Cglib简单学习（2）

文章转自

http://www.cnblogs.com/icejoywoo/archive/2011/06/05/2072970.html

cglib 是一个强大的, 高效高质的代码生成库.

简单的使用方法

Enhancer中有几个常用的方法, setSuperClass和setCallback, 设置好了SuperClass后, 可以使用create制作代理对象了

Enhancer enhancer = new Enhancer();enhancer.setSuperclass(EnhancerDemo.class);enhancer.setCallback(new MethodInterceptorImpl());EnhancerDemo demo = (EnhancerDemo) enhancer.create();

实现MethodInterceptor接口

private static class MethodInterceptorImpl implements MethodInterceptor {         @Override        public Object intercept(Object obj, Method method, Object[] args,                MethodProxy proxy) throws Throwable {            System.out.println("Before invoke " + method);            Object result = proxy.invokeSuper(obj, args);            System.out.println("After invoke" + method);            return result;        }             }

intercept方法, Object result = proxy.invokeSuper(obj, args)调用了原来的方法, 在这个调用前后可以添加其他的逻辑, 相当于AspectJ的around

完整代码如下:

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 EnhancerDemo {    public static void main(String[] args) {        Enhancer enhancer = new Enhancer();        enhancer.setSuperclass(EnhancerDemo.class);        enhancer.setCallback(new MethodInterceptorImpl());                 EnhancerDemo demo = (EnhancerDemo) enhancer.create();                 demo.test();                 System.out.println(demo);    }         public void test() {        System.out.println("EnhancerDemo test()");    }         private static class MethodInterceptorImpl implements MethodInterceptor {         @Override        public Object intercept(Object obj, Method method, Object[] args,                MethodProxy proxy) throws Throwable {            System.err.println("Before invoke " + method);            Object result = proxy.invokeSuper(obj, args);            System.err.println("After invoke" + method);            return result;        }             }}

运行结果如下:

?

Before invoke publicvoidEnhancerDemo.test()

EnhancerDemo test()

After invokepublic voidEnhancerDemo.test()

Before invoke publicjava.lang.String java.lang.Object.toString()

Before invoke publicnativeint java.lang.Object.hashCode()

After invokepublic nativeintjava.lang.Object.hashCode()

After invokepublic java.lang.String java.lang.Object.toString()

EnhancerDemo$$EnhancerByCGLIB$$bc9b2066@1621e42

我们可以看到System.out.println(demo), demo首先调用了toString()方法, 然后又调用了hashCod, 我们可以查看toString的源代码

public String toString() {    return getClass().getName() + "@" + Integer.toHexString(hashCode());    }

生成的对象为EnhancerDemo$$EnhancerByCGLIB$$bc9b2066的实例, 这个类是运行时由cglib产生的