cgliblazyinitializer.java

hibernate-3.1.3-all-src.zip 面向对象的访问数据库工具

// $Id: CGLIBLazyInitializer.java 8476 2005-10-27 12:00:59Z oneovthafew $
package org.hibernate.proxy;

import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.CallbackFilter;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.Factory;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.proxy.NoOp;

import org.hibernate.HibernateException;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.type.AbstractComponentType;
import org.hibernate.util.ReflectHelper;

import org.apache.commons.logging.LogFactory;

/**
 * A <tt>LazyInitializer</tt> implemented using the CGLIB bytecode generation library
 */
public final class CGLIBLazyInitializer extends BasicLazyInitializer implements MethodInterceptor {

	
	private static final Class[] CALLBACK_TYPES = new Class[]{ MethodInterceptor.class,NoOp.class };
	
	private static final CallbackFilter FINALIZE_FILTER = new CallbackFilter() {
		public int accept(Method method) {
			if ( method.getParameterTypes().length == 0 && method.getName().equals("finalize") ){
				return 1;
			}
			else {
				return 0;
			}
		}
	};

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

	static HibernateProxy getProxy(final String entityName, final Class persistentClass,
			final Class[] interfaces, final Method getIdentifierMethod,
			final Method setIdentifierMethod, AbstractComponentType componentIdType,
			final Serializable id, final SessionImplementor session) throws HibernateException {
		// note: interfaces is assumed to already contain HibernateProxy.class
		
		try {
			final CGLIBLazyInitializer instance = new CGLIBLazyInitializer(
					entityName,
					persistentClass,
					interfaces,
					id,
					getIdentifierMethod,
					setIdentifierMethod,
					componentIdType,
					session 
				);
			
			final HibernateProxy proxy = (HibernateProxy) Enhancer.create(
						interfaces.length == 1 ? persistentClass : null, 
						interfaces,
						FINALIZE_FILTER, 
						new Callback[]{ instance, NoOp.INSTANCE }
					);
			
			instance.constructed = true;
			return proxy;
		}
		catch (Throwable t) {
			LogFactory.getLog( BasicLazyInitializer.class )
				.error( "CGLIB Enhancement failed: " + entityName, t );
			throw new HibernateException( "CGLIB Enhancement failed: " + 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 AbstractComponentType componentIdType, final Serializable id,
			final SessionImplementor session) throws HibernateException {
		
		final CGLIBLazyInitializer instance = new CGLIBLazyInitializer(
				entityName,
				persistentClass,
				interfaces,
				id,
				getIdentifierMethod,
				setIdentifierMethod,
				componentIdType,
				session 
			);
		
		final HibernateProxy proxy;
		try {
			proxy = (HibernateProxy) factory.newInstance();
		}
		catch (Exception e) {
			throw new HibernateException( "CGLIB Enhancement failed: " + persistentClass.getName(), e );
		}
		( (Factory) proxy ).setCallback( 0, 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 {

			Enhancer en = new Enhancer();
			en.setUseCache( false );
			en.setInterceptDuringConstruction( false );
			
			en.setCallbackTypes( CALLBACK_TYPES );
			en.setCallbackFilter( FINALIZE_FILTER );
			
			en.setSuperclass( interfaces.length == 1 ? persistentClass : null );
			en.setInterfaces( interfaces );

			return en.createClass();

		}
		catch (Throwable t) {
			LogFactory.getLog( BasicLazyInitializer.class )
				.error( "CGLIB Enhancement failed: " + persistentClass.getName(), t );
			throw new HibernateException( "CGLIB Enhancement failed: " + persistentClass.getName(), t );
		}
	}

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

	public Object intercept(final Object proxy, final Method method, final Object[] args,
			final MethodProxy methodProxy) throws Throwable {
		if ( constructed ) {
			
			Object result = invoke( method, args, proxy );
			if ( result == INVOKE_IMPLEMENTATION ) {
				Object target = getImplementation();
				final Object returnValue;
				if ( ReflectHelper.isPublic( persistentClass, method ) ) {
					returnValue = methodProxy.invoke( target, args );
				}
				else {
					if ( !method.isAccessible() ) method.setAccessible( true );
					try {
						returnValue = method.invoke( target, args );
					}
					catch (InvocationTargetException ite) {
						throw ite.getTargetException();
					}
				}
				return returnValue == target ? proxy : returnValue;
			}
			else {
				return result;
			}
			
		}
		else {
			
			// while constructor is running
			if ( method.getName().equals( "getHibernateLazyInitializer" ) ) {
				return this;
			}
			else {
				return methodProxy.invokeSuper( proxy, args );
			}
			
		}
	}

	protected Object serializableProxy() {
		return new SerializableProxy(
				getEntityName(),
				persistentClass,
				interfaces,
				getIdentifier(),
				getIdentifierMethod,
				setIdentifierMethod,
				componentIdType 
			);
	}

}