ProxyFactoryFactoryImpl.java

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.bytecode.internal.javassist;

import java.lang.reflect.Method;
import java.util.HashMap;

import javassist.util.proxy.MethodFilter;
import javassist.util.proxy.MethodHandler;
import javassist.util.proxy.Proxy;

import org.hibernate.AssertionFailure;
import org.hibernate.HibernateException;
import org.hibernate.bytecode.spi.BasicProxyFactory;
import org.hibernate.bytecode.spi.ProxyFactoryFactory;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.proxy.ProxyFactory;
import org.hibernate.proxy.pojo.javassist.JavassistProxyFactory;

/**
 * A factory for Javassist-based {@link ProxyFactory} instances.
 *
 * @author Steve Ebersole
 */
public class ProxyFactoryFactoryImpl implements ProxyFactoryFactory {

	/**
	 * Builds a Javassist-based proxy factory.
	 *
	 * @return a new Javassist-based proxy factory.
	 */
	@Override
	public ProxyFactory buildProxyFactory(SessionFactoryImplementor sessionFactory) {
		return new JavassistProxyFactory();
	}

	/**
	 * Constructs a BasicProxyFactoryImpl
	 *
	 * @param superClass The abstract super class (or null if none).
	 * @param interfaces Interfaces to be proxied (or null if none).
	 *
	 * @return The constructed BasicProxyFactoryImpl
	 */
	@Override
	public BasicProxyFactory buildBasicProxyFactory(Class superClass, Class[] interfaces) {
		return new BasicProxyFactoryImpl( superClass, interfaces );
	}

	private static class BasicProxyFactoryImpl implements BasicProxyFactory {
		private final Class proxyClass;

		public BasicProxyFactoryImpl(Class superClass, Class[] interfaces) {
			if ( superClass == null && ( interfaces == null || interfaces.length < 1 ) ) {
				throw new AssertionFailure( "attempting to build proxy without any superclass or interfaces" );
			}

			final javassist.util.proxy.ProxyFactory factory = new javassist.util.proxy.ProxyFactory();
			factory.setFilter( FINALIZE_FILTER );
			if ( superClass != null ) {
				factory.setSuperclass( superClass );
			}
			if ( interfaces != null && interfaces.length > 0 ) {
				factory.setInterfaces( interfaces );
			}
			proxyClass = factory.createClass();
		}

		public Object getProxy() {
			try {
				final Proxy proxy = (Proxy) proxyClass.newInstance();
				proxy.setHandler( new PassThroughHandler( proxy, proxyClass.getName() ) );
				return proxy;
			}
			catch ( Throwable t ) {
				throw new HibernateException( "Unable to instantiated proxy instance" );
			}
		}

		public boolean isInstance(Object object) {
			return proxyClass.isInstance( object );
		}
	}

	private static final MethodFilter FINALIZE_FILTER = new MethodFilter() {
		public boolean isHandled(Method m) {
			// skip finalize methods
			return !( m.getParameterCount() == 0 && m.getName().equals( "finalize" ) );
		}
	};

	private static class PassThroughHandler implements MethodHandler {
		private HashMap data = new HashMap();
		private final Object proxiedObject;
		private final String proxiedClassName;

		public PassThroughHandler(Object proxiedObject, String proxiedClassName) {
			this.proxiedObject = proxiedObject;
			this.proxiedClassName = proxiedClassName;
		}

		@SuppressWarnings("unchecked")
		public Object invoke(
				Object object,
				Method method,
				Method method1,
				Object[] args) throws Exception {
			final String name = method.getName();
			if ( "toString".equals( name ) ) {
				return proxiedClassName + "@" + System.identityHashCode( object );
			}
			else if ( "equals".equals( name ) ) {
				return proxiedObject == object;
			}
			else if ( "hashCode".equals( name ) ) {
				return System.identityHashCode( object );
			}

			final boolean hasGetterSignature = method.getParameterCount() == 0
					&& method.getReturnType() != null;
			final boolean hasSetterSignature = method.getParameterCount() == 1
					&& ( method.getReturnType() == null || method.getReturnType() == void.class );

			if ( name.startsWith( "get" ) && hasGetterSignature ) {
				final String propName = name.substring( 3 );
				return data.get( propName );
			}
			else if ( name.startsWith( "is" ) && hasGetterSignature ) {
				final String propName = name.substring( 2 );
				return data.get( propName );
			}
			else if ( name.startsWith( "set" ) && hasSetterSignature) {
				final String propName = name.substring( 3 );
				data.put( propName, args[0] );
				return null;
			}
			else {
				// todo : what else to do here?
				return null;
			}
		}
	}
}