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AOP（面向方面）的思想，就是把项目共同的那部分功能分离开来，比如日志记录，避免在业务逻辑里面夹杂着跟业务逻辑无关的代码。
下面是一个AOP实现的简单例子：
首先定义一些业务方法：
1 /** 2 * Created with IntelliJ IDEA. 3 * Author: wangjie email:tiantian.china.2@gmail.com 4 * Date: 13-9-23 5 * Time: 下午3:49 6 */ 7 public interface BussinessService { 8 public String login(String username, String password); 9 public String find(); 10 } 11 12 public class BussinessServiceImpl implements BussinessService { 13 private Logger logger = Logger.getLogger(this.getClass().getSimpleName()); 14 15 @Override 16 public String login(String username, String password) { 17 return "login success"; 18 } 19 20 @Override 21 public String find() { 22 return "find success"; 23 } 24 25 }
1 /** 2 * Created with IntelliJ IDEA. 3 * Author: wangjie email:tiantian.china.2@gmail.com 4 * Date: 13-9-24 5 * Time: 上午10:27 6 */ 7 public interface WorkService { 8 public String work(); 9 public String sleep(); 10 } 11 12 public class WorkServiceImpl implements WorkService{ 13 @Override 14 public String work() { 15 return "work success"; 16 } 17 18 @Override 19 public String sleep() { 20 return "sleep success"; 21 } 22 }
实现InvocationHandler接口，使用map来存储不同的InvocationHandler对象，避免生成过多。
1 package com.wangjie.aoptest2.invohandler; 2 3 import java.lang.reflect.InvocationHandler; 4 import java.lang.reflect.Method; 5 import java.lang.reflect.Proxy; 6 import java.util.Arrays; 7 import java.util.HashMap; 8 import java.util.logging.Logger; 9 10 /** 11 * Created with IntelliJ IDEA. 12 * Author: wangjie email:tiantian.china.2@gmail.com 13 * Date: 13-9-23 14 * Time: 下午3:47 15 */ 16 public class LogInvoHandler implements InvocationHandler{ 17 private Logger logger = Logger.getLogger(this.getClass().getSimpleName()); 18 19 private Object target; // 代理目标 20 private Object proxy; // 代理对象 21 22 private static HashMap<Class<?>, LogInvoHandler> invoHandlers = new HashMap<Class<?>, LogInvoHandler>(); 23 24 private LogInvoHandler() { 25 } 26 27 /** 28 * 通过Class来生成动态代理对象Proxy 29 * @param clazz 30 * @return 31 */ 32 public synchronized static<T> T getProxyInstance(Class<T> clazz){ 33 LogInvoHandler invoHandler = invoHandlers.get(clazz); 34 35 if(null == invoHandler){ 36 invoHandler = new LogInvoHandler(); 37 try { 38 T tar = clazz.newInstance(); 39 invoHandler.setTarget(tar); 40 invoHandler.setProxy(Proxy.newProxyInstance(tar.getClass().getClassLoader(), 41 tar.getClass().getInterfaces(), invoHandler)); 42 } catch (Exception e) { 43 e.printStackTrace(); 44 } 45 invoHandlers.put(clazz, invoHandler); 46 47 } 48 49 return (T)invoHandler.getProxy(); 50 } 51 52 @Override 53 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { 54 55 Object result = method.invoke(target, args); // 执行业务处理 56 57 // 打印日志 58 logger.info("____invoke method: " + method.getName() 59 + "; args: " + (null == args ? "null" : Arrays.asList(args).toString()) 60 + "; return: " + result); 61 62 63 return result; 64 } 65 66 public Object getTarget() { 67 return target; 68 } 69 70 public void setTarget(Object target) { 71 this.target = target; 72 } 73 74 public Object getProxy() { 75 return proxy; 76 } 77 78 public void setProxy(Object proxy) { 79 this.proxy = proxy; 80 } 81 }
然后编写一个Test类测试：
1 /** 2 * Created with IntelliJ IDEA. 3 * Author: wangjie email:tiantian.china.2@gmail.com 4 * Date: 13-9-24 5 * Time: 上午9:54 6 */ 7 public class Test { 8 public static Logger logger = Logger.getLogger(Test.class.getSimpleName()); 9 public static void main(String[] args) { 10 11 BussinessService bs = LogInvoHandler.getProxyInstance(BussinessServiceImpl.class); 12 bs.login("zhangsan", "123456"); 13 bs.find(); 14 15 logger.info("--------------------------------------"); 16 17 WorkService ws = LogInvoHandler.getProxyInstance(WorkServiceImpl.class); 18 ws.work(); 19 ws.sleep(); 20 21 logger.info("--------------------------------------"); 22 23 BussinessService bss = LogInvoHandler.getProxyInstance(BussinessServiceImpl.class); 24 bss.login("lisi", "654321"); 25 bss.find(); 26 27 } 28 }
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