java使用動態代理來實現AOP（日誌記錄）

如下內容爲原創，轉載時請註明連接地址：http://www.cnblogs.com/tiantianbyconan/p/3336627.html

AOP（面向方面）的思想，就是把項目共同的那部分功能分離開來，好比日誌記錄，避免在業務邏輯裏面夾雜着跟業務邏輯無關的代碼。

下面是一個AOP實現的簡單例子：

首先定義一些業務方法：

 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 }

實現InvocationHandler接口，使用map來存儲不一樣的InvocationHandler對象，避免生成過多。

 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; // 代理目標
20     private Object proxy; // 代理對象
21 
22     private static HashMap<Class<?>, LogInvoHandler> invoHandlers = new HashMap<Class<?>, LogInvoHandler>();
23 
24     private LogInvoHandler() {
25     }
26 
27     /**
28      * 經過Class來生成動態代理對象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); // 執行業務處理
56 
57         // 打印日誌
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 }

 

而後編寫一個Test類測試：

 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 }

之後須要添加新的業務邏輯XXXService，只須要調用

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

便可。

也能夠模仿Spring等框架的配置，把bean的類名配置在xml文件中，如：

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

而後在java代碼中解析xml，經過Class.forName("com.wangjie.aoptest2.service.impl.BussinessServiceImpl");得到Class對象

而後經過LogInvoHandler.getProxyInstance(Class.forName("com.wangjie.aoptest2.service.impl.BussinessServiceImpl"));得到代理對象Proxy

再使用反射去調用代理對象的方法。

 

運行結果以下：

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