Enhancer允许为非接口类型创建一个Java代理。Enhancer动态创建了给定类型的子类但是拦截了所有的方法。和Proxy不一样的是，不管是接口还是类他都能正常工作。

来个场景模拟一下AOP

package cglib.enhancer;public class Hello {public String sayHello(boolean throwException) throws Exception {System.out.println("hello everyone!");if(throwException)throw new Exception("test exception");return "123";}
}

ProxyFactory用于创建增强代理实现了方法拦截

package cglib.enhancer;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 ProxyFactory implements MethodInterceptor {//要代理的原始对象private Object obj;public Object createProxy(Object target) {this.obj = target;Enhancer enhancer = new Enhancer();enhancer.setSuperclass(this.obj.getClass());// 设置代理目标enhancer.setCallback(this);// 设置回调enhancer.setClassLoader(target.getClass().getClassLoader());return enhancer.create();}@Overridepublic Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {Object result = null;try {// 前置通知before();result = proxy.invokeSuper(obj, args);// 后置通知after();} catch (Exception e) {exception();}finally{beforeReturning();}return result;}private void before() {System.out.println("before method invoke");}private void after() {System.out.println("after method invoke");}private void exception() {System.out.println("method invoke exception");}private void beforeReturning() {System.out.println("before returning");}
}

package cglib.enhancer;public class EnhancerTest {public static void main(String[] args) throws Exception {Hello hello = new Hello();ProxyFactory cglibProxy = new ProxyFactory();Hello proxy = (Hello) cglibProxy.createProxy(hello);String result=proxy.sayHello(true);System.out.println(result);}
}

before method invoke
hello everyone!
method invoke exception
before returning
null

before method invoke
hello everyone!
after method invoke
before returning
123

package net.sf.cglib.proxy;/*** All callback interfaces used by {@link Enhancer} extend this interface.* @see MethodInterceptor* @see NoOp* @see LazyLoader* @see Dispatcher* @see InvocationHandler* @see FixedValue*/
public interface Callback
{
}

接口都很简单。

先来一个基础POJO类：

public class SampleClass {public String test(String input) {return "Hello world!";}
}

FixedValue 

@Test
public void testFixedValue() throws Exception {Enhancer enhancer = new Enhancer();enhancer.setSuperclass(SampleClass.class);enhancer.setCallback(new FixedValue() {@Overridepublic Object loadObject() throws Exception {return "Hello cglib!";}});SampleClass proxy = (SampleClass) enhancer.create();assertEquals("Hello cglib!", proxy.test(null));
}

InvocationHandler

@Test
public void testInvocationHandler() throws Exception {Enhancer enhancer = new Enhancer();enhancer.setSuperclass(SampleClass.class);enhancer.setCallback(new InvocationHandler() {@Overridepublic Object invoke(Object proxy, Method method, Object[] args)throws Throwable {if(method.getDeclaringClass() != Object.class && method.getReturnType() == String.class) {return "Hello cglib!";} else {throw new RuntimeException("Do not know what to do.");}}});SampleClass proxy = (SampleClass) enhancer.create();assertEquals("Hello cglib!", proxy.test(null));assertNotEquals("Hello cglib!", proxy.toString());
}

@Test
public void testMethodInterceptor() throws Exception {Enhancer enhancer = new Enhancer();enhancer.setSuperclass(SampleClass.class);enhancer.setCallback(new MethodInterceptor() {@Overridepublic Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy)throws Throwable {if(method.getDeclaringClass() != Object.class && method.getReturnType() == String.class) {return "Hello cglib!";} else {return proxy.invokeSuper(obj, args);}}});SampleClass proxy = (SampleClass) enhancer.create();assertEquals("Hello cglib!", proxy.test(null));assertNotEquals("Hello cglib!", proxy.toString());proxy.hashCode(); // Does not throw an exception or result in an endless loop.
}

Dispatcher

ProxyRefDispatcher

NoOp