读书笔记-基于注解和声明式的aop

@AspectJ配置切面

编程方式实现

public class Waiter {
    public void check(String name){
        System.out.println("waiter说:结帐?"+name);
    }
    public void serve(String name){
        System.out.println("waiter说:要点什么?"+name);
    }
}

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;

@Aspect
public class PreGreeting {
    @Before("execution(* serve(..))")
    public void beforeGreeting(){
        System.out.println("how are you!");
    }
}

@Before注解表示前置加强,后面的切点表达式表示在目标类的serve()方法织入加强，serve()方法能够带任意的传入参数和任意的返回值。
PreGreeting类经过注解，将切点，加强类型和加强的横切逻辑组合在一块儿。PreGreeting类至关于上一篇中的BeforeAdvice(加强),NameMatchMethodPointcut(切点)，DefaultPointcutAdvisor(切面)三者联合表达的信息。

Waiter waiter=new Waiter();
        AspectJProxyFactory factory=new AspectJProxyFactory();
        factory.setTarget(waiter);//设置目标类
        factory.addAspect(PreGreeting.class);//添加切面
        Waiter proxy=factory.getProxy();
        proxy.serve("TheViper");
        proxy.check("TheViper");

how are you!
waiter说:要点什么?TheViper
waiter说:结帐?TheViper

经过配置使用

<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:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
    http://www.springframework.org/schema/beans/spring-beans.xsd 
    http://www.springframework.org/schema/aop 
    http://www.springframework.org/schema/aop/spring-aop.xsd">
    <aop:aspectj-autoproxy/>
    <bean id='waiter' class='aspectj.Waiter'/>
    <bean class='aspectj.PreGreeting'/>
</beans>

• 引用aop命名空间

xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="...  
    http://www.springframework.org/schema/aop 
    http://www.springframework.org/schema/aop/spring-aop.xsd"

• <aop:aspectj-autoproxy/>自动为spring容器中那些匹配@AspectJ切面的Bean建立代理，完成切面织入

ApplicationContext ctx=new ClassPathXmlApplicationContext("beans.xml");
        Waiter waiter=(Waiter)ctx.getBean("waiter");
        waiter.serve("TheViper");
        waiter.check("TheViper");

使用的时候，直接获取bean操做就能够了，不用像前面还要建立AspectJProxyFactory,设置好代理才能用。

schema配置切面

配置命名切点

须要引入aspectjweaver

public class GreetBefore {
    public void say(String name){
        System.out.println("hallo!"+name);
    }
}

加强不用像上一篇中那样，须要继承特定类或实现特定接口。

<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:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
    http://www.springframework.org/schema/beans/spring-beans.xsd 
    http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">
    <bean id='waiterTarget' class='com.Waiter'/>
    <bean id='greetBefore' class='schema.GreetBefore'/>
    <aop:config>
        <aop:pointcut expression="target(com.Waiter) and execution(* check(..)) and args(name,..)" 
        id="servePointcut"/>
        <aop:aspect ref="greetBefore">
            <aop:before method="say" pointcut-ref="servePointcut"/>
        </aop:aspect>
    </aop:config>
</beans>

匹配Waiter类中的check()方法。

• 须要引入aop命名空间

xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="... http://www.springframework.org/schema/aop 
http://www.springframework.org/schema/aop/spring-aop.xsd"

• <aop:aspect>定义切面，其内部能够定义多个加强,ref属性指定引用的具体加强

• <aop:before>声明了一个前置加强，经过pointcut-ref属性引用切点,method属性指定加强中哪一个方法用于具体的加强行为

• <aop:pointcut>定义切点，expression属性设置切点表达式，其语法和@AspectJ中的语法彻底相同。

public class Waiter {
    public void check(String name){
        System.out.println("waiter说:结帐?"+name);
    }
    public void serve(String name){
        System.out.println("waiter说:要点什么?"+name);
    }
}

ApplicationContext ctx=new ClassPathXmlApplicationContext("applicationContext.xml");
        Waiter waiter=(Waiter)ctx.getBean("waiterTarget");
        waiter.serve("TheViper");
        waiter.check("TheViper");

waiter说:要点什么?TheViper
hallo!TheViper
waiter说:结帐?TheViper

配置顺序问题

命名切点只能被当前<aop:aspect>内定义的元素访问到，<aop:config>中的配置顺序必须是<aop:pointcut>=><aop:advisor>=><aop:aspect>

各类加强类型

后置加强

<aop:config>
    ...
    <aop:aspect ref="greetBefore">
        <aop:after-returning method="sayEnjoy" pointcut='target(com.Waiter) and execution(* serve(..))'/>
    </aop:aspect>
</aop:config>

环绕加强

<aop:config>
    ...
    <aop:aspect ref="greetBefore">
        <aop:around method="aroundMethod" pointcut='execution(* serve(..)) and within(com.Waiter))'/>
    </aop:aspect>
</aop:config>

public void aroundMethod(ProceedingJoinPoint pjp){
    //pjp能够访问到环绕加强的链接点信息
        ...
    }

抛出异常加强

<aop:config>
    ...
    <aop:aspect ref="greetBefore">
        <aop:after-throwing method="afterThrowingMethod" pointcut='target(com.Waiter) and 
        execution(* serve(..))' throwing='exception'/>
    </aop:aspect>
</aop:config>

public void afterThrowingMethod(Exception exception){
    ...
}

throwing属性声明须要绑定的异常对象，指定的异常名必须和加强方法对应的传入参数一致

final加强

<aop:config>
    ...
    <aop:aspect ref="greetBefore">
        <aop:after method="afterMethod" pointcut='execution(*com.Waiter. serve(..))'/>
    </aop:aspect>
</aop:config>

引介加强