上篇已经debug源码一步一步去了解了AOP是如何实现的,有兴趣的可以戳:
https://blog.csdn.net/qq_26975307/article/details/85116918
基于Spring的AOP简单实现
下面给出一个Spring AOP的.xml文件模板,名字叫做aop.xml,之后的内容都在aop.xml上进行扩展:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-4.2.xsd">
</beans>
注:
在讲解之前,说明一点:使用Spring AOP,要成功运行起代码,只用Spring提供给开发者的jar包是不够的,请下载两个jar包:
1、aopalliance.jar
2、aspectjweaver.jar
先定义一个接口:
public interface HelloWorld
{
void printHelloWorld();
void doPrint();
}
定义两个接口实现类:
public class HelloWorldImpl1 implements HelloWorld
{
public void printHelloWorld()
{
System.out.println("Enter HelloWorldImpl1.printHelloWorld()");
}
public void doPrint()
{
System.out.println("Enter HelloWorldImpl1.doPrint()");
return ;
}
}
public class HelloWorldImpl2 implements HelloWorld
{
public void printHelloWorld()
{
System.out.println("Enter HelloWorldImpl2.printHelloWorld()");
}
public void doPrint()
{
System.out.println("Enter HelloWorldImpl2.doPrint()");
return ;
}
}
横切关注点,这里是打印时间:
public class TimeHandler
{
public void printTime()
{
System.out.println("CurrentTime = " + System.currentTimeMillis());
}
}
有这三个类就可以实现一个简单的Spring AOP了,看一下aop.xml的配置:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-4.2.xsd">
<bean id="helloWorldImpl1" class="com.xrq.aop.HelloWorldImpl1" />
<bean id="helloWorldImpl2" class="com.xrq.aop.HelloWorldImpl2" />
<bean id="timeHandler" class="com.xrq.aop.TimeHandler" />
<aop:config>
<aop:aspect id="time" ref="timeHandler">
<aop:pointcut id="addAllMethod" expression="execution(* com.xrq.aop.HelloWorld.*(..))" />
<aop:before method="printTime" pointcut-ref="addAllMethod" />
<aop:after method="printTime" pointcut-ref="addAllMethod" />
</aop:aspect>
</aop:config>
</beans>
写一个main函数调用一下:
public static void main(String[] args)
{
ApplicationContext ctx =
new ClassPathXmlApplicationContext("aop.xml");
HelloWorld hw1 = (HelloWorld)ctx.getBean("helloWorldImpl1");
HelloWorld hw2 = (HelloWorld)ctx.getBean("helloWorldImpl2");
hw1.printHelloWorld();
System.out.println();
hw1.doPrint();
System.out.println();
hw2.printHelloWorld();
System.out.println();
hw2.doPrint();
}
看到给HelloWorld接口的两个实现类的所有方法都加上了代理,代理内容就是打印时间
CurrentTime = 1446129611993
Enter HelloWorldImpl1.printHelloWorld()
CurrentTime = 1446129611993
CurrentTime = 1446129611994
Enter HelloWorldImpl1.doPrint()
CurrentTime = 1446129611994
CurrentTime = 1446129611994
Enter HelloWorldImpl2.printHelloWorld()
CurrentTime = 1446129611994
CurrentTime = 1446129611994
Enter HelloWorldImpl2.doPrint()
CurrentTime = 1446129611994
基于Spring的AOP使用其他细节
1、增加一个横切关注点,打印日志,Java类为:
public class LogHandler
{
public void LogBefore()
{
System.out.println("Log before method");
}
public void LogAfter()
{
System.out.println("Log after method");
}
}
aop.xml配置为:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-4.2.xsd">
<bean id="helloWorldImpl1" class="com.xrq.aop.HelloWorldImpl1" />
<bean id="helloWorldImpl2" class="com.xrq.aop.HelloWorldImpl2" />
<bean id="timeHandler" class="com.xrq.aop.TimeHandler" />
<bean id="logHandler" class="com.xrq.aop.LogHandler" />
<aop:config>
<aop:aspect id="time" ref="timeHandler" order="1">
<aop:pointcut id="addTime" expression="execution(* com.xrq.aop.HelloWorld.*(..))" />
<aop:before method="printTime" pointcut-ref="addTime" />
<aop:after method="printTime" pointcut-ref="addTime" />
</aop:aspect>
<aop:aspect id="log" ref="logHandler" order="2">
<aop:pointcut id="printLog" expression="execution(* com.xrq.aop.HelloWorld.*(..))" />
<aop:before method="LogBefore" pointcut-ref="printLog" />
<aop:after method="LogAfter" pointcut-ref="printLog" />
</aop:aspect>
</aop:config>
</beans>
测试类不变,打印结果为:
CurrentTime = 1446130273734
Log before method
Enter HelloWorldImpl1.printHelloWorld()
Log after method
CurrentTime = 1446130273735
CurrentTime = 1446130273736
Log before method
Enter HelloWorldImpl1.doPrint()
Log after method
CurrentTime = 1446130273736
CurrentTime = 1446130273736
Log before method
Enter HelloWorldImpl2.printHelloWorld()
Log after method
CurrentTime = 1446130273736
CurrentTime = 1446130273737
Log before method
Enter HelloWorldImpl2.doPrint()
Log after method
CurrentTime = 1446130273737
要想让logHandler在timeHandler前使用有两个办法:
(1)aspect里面有一个order属性,order属性的数字就是横切关注点的顺序
(2)把logHandler定义在timeHandler前面,Spring默认以aspect的定义顺序作为织入顺序
2、我只想织入接口中的某些方法,修改一下pointcut的expression就好了:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-4.2.xsd">
<bean id="helloWorldImpl1" class="com.xrq.aop.HelloWorldImpl1" />
<bean id="helloWorldImpl2" class="com.xrq.aop.HelloWorldImpl2" />
<bean id="timeHandler" class="com.xrq.aop.TimeHandler" />
<bean id="logHandler" class="com.xrq.aop.LogHandler" />
<aop:config>
<aop:aspect id="time" ref="timeHandler" order="1">
<aop:pointcut id="addTime" expression="execution(* com.xrq.aop.HelloWorld.print*(..))" />
<aop:before method="printTime" pointcut-ref="addTime" />
<aop:after method="printTime" pointcut-ref="addTime" />
</aop:aspect>
<aop:aspect id="log" ref="logHandler" order="2">
<aop:pointcut id="printLog" expression="execution(* com.xrq.aop.HelloWorld.do*(..))" />
<aop:before method="LogBefore" pointcut-ref="printLog" />
<aop:after method="LogAfter" pointcut-ref="printLog" />
</aop:aspect>
</aop:config>
</beans>
表示timeHandler只会织入HelloWorld接口print开头的方法,logHandler只会织入HelloWorld接口do开头的方法
3、强制使用CGLIB生成代理
前面说过Spring使用动态代理或是CGLIB生成代理是有规则的,高版本的Spring会自动选择是使用动态代理还是CGLIB生成代理内容,当然我们也可以强制使用CGLIB生成代理,那就是<aop:config>里面有一个"proxy-target-class"属性,这个属性值如果被设置为true,那么基于类的代理将起作用,如果proxy-target-class被设置为false或者这个属性被省略,那么基于接口的代理将起作用。