfaces[] the interfaces
       * @return the proxy object
       * @exception IllegalArgumentException if an error occurs
       */
      public static Object generateProxy( final Object object,
                                          final Class[] interfaces )
          throws IllegalArgumentException
      {
          if( DEBUG )
          {
              LOGGER.debug( "Generating proxy for " + object.getClass().getName() );
              LOGGER.debug( "Interfaces generating:" );
  
              for( int i = 0; i < interfaces.length; i++ )
              {
                  LOGGER.debug( interfaces[ i ].getName() );
              }
          }
  
          for( int i = 0; i < interfaces.length; i++ )
          {
              if( !interfaces[ i ].isInterface() )
              {
                  throw new IllegalArgumentException( "Class " + interfaces[ i ].getName() +
                                                      " is not an interface" );
              }
              else if( !interfaces[ i ].isInstance( object ) )
              {
                  throw new IllegalArgumentException( "Object does not implement interface " +
                                                      interfaces[ i ].getName() );
              }
          }
  
          final HashMap methodSet = determineMethods( interfaces );
  
          final String classname = "org.apache.avalon.tmp.Proxy" + getNextId();
  
          if( DEBUG ) { LOGGER.debug( "Generating proxy named " + classname ); }
  
          final ClassType proxy = createProxyType( classname );
  
          //generate all interface declarations
          generateInterfaces( proxy, interfaces );
  
          final ClassType target =
              (ClassType)Type.make( object.getClass() );
  
          target.doFixups();
  
          //generate variables/constructor
          generateBase( proxy, target );
  
          //generate methods
          final Iterator methods = methodSet.values().iterator();
          while( methods.hasNext() )
          {
              generateMethod( proxy, target, (Method)methods.next() );
          }
  
          if( DEBUG )
          {
              //help while debugging
              //ClassTypeWriter.print( target, System.out, 0 );
              //try { proxy.writeToFile( "/tmp/" + classname.replace('.','/') + ".class" ); }
              //catch( final Throwable throwable ) { throwable.printStackTrace(); }
          }
  
          proxy.doFixups();
  
          Class proxyClass = null;
          try
          {
              final byte[] classData = proxy.writeToArray();
  
              //extremely inneficient - must fix in future
              final ProxyClassLoader classLoader =
                  new ProxyClassLoader( object.getClass().getClassLoader() );
  
              proxyClass = classLoader.loadClass( classname, true, classData );
              final Constructor ctor =
                  proxyClass.getConstructor( new Class[] { object.getClass() } );
              return ctor.newInstance( new Object[] { object } );
          }
          catch( final Throwable throwable ) { throwable.printStackTrace(); }
  
          return null;
      }
  
      /**
       * Create Proxy class.
       *
       * @param classname name of class
       * @return the proxy class
       */
      protected static ClassType createProxyType( final String classname )
      {
          final ClassType proxy = new ClassType( classname );
          proxy.setModifiers( Access.PUBLIC | /*ACC_SUPER*/ 0x0020 | Access.FINAL );
          proxy.setSuper( BASE_CLASS );
  
          return proxy;
      }
  
      /**
       * generate the list of Interfaces class implements.
       *
       * @param proxy the proxy class
       * @param interfaces[] the interfaces to add
       */
      protected static void generateInterfaces( final ClassType proxy,
                                                final Class[] interfaces )
      {
          final ClassType[] interfaceTypes = new ClassType[ interfaces.length ];
  
          for( int i = 0; i < interfaceTypes.length; i++ )
          {
              interfaceTypes[ i ] = (ClassType)Type.getType( interfaces[ i ].getName() );
          }
  
          proxy.setInterfaces( interfaceTypes );
      }
  
      /**
       * Generate code for wrapper method.
       *
       * @param proxy the class to add to
       * @param target the class wrapping
       * @param method the method to wrap
       */
      protected static void generateMethod( final ClassType proxy,
                                            final ClassType target,
                                            final Method method )
      {
          final Class[] parameters = method.getParameterTypes();
          final Type[] parameterTypes = new Type[ parameters.length ];
  
          for( int i = 0; i < parameterTypes.length; i++ )
          {
              parameterTypes[ i ] = Type.getType( parameters[ i ].getName() );
          }
  
          final Type returnType =
              Type.getType( method.getReturnType().getName() );
  
          final gnu.bytecode.Method newMethod =
              proxy.addMethod( method.getName(),
                               Access.PUBLIC,
                               parameterTypes,
                               returnType );
  
          newMethod.init_param_slots();
          newMethod.pushScope();
          final CodeAttr code = newMethod.getCode();
  
          //put m_core on stack;
          final Field field = proxy.getField( "m_core" );
  
          code.emitPushThis();
          code.emitGetField( field );
  
          for( int i = 0; i < parameterTypes.length; i++ )
          {
              code.emitLoad( code.getArg( 1 + i ) );
          }
  
          //call target method
          final gnu.bytecode.Method targetMethod =
              target.getMethod( method.getName(), parameterTypes );
          code.emitInvokeVirtual( targetMethod );
  
          //return
          code.emitReturn();
          newMethod.popScope();
      }
  
      /**
       * Generate constructor code and field data.
       *
       * @param proxy the representation of class so far
       * @param target the type that is wrapped
       */
      protected static void generateBase( final ClassType proxy,
                                          final Type target )
      {
          final Field field = proxy.addField( "m_core", target );
          field.flags |= Access.PRIVATE;
  
          final gnu.bytecode.Method constructor =
              proxy.addMethod( "<init>",
                               Access.PUBLIC,
                               new Type[] { target },
                               Type.void_type );
  
          final gnu.bytecode.Method superConstructor
              = proxy.getSuperclass().addMethod( "<init>",
                                                 Access.PUBLIC,
                                                 null,
                                                 Type.void_type );
  
          constructor.init_param_slots();
          constructor.pushScope();
          final CodeAttr code = constructor.getCode();
  
          //super();
          code.emitPushThis();
          code.emitInvokeSpecial( superConstructor );
  
          //m_core = param1;
          code.emitPushThis();
          code.emitLoad( code.getArg( 1 ) );
          code.emitPutField( field );
  
          //return
          code.emitReturn();
  
          constructor.popScope();
      }
  
      /**
       * Determine the methods that must be implemented to
       * implement interface, eliminating duplicates.
       *
       * @param interfaces[] the interfaces to extract methods from
       * @return methods
       */
      protected static HashMap determineMethods( final Class[] interfaces )
      {
          final HashMap methodSet = new HashMap();
          final StringBuffer sb = new StringBuffer();
  
          for( int i = 0; i < interfaces.length; i++ )
          {
              if( DEBUG )
              {
                  LOGGER.debug( "Scanning interface " + interfaces[ i ].getName() +
                                " for methods" );
              }
  
              final Method[] methods = interfaces[ i ].getMethods();
  
              //for each method generate a pseudo signature
              //Add the method to methodSet under that signature.
              //This is to ensure that only one version of a method is
              //entered into set even if multiple interfaces declare it
  
              for( int j = 0; j < methods.length; j++ )
              {
                  sb.append( methods[ j ].getName() );
                  sb.append( '(' );
  
                  final Class[] parameters = methods[ j ].getParameterTypes();
  
                  for( int k = 0; k < parameters.length; k++ )
                  {
                      sb.append( parameters[ k ].getName() );
                      sb.append( ' ' );
                  }
  
                  sb.append( ";)" );
  
                  if( DEBUG )
                  {
                      LOGGER.debug( "Found method with pseudo-signature " + sb );
                  }
  
                  methodSet.put( sb.toString(), methods[ j ] );
                  sb.setLength( 0 );
              }
          }
  
          return methodSet;
      }
  }
  
  
  

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