cgliblazyinitializer.java

用Java实现的23个常用设计模式源代码

//$Id: CGLIBLazyInitializer.java,v 1.9.2.7 2003/11/19 15:45:37 oneovthafew Exp $
package net.sf.hibernate.proxy;

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

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.hibernate.HibernateException;
import net.sf.hibernate.engine.SessionImplementor;

import org.apache.commons.logging.LogFactory;


/**
 * A <tt>LazyInitializer</tt> implemented using the CGLIB bytecode generation library
 */
public final class CGLIBLazyInitializer extends LazyInitializer implements MethodInterceptor {
	
	private Class[] interfaces;
	
	public static HibernateProxy getProxy(Class persistentClass, Class[] interfaces, Method getIdentifierMethod, Method setIdentifierMethod, Serializable id, SessionImplementor session) throws HibernateException {
		//note: interfaces is assumed to already contain HibernateProxy.class
		try {
			return (HibernateProxy) Enhancer.create(
				(interfaces.length==1) ?
					persistentClass :
					null,
				interfaces,
				new CGLIBLazyInitializer(persistentClass, interfaces, id, getIdentifierMethod, setIdentifierMethod, session)
			);
		}
		catch (Throwable t) {
			LogFactory.getLog(LazyInitializer.class).error("CGLIB Enhancement failed", t);
			throw new HibernateException( "CGLIB Enhancement failed", t );
		}
	}
	
	public static HibernateProxy getProxy(Factory factory, Class persistentClass, Class[] interfaces, Method getIdentifierMethod, Method setIdentifierMethod, Serializable id, SessionImplementor session) throws HibernateException {
		return (HibernateProxy) factory.newInstance( 
			new CGLIBLazyInitializer(persistentClass, interfaces, id, getIdentifierMethod, setIdentifierMethod, session) 
		);
	}
	
	public static Factory getProxyFactory(Class persistentClass, Class[] interfaces) throws HibernateException {
		//note: interfaces is assumed to already contain HibernateProxy.class
		try {
			return (Factory) Enhancer.create(
				(interfaces.length==1) ?
					persistentClass :
					null,
				interfaces,
				NULL_METHOD_INTERCEPTOR
			);
		}
		catch (Throwable t) {
			LogFactory.getLog(LazyInitializer.class).error("CGLIB Enhancement failed", t);
			throw new HibernateException( "CGLIB Enhancement failed", t );
		}
	}
	
	private CGLIBLazyInitializer(Class persistentClass, Class[] interfaces, Serializable id, Method getIdentifierMethod, Method setIdentifierMethod, SessionImplementor session) {
		super(persistentClass, id, getIdentifierMethod, setIdentifierMethod, session);
		this.interfaces = interfaces;
	}
	
	public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
		Object result = invoke(method, args, obj);
		if (result==INVOKE_IMPLEMENTATION) {
			return proxy.invoke( getImplementation(), args );
		}
		else {
			return result;
		}
	}
	
	protected Object serializableProxy() {
		return new SerializableProxy(persistentClass, interfaces, id, getIdentifierMethod, setIdentifierMethod);
	}
	
	private static final MethodInterceptor NULL_METHOD_INTERCEPTOR = new MethodInterceptor() {
		public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable { return null; }
	};
}