轉(zhuǎn)載地址：http://kentkwan.iteye.com/blog/739499

面向切面編程（AOP）實(shí)現(xiàn)了從另一個(gè)層面解決了面向?qū)ο笏荒芙鉀Q的對(duì)象間耦合度問題。今天閑來無聊做了個(gè)模擬AOP的小例子，有不完善的地方請(qǐng)指出。

首先我們定義一個(gè)接口和實(shí)現(xiàn)類

package com.gzmu.dynamic.PRoxy.service;import java.io.Serializable;import com.gzmu.dynamic.proxy.po.User;public interface UserService {void saveUser(User user);void updateUser(User user);void deleteUser(User user);    User getUser(Serializable id);}
package com.gzmu.dynamic.proxy.service.impl;import java.io.Serializable;import com.gzmu.dynamic.proxy.po.User;import com.gzmu.dynamic.proxy.service.UserService;public class UserServiceImpl implements UserService {    @Overridepublic void saveUser(User user) {        System.out.println("save user success!");    }    @Overridepublic void deleteUser(User user) {        System.out.println("delete user success!");    }    @Overridepublic User getUser(Serializable id) {        System.out.println("get user success!");return null;    }    @Overridepublic void updateUser(User user) {        System.out.println("update user success!");    }}
然后我們建立一個(gè)對(duì)UserService方法的攔截器。
package com.gzmu.dynamic.proxy.interceptor;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import com.gzmu.dynamic.proxy.service.impl.UserServiceImpl;public class UserServiceInterceptor implements InvocationHandler {private Object targer;private String methodName;private BeforeInterceptor beforeInterceptor;private AfterInterceptor afterInterceptor;public UserServiceInterceptor(Object targer, String methodName) {this.targer = targer;this.methodName = methodName;    }public void setBeforeInterceptor(BeforeInterceptor beforeInterceptor) {if (this.beforeInterceptor == null)this.beforeInterceptor = beforeInterceptor;    }public void setAfterInterceptor(AfterInterceptor afterInterceptor) {if (this.afterInterceptor == null)this.afterInterceptor = afterInterceptor;    }    @Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {if (method.getName().equals(methodName)) {            execute(beforeInterceptor);            Object o = method.invoke(new UserServiceImpl(), args);            execute(afterInterceptor);return o;        }return method.invoke(targer, args);    }private void execute(Interceptor interceptor) {if (interceptor != null)            interceptor.execute();    }}
因?yàn)槲覀兿脒@個(gè)攔截器可以攔截到方法的調(diào)用，并且可以在方法的調(diào)用前后執(zhí)行額外可以指定的操作，所以我們使用三個(gè)接口來實(shí)現(xiàn)這個(gè)功能。
package com.gzmu.dynamic.proxy.interceptor;public interface Interceptor {void execute();}// --------------------------------------------------------------package com.gzmu.dynamic.proxy.interceptor;public interface BeforeInterceptor extends Interceptor  {}// --------------------------------------------------------------package com.gzmu.dynamic.proxy.interceptor;public interface AfterInterceptor extends Interceptor {}
最后組裝我們的攔截器來實(shí)現(xiàn)AOP操作
package com.gzmu.dynamic.proxy.test;import java.lang.reflect.Proxy;import org.junit.Test;import com.gzmu.dynamic.proxy.interceptor.AfterInterceptor;import com.gzmu.dynamic.proxy.interceptor.BeforeInterceptor;import com.gzmu.dynamic.proxy.interceptor.UserServiceInterceptor;import com.gzmu.dynamic.proxy.po.User;import com.gzmu.dynamic.proxy.service.UserService;import com.gzmu.dynamic.proxy.service.impl.UserServiceImpl;public class TestCase {    @Testpublic void test() {        UserServiceInterceptor interceptor = new UserServiceInterceptor(new UserServiceImpl(), "saveUser");        interceptor.setBeforeInterceptor(new BeforeInterceptor() {            @Overridepublic void execute() {                System.out.println("before saveUser...");            }        });        interceptor.setAfterInterceptor(new AfterInterceptor() {            @Overridepublic void execute() {                System.out.println("after saveUser...");            }        });        UserService serivce = (UserService) Proxy.newProxyInstance(getClass().getClassLoader(), new Class[] { UserService.class }, interceptor);        serivce.saveUser(new User());        serivce.updateUser(new User());        serivce.deleteUser(new User());        serivce.getUser(null);    }}
運(yùn)行結(jié)果如下
before saveUser...save user success!after saveUser...update user success!delete user success!get user success!怎么樣，超爽吧，再也不用重復(fù)的編寫同樣的代碼了，而且能然代碼組織得更加有邏輯。