/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.proxy.factory.javassist;
import javassist.CannotCompileException;
import javassist.CtClass;
import javassist.CtConstructor;
import javassist.CtMethod;
import org.apache.commons.proxy.Invocation;
import org.apache.commons.proxy.ProxyUtils;
import java.lang.ref.WeakReference;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import java.util.WeakHashMap;
/**
* A <a href="http://www.jboss.org/products/javassist">Javassist</a>-based {@link Invocation} implementation. This
* class actually serves as the superclass for all <a href="http://www.jboss.org/products/javassist">Javassist</a>-based
* method invocations. Subclasses are dynamically created to deal with specific interface methods (they're hard-wired).
*
* @author James Carman
* @since 1.0
*/
public abstract class JavassistInvocation implements Invocation
{
//----------------------------------------------------------------------------------------------------------------------
// Fields
//----------------------------------------------------------------------------------------------------------------------
private static WeakHashMap loaderToClassCache = new WeakHashMap();
protected final Method method;
protected final Object target;
protected final Object[] arguments;
//----------------------------------------------------------------------------------------------------------------------
// Static Methods
//----------------------------------------------------------------------------------------------------------------------
private static String createCastExpression( Class type, String objectToCast )
{
if( !type.isPrimitive() )
{
return "( " + ProxyUtils.getJavaClassName( type ) + " )" + objectToCast;
}
else
{
return "( ( " + ProxyUtils.getWrapperClass( type ).getName() + " )" + objectToCast + " )." +
type.getName() + "Value()";
}
}
private static Class createInvocationClass( ClassLoader classLoader, Method interfaceMethod )
throws CannotCompileException
{
Class invocationClass;
final CtClass ctClass = JavassistUtils.createClass(
getSimpleName( interfaceMethod.getDeclaringClass() ) + "_" + interfaceMethod.getName() +
"_invocation",
JavassistInvocation.class );
final CtConstructor constructor = new CtConstructor(
JavassistUtils.resolve( new Class[]{ Method.class, Object.class, Object[].class } ),
ctClass );
constructor.setBody( "{\n\tsuper($$);\n}" );
ctClass.addConstructor( constructor );
final CtMethod proceedMethod = new CtMethod( JavassistUtils.resolve( Object.class ), "proceed",
JavassistUtils.resolve( new Class[0] ), ctClass );
final Class[] argumentTypes = interfaceMethod.getParameterTypes();
final StringBuffer proceedBody = new StringBuffer( "{\n" );
if( !Void.TYPE.equals( interfaceMethod.getReturnType() ) )
{
proceedBody.append( "\treturn " );
if( interfaceMethod.getReturnType().isPrimitive() )
{
proceedBody.append( "new " );
proceedBody.append( ProxyUtils.getWrapperClass( interfaceMethod.getReturnType() ).getName() );
proceedBody.append( "( " );
}
}
else
{
proceedBody.append( "\t" );
}
proceedBody.append( "( (" );
proceedBody.append( ProxyUtils.getJavaClassName( interfaceMethod.getDeclaringClass() ) );
proceedBody.append( " )target )." );
proceedBody.append( interfaceMethod.getName() );
proceedBody.append( "(" );
for( int i = 0; i < argumentTypes.length; ++i )
{
final Class argumentType = argumentTypes[i];
proceedBody.append( createCastExpression( argumentType, "arguments[" + i + "]" ) );
if( i != argumentTypes.length - 1 )
{
proceedBody.append( ", " );
}
}
if( !Void.TYPE.equals( interfaceMethod.getReturnType() ) && interfaceMethod.getReturnType().isPrimitive() )
{
proceedBody.append( ") );\n" );
}
else
{
proceedBody.append( ");\n" );
}
if( Void.TYPE.equals( interfaceMethod.getReturnType() ) )
{
proceedBody.append( "\treturn null;\n" );
}
proceedBody.append( "}" );
final String body = proceedBody.toString();
proceedMethod.setBody( body );
ctClass.addMethod( proceedMethod );
invocationClass = ctClass.toClass( classLoader );
return invocationClass;
}
private static Map getClassCache( ClassLoader classLoader )
{
Map cache = ( Map ) loaderToClassCache.get( classLoader );
if( cache == null )
{
cache = new HashMap();
loaderToClassCache.put( classLoader, cache );
}
return cache;
}
/**
* Returns a method invocation class specifically coded to invoke the supplied interface method.
*
* @param classLoader the classloader to use
* @param interfaceMethod the interface method
* @return a method invocation class specifically coded to invoke the supplied interface method
* @throws CannotCompileException if a compilation error occurs
*/
synchronized static Class getMethodInvocationClass( ClassLoader classLoader,
Method interfaceMethod )
throws CannotCompileException
{
final Map classCache = getClassCache( classLoader );
final String key = toClassCacheKey( interfaceMethod );
final WeakReference invocationClassRef = ( WeakReference ) classCache.get( key );
Class invocationClass;
if( invocationClassRef == null )
{
invocationClass = createInvocationClass( classLoader, interfaceMethod );
classCache.put( key, new WeakReference( invocationClass ) );
}
else
{
synchronized( invocationClassRef )
{
invocationClass = ( Class ) invocationClassRef.get();
if( invocationClass == null )
{
invocationClass = createInvocationClass( classLoader, interfaceMethod );
classCache.put( key, new WeakReference( invocationClass ) );
}
}
}
return invocationClass;
}
private static String getSimpleName( Class c )
{
final String name = c.getName();
final int ndx = name.lastIndexOf( '.' );
return ndx == -1 ? name : name.substring( ndx + 1 );
}
private static String toClassCacheKey( Method method )
{
return String.valueOf( method );
}
//----------------------------------------------------------------------------------------------------------------------
// Constructors
//----------------------------------------------------------------------------------------------------------------------
public JavassistInvocation( Method method, Object target, Object[] arguments )
{
this.method = method;
this.target = target;
this.arguments = arguments;
}
//----------------------------------------------------------------------------------------------------------------------
// Invocation Implementation
//----------------------------------------------------------------------------------------------------------------------
public Object[] getArguments()
{
return arguments;
}
public Method getMethod()
{
return method;
}
public Object getProxy()
{
return target;
}
}