Hibernate example source code file (JavassistLazyInitializer.java)

This example Hibernate source code file (JavassistLazyInitializer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Hibernate tags/keywords

class, class, compositetype, finalize_filter, hibernateexception, hibernateproxy, io, javassistlazyinitializer, javassistlazyinitializer, method, method, object, object, proxyfactory, reflection, throwable

The Hibernate JavassistLazyInitializer.java source code

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2010, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.proxy.pojo.javassist;

import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import javassist.util.proxy.MethodFilter;
import javassist.util.proxy.MethodHandler;
import javassist.util.proxy.ProxyFactory;
import javassist.util.proxy.ProxyObject;
import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SessionImplementor;
import org.hibernate.internal.CoreMessageLogger;
import org.hibernate.internal.util.ReflectHelper;
import org.hibernate.proxy.HibernateProxy;
import org.hibernate.proxy.pojo.BasicLazyInitializer;
import org.hibernate.type.CompositeType;
import org.jboss.logging.Logger;

/**
 * A Javassist-based lazy initializer proxy.
 *
 * @author Muga Nishizawa
 */
public class JavassistLazyInitializer extends BasicLazyInitializer implements MethodHandler {

    private static final CoreMessageLogger LOG = Logger.getMessageLogger(CoreMessageLogger.class,
                                                                       JavassistLazyInitializer.class.getName());

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

	private Class[] interfaces;
	private boolean constructed = false;

	private JavassistLazyInitializer(
			final String entityName,
	        final Class persistentClass,
	        final Class[] interfaces,
	        final Serializable id,
	        final Method getIdentifierMethod,
	        final Method setIdentifierMethod,
	        final CompositeType componentIdType,
	        final SessionImplementor session) {
		super( entityName, persistentClass, id, getIdentifierMethod, setIdentifierMethod, componentIdType, session );
		this.interfaces = interfaces;
	}

	public static HibernateProxy getProxy(
			final String entityName,
	        final Class persistentClass,
	        final Class[] interfaces,
	        final Method getIdentifierMethod,
	        final Method setIdentifierMethod,
	        CompositeType componentIdType,
	        final Serializable id,
	        final SessionImplementor session) throws HibernateException {
		// note: interface is assumed to already contain HibernateProxy.class
		try {
			final JavassistLazyInitializer instance = new JavassistLazyInitializer(
					entityName,
			        persistentClass,
			        interfaces,
			        id,
			        getIdentifierMethod,
			        setIdentifierMethod,
			        componentIdType,
			        session
			);
			ProxyFactory factory = new ProxyFactory();
			factory.setSuperclass( interfaces.length == 1 ? persistentClass : null );
			factory.setInterfaces( interfaces );
			factory.setFilter( FINALIZE_FILTER );
			Class cl = factory.createClass();
			final HibernateProxy proxy = ( HibernateProxy ) cl.newInstance();
			( ( ProxyObject ) proxy ).setHandler( instance );
			instance.constructed = true;
			return proxy;
		}
		catch ( Throwable t ) {
            LOG.error(LOG.javassistEnhancementFailed(entityName), t);
            throw new HibernateException(LOG.javassistEnhancementFailed(entityName), t);
		}
	}

	public static HibernateProxy getProxy(
			final Class factory,
	        final String entityName,
	        final Class persistentClass,
	        final Class[] interfaces,
	        final Method getIdentifierMethod,
	        final Method setIdentifierMethod,
	        final CompositeType componentIdType,
	        final Serializable id,
	        final SessionImplementor session) throws HibernateException {

		final JavassistLazyInitializer instance = new JavassistLazyInitializer(
				entityName,
		        persistentClass,
		        interfaces, id,
		        getIdentifierMethod,
		        setIdentifierMethod,
		        componentIdType,
		        session
		);

		final HibernateProxy proxy;
		try {
			proxy = ( HibernateProxy ) factory.newInstance();
		}
		catch ( Exception e ) {
			throw new HibernateException(
					"Javassist Enhancement failed: "
					+ persistentClass.getName(), e
			);
		}
		( ( ProxyObject ) proxy ).setHandler( instance );
		instance.constructed = true;
		return proxy;
	}

	public static Class getProxyFactory(
			Class persistentClass,
	        Class[] interfaces) throws HibernateException {
		// note: interfaces is assumed to already contain HibernateProxy.class

		try {
			ProxyFactory factory = new ProxyFactory();
			factory.setSuperclass( interfaces.length == 1 ? persistentClass : null );
			factory.setInterfaces( interfaces );
			factory.setFilter( FINALIZE_FILTER );
			return factory.createClass();
		}
		catch ( Throwable t ) {
            LOG.error(LOG.javassistEnhancementFailed(persistentClass.getName()), t);
            throw new HibernateException(LOG.javassistEnhancementFailed(persistentClass.getName()), t);
		}
	}

	public Object invoke(
			final Object proxy,
			final Method thisMethod,
			final Method proceed,
			final Object[] args) throws Throwable {
		if ( this.constructed ) {
			Object result;
			try {
				result = this.invoke( thisMethod, args, proxy );
			}
			catch ( Throwable t ) {
				throw new Exception( t.getCause() );
			}
			if ( result == INVOKE_IMPLEMENTATION ) {
				Object target = getImplementation();
				final Object returnValue;
				try {
					if ( ReflectHelper.isPublic( persistentClass, thisMethod ) ) {
						if ( !thisMethod.getDeclaringClass().isInstance( target ) ) {
							throw new ClassCastException( target.getClass().getName() );
						}
						returnValue = thisMethod.invoke( target, args );
					}
					else {
						if ( !thisMethod.isAccessible() ) {
							thisMethod.setAccessible( true );
						}
						returnValue = thisMethod.invoke( target, args );
					}
					return returnValue == target ? proxy : returnValue;
				}
				catch ( InvocationTargetException ite ) {
					throw ite.getTargetException();
				}
			}
			else {
				return result;
			}
		}
		else {
			// while constructor is running
			if ( thisMethod.getName().equals( "getHibernateLazyInitializer" ) ) {
				return this;
			}
			else {
				return proceed.invoke( proxy, args );
			}
		}
	}

	@Override
    protected Object serializableProxy() {
		return new SerializableProxy(
				getEntityName(),
		        persistentClass,
		        interfaces,
		        getIdentifier(),
		        ( isReadOnlySettingAvailable() ? Boolean.valueOf( isReadOnly() ) : isReadOnlyBeforeAttachedToSession() ),
		        getIdentifierMethod,
		        setIdentifierMethod,
		        componentIdType
		);
	}
}