AOP的基本思想
AOP的意思是面向方面编程，英文全称：AspectOriented Programming；AOP能够降低代码的耦合性，使得代码易于维护和重（chong）用,一个应用程序分为核心关注点和横切关注点。核心关注点和具体应用的功能相关，而横切关注点存在于整个系统的范围内。Spring的AOP是建立在Java的代理机制之上的。
Java的代理机制
通用的日志输出方法
============TimeBook类==============
package com.gc.action.book;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
public class TimeBook {
private Logger logger = Logger.getLogger(this.getClass().getName());
public void doAuditing(String name){
System.out.println(logger);
logger.log(Level.INFO,name +"开始。。。");
System.out.println("=================");
logger.log(Level.INFO,name +"结束。。。");
}
}
=============TestTimeBook类============
package com.gc.action.book;
public class TestTimeBook {
public static void main(String[] args) {
TimeBook timeBook = new TimeBook();
timeBook.doAuditing("zx");
}
}
========log4j.properties 配置文件===================
# Set root category priority to INFO and its only appender to CONSOLE.
log4j.rootCategory=INFO, CONSOLE
#log4j.rootCategory=INFO, CONSOLE, LOGFILE
# Set the enterprise logger category to FATAL and its only appender to CONSOLE.
log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE
# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.Threshold=INFO
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=- %m%n
# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=axis.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.Threshold=INFO
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n
==================结果===============
org.apache.log4j.Logger@1ddc4ec2
- zx开始。。。
=================
- zx结束。。。
通过面向接口编程实现日志输出
============接口TimeBookInterface类====================
package com.gc.action.impl;
public interface TimeBookInterface {
//通过面向接口编程实现日志输出
public void doAuditing(String name);
}
============接口实现TimeBookImpl类=======================
package com.gc.action.impl;
public class TimeBookImpl implements TimeBookInterface {
@Override
public void doAuditing(String name) {
System.out.println(name+"实现");
}
}
===========日志输出类TimeBookProxy =========================
package com.gc.action.impl;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
/**
* 日志输出
* @author yltd
*
*/
public class TimeBookProxy {
private Logger logger = Logger.getLogger(this.getClass().getName());
private TimeBookInterface timeBookInterface;
public TimeBookProxy(TimeBookInterface timeBookInterface){
this.timeBookInterface = timeBookInterface;
}
/**
* 实际业务处理
*/
public void doAuditing(String name){
logger.log(Level.INFO, name+" 开始审批。");
timeBookInterface.doAuditing(name);
logger.log(Level.INFO, name+" 审批结束。");
}
}
==============测试类TestTimeBook ================================
package com.gc.action.impl;
public class TestTimeBook {
public static void main(String[] args) {
TimeBookProxy timeBookProxy = new TimeBookProxy(new TimeBookImpl());
timeBookProxy.doAuditing("zyx");
}
}
================结果======================
- zyx 开始审批。
zyx实现
- zyx 审批结束。
使用Java的代理机制实现日志输出
====接口TestLogInterface =========================
package com.gc.action.javaLog;
/**
* 接口
* @author yltd
*
*/
public interface TestLogInterface {
//操作方法
public void doSameing(String name);
}
========实现类TestLogImpl ========================
package com.gc.action.javaLog;
/**
* 实现类
* @author yltd
*
*/
public class TestLogImpl implements TestLogInterface {
@Override
public void doSameing(String name) {
System.out.println("name = "+name);
}
}
============日志信息代理类LogProxy ====================
package com.gc.action.javaLog;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
/**
* 日志信息的代理类
* @author yltd
*
*/
public class LogProxy implements InvocationHandler{
private Logger logger =Logger.getLogger(this.getClass().getName());
private Object obj;
public Object dind(Object obj){
this.obj=obj;
return Proxy.newProxyInstance(obj.getClass().getClassLoader(), obj.getClass().getInterfaces(),this);
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Object result =null;
logger.log(Level.INFO, args[0]+" 开始。。。");
result = method.invoke(obj, args);
logger.log(Level.INFO, args[0]+" 结束。。。");
return result;
}
}
============测试类TestMain ===========================
package com.gc.action.javaLog;
/**
* 测试类
* @author yltd
*
*/
import com.gc.action.javaLog.TestLogInterface;
public class TestMain {
public static void main(String[] args) {
LogProxy lp =new LogProxy();
TestLogInterface tli =(TestLogInterface) lp.dind(new TestLogImpl());
tli.doSameing("zyx");
}
}
==========结果============
- zyx 开始。。。
name = zyx
- zyx 结束。。。
总结：第一种方式，需要在每个类里都增加对输出日志信息的代码；第二种方式，虽然实现了业务逻辑与输出日志信息代码的分离，但还是必须依赖于固定的接口；第三种方式，真正实现了对输出日志信息代码的重用，并且不依赖于固定的接口实现。
