/*
* Copyright 2009 Niclas Hedhman.
*
* Licensed 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.qi4j.api.composite;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import org.qi4j.api.injection.scope.Uses;
/**
* Generic decorator mixin that allows a Composite to wrap
* any other Composite as long as they share an interface.
* <p>
* Can be used to effectively implement
* singleton mixins, since the decorated object can be shared between
* many instances.
* </p>
*/
public class DecoratorMixin
implements InvocationHandler
{
private Object delegate;
public DecoratorMixin( @Uses Object delegate )
{
if( delegate instanceof Class )
{
Thread.dumpStack();
}
this.delegate = delegate;
}
@Override
public Object invoke( Object object, Method method, Object[] args )
throws Throwable
{
if( delegate instanceof InvocationHandler )
{
InvocationHandler handler = (InvocationHandler) delegate;
return handler.invoke( object, method, args );
}
else
{
try
{
return method.invoke( delegate, args );
}
catch( InvocationTargetException e )
{
throw e.getCause();
}
catch( IllegalArgumentException e )
{
String message = constructMessage( method, args );
throw new IllegalArgumentException( message, e );
}
}
}
private String constructMessage( Method method, Object[] args )
{
StringBuilder builder = new StringBuilder();
builder.append( "\nmethod: " );
builder.append( method.getDeclaringClass().getName() );
builder.append( "." );
builder.append( method.getName() );
builder.append( "\ndelegate: " );
builder.append( delegate );
builder.append( "\ndelegateType: " );
builder.append( delegate == null ? "n/a" : delegate.getClass().getName() );
builder.append( "\narguments: \n" );
for( Object arg : args )
{
builder.append( " " );
Class argClass = arg.getClass();
if( Proxy.isProxyClass( argClass ) )
{
builder.append( Proxy.getInvocationHandler( arg ).getClass().getName() );
}
else
{
builder.append( argClass.getName() );
}
builder.append( '\n' );
}
return builder.toString();
}
}