下面是一个AOP实现的简单例子：

首先定义一些业务方法：

复制代码 代码如下:
/**
* Created with IntelliJ IDEA.
* Author: wangjie email:tiantian.china.2@gmail.com
* Date: 13-9-23
* Time: 下午3:49
*/
public interface BussinessService {
public String login(String username, String password);
public String find();
}

public class BussinessServiceImpl implements BussinessService {
private Logger logger = Logger.getLogger(this.getClass().getSimpleName());

@Override
public String login(String username, String password) {
return "login success";
}

@Override
public String find() {
return "find success";
}

}

复制代码 代码如下:
/**
* Created with IntelliJ IDEA.
* Author: wangjie email:tiantian.china.2@gmail.com
* Date: 13-9-24
* Time: 上午10:27
*/
public interface WorkService {
public String work();
public String sleep();
}

public class WorkServiceImpl implements WorkService{
@Override
public String work() {
return "work success";
}

@Override
public String sleep() {
return "sleep success";
}
}

实现InvocationHandler接口，使用map来存储不同的InvocationHandler对象，避免生成过多。

复制代码 代码如下:
package com.wangjie.aoptest2.invohandler;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.HashMap;
import java.util.logging.Logger;

/**
* Created with IntelliJ IDEA.
* Author: wangjie email:tiantian.china.2@gmail.com
* Date: 13-9-23
* Time: 下午3:47
*/
public class LogInvoHandler implements InvocationHandler{
private Logger logger = Logger.getLogger(this.getClass().getSimpleName());

private Object target; // 代理目标
private Object proxy; // 代理对象

private static HashMap<Class<?>, LogInvoHandler> invoHandlers = new HashMap<Class<?>, LogInvoHandler>();

private LogInvoHandler() {
}

/**
* 通过Class来生成动态代理对象Proxy
* @param clazz
* @return
*/
public synchronized static<T> T getProxyInstance(Class<T> clazz){
LogInvoHandler invoHandler = invoHandlers.get(clazz);

if(null == invoHandler){
invoHandler = new LogInvoHandler();
try {
T tar = clazz.newInstance();
invoHandler.setTarget(tar);
invoHandler.setProxy(Proxy.newProxyInstance(tar.getClass().getClassLoader(),
tar.getClass().getInterfaces(), invoHandler));
} catch (Exception e) {
e.printStackTrace();
}
invoHandlers.put(clazz, invoHandler);

}

return (T)invoHandler.getProxy();
}

@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

Object result = method.invoke(target, args); // 执行业务处理

// 打印日志
logger.info("____invoke method: " + method.getName()
+ "; args: " + (null == args ? "null" : Arrays.asList(args).toString())
+ "; return: " + result);

return result;
}

public Object getTarget() {
return target;
}

public void setTarget(Object target) {
this.target = target;
}

public Object getProxy() {
return proxy;
}

public void setProxy(Object proxy) {
this.proxy = proxy;
}
}

然后编写一个Test类测试：

复制代码 代码如下:
/**
* Created with IntelliJ IDEA.
* Author: wangjie email:tiantian.china.2@gmail.com
* Date: 13-9-24
* Time: 上午9:54
*/
public class Test {
public static Logger logger = Logger.getLogger(Test.class.getSimpleName());
public static void main(String[] args) {

BussinessService bs = LogInvoHandler.getProxyInstance(BussinessServiceImpl.class);
bs.login("zhangsan", "123456");
bs.find();

logger.info("--------------------------------------");

WorkService ws = LogInvoHandler.getProxyInstance(WorkServiceImpl.class);
ws.work();
ws.sleep();

logger.info("--------------------------------------");

BussinessService bss = LogInvoHandler.getProxyInstance(BussinessServiceImpl.class);
bss.login("lisi", "654321");
bss.find();

}
}

以后需要添加新的业务逻辑XXXService，只需要调用

XXXService xs = LogInvoHandler.getProxyInstance(XXXServiceImpl.class);

即可。

也可以模仿Spring等框架的配置，把bean的类名配置在xml文件中，如：

<bean id="bussinessService" class="com.wangjie.aoptest2.service.impl.BussinessServiceImpl">

然后在java代码中解析xml，通过Class.forName("com.wangjie.aoptest2.service.impl.BussinessServiceImpl");获得Class对象

然后通过LogInvoHandler.getProxyInstance(Class.forName("com.wangjie.aoptest2.service.impl.BussinessServiceImpl"));获得代理对象Proxy

再使用反射去调用代理对象的方法。

运行结果如下：

九月 24, 2013 11:08:03 上午 com.wangjie.aoptest2.invohandler.LogInvoHandler invoke
INFO: ____invoke method: login; args: [zhangsan, 123456]; return: login success
九月 24, 2013 11:08:03 上午 com.wangjie.aoptest2.invohandler.LogInvoHandler invoke
INFO: ____invoke method: find; args: null; return: find success
九月 24, 2013 11:08:03 上午 com.wangjie.aoptest2.Test main
INFO: --------------------------------------
九月 24, 2013 11:08:03 上午 com.wangjie.aoptest2.invohandler.LogInvoHandler invoke
INFO: ____invoke method: work; args: null; return: work success
九月 24, 2013 11:08:03 上午 com.wangjie.aoptest2.invohandler.LogInvoHandler invoke
INFO: ____invoke method: sleep; args: null; return: sleep success
九月 24, 2013 11:08:03 上午 com.wangjie.aoptest2.Test main
INFO: --------------------------------------
九月 24, 2013 11:08:03 上午 com.wangjie.aoptest2.invohandler.LogInvoHandler invoke
INFO: ____invoke method: login; args: [lisi, 654321]; return: login success
九月 24, 2013 11:08:03 上午 com.wangjie.aoptest2.invohandler.LogInvoHandler invoke
INFO: ____invoke method: find; args: null; return: find success