Java动态代理与CGLib

Java动态代理机制是一种强大的编译时生成代码的机制。
比如以下例子，其实就是在编译后生成一个HelloImpl的代理类。它要求被代理的方法必须来自于一个借口，如例子中的Hello

package org.mark.proxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class TestDynamicProxy {
	public static interface Hello {
		public void sayHello();
	}
	
	public static class HelloImpl implements Hello	{

		@Override
		public void sayHello() {
			// TODO Auto-generated method stub
			System.out.println("say hello");
		}
		
	}
	
	public static class ProxyTest implements InvocationHandler {
		Object originalObj;
		
		Object bind(Object originalObj) {
			this.originalObj = originalObj;
			
			return Proxy.newProxyInstance(originalObj.getClass().getClassLoader(), originalObj.getClass().getInterfaces(), this);
		}
		
		@Override
		public Object invoke(Object proxy, Method method, Object[] args)
				throws Throwable {
			System.out.println("DynamicProxy invocated!");
			return method.invoke(originalObj, args);
		}
		
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Hello hello = (Hello) new ProxyTest().bind(new HelloImpl());
		hello.sayHello();
	}

}

那么问题来了，挖掘机技术哪家强？

如果说一个普通的类，有一个方法，该方法并非实现接口所得，那么它的动态代理应该怎么做呢？首先Java的JDK内置动态代理无法做到，因为它要求代理的方法必须来自于借口，所以可以用CGLib来做此类的代理行为。CGLIB具有简单易用，它的运行速度要远远快于JDK的Proxy动态代理。

如下例子程序

package org.mark.proxy;

import java.lang.reflect.Method;

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

public class TestCGLib {
	public static class InfoManager {
		public void create() {
			System.out.println("Create a record");
		}
	}
	
	public static class InfoManagerFactory {
		public static InfoManager getInstance(CGLibProxy proxy) {
			Enhancer enhancer = new Enhancer();
			enhancer.setSuperclass(InfoManager.class);
			enhancer.setCallback(proxy);
			return (InfoManager)enhancer.create();
		}
	}
	
	public static class CGLibProxy implements MethodInterceptor {
		private String name;
		
		public CGLibProxy(String name) {
			this.name = name;
		}
		
		@Override
		public Object intercept(Object arg0, Method arg1, Object[] arg2,
				MethodProxy arg3) throws Throwable {
			if(!name.equals("Test")) {
				System.out.println("Name is not Test, cglib ignored");
				return null;
			}
			System.out.println("cglib proxy called");
			return arg3.invokeSuper(arg0, arg2);
		}
		
	}
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		InfoManager manager = InfoManagerFactory.getInstance(new CGLibProxy("Test"));
		manager.create();
		
		InfoManager manager2 = InfoManagerFactory.getInstance(new CGLibProxy("Test2"));
		manager2.create();
	}

}