Spring's AOP learning

usage

Based on notes

• Configuration

@Configuration
@EnableAspectJAutoProxy
public class AppConfig {

}

• section

  Section: that class connection point and our point of tangency and notice where our section called

package org.xyz;
import org.aspectj.lang.annotation.Aspect;

@Aspect
@component
public class NotVeryUsefulAspect {

}

• Cut-off point

  Set tangent point, connection point: Pointcut

  Pointcut: connection point, the spring AOP, the minimum unit is called the point of attachment methods, each method we call a method, an expression can be expressed as a plurality of connection points, a plurality of connection points together termed as the cutoff point.

  Notice: @ before, @ after and so on, cut into the cut point of the timing and content of the Leads points.

package com.xyz.someapp;

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

@Aspect
@component
public class SystemArchitecture {

    /
     * A join point is in the web layer if the method is defined
     * in a type in the com.xyz.someapp.web package or any sub-package
     * under that.
     /
    @Pointcut("within(com.xyz.someapp.web..)")
    public void inWebLayer() {}

    /
     * A join point is in the service layer if the method is defined
     * in a type in the com.xyz.someapp.service package or any sub-package
     * under that.
     /
    @Pointcut("within(com.xyz.someapp.service..)")
    public void inServiceLayer() {}

    /
     * A join point is in the data access layer if the method is defined
     * in a type in the com.xyz.someapp.dao package or any sub-package
     * under that.
     /
    @Pointcut("within(com.xyz.someapp.dao..)")
    public void inDataAccessLayer() {}

    /
     * A business service is the execution of any method defined on a service
     * interface. This definition assumes that interfaces are placed in the
     * "service" package, and that implementation types are in sub-packages.
     *
     * If you group service interfaces by functional area (for example,
     * in packages com.xyz.someapp.abc.service and com.xyz.someapp.def.service) then
     * the pointcut expression "execution(* com.xyz.someapp..service..(..))"
     * could be used instead.
     *
     * Alternatively, you can write the expression using the 'bean'
     * PCD, like so "bean(Service)". (This assumes that you have
     * named your Spring service beans in a consistent fashion.)
     */
    @Pointcut("execution( com.xyz.someapp..service..(..))")
    public void businessService() {}

    /*
     * A data access operation is the execution of any method defined on a
     * dao interface. This definition assumes that interfaces are placed in the
     * "dao" package, and that implementation types are in sub-packages.
     */
    @Pointcut("execution( com.xyz.someapp.dao..(..))")
    public void dataAccessOperation() {}

}

xml-based

• Configuration

<aop:aspectj-autoproxy/>

• section

<bean id="myAspect" class="org.xyz.NotVeryUsefulAspect">
    <!-- configure properties of the aspect here -->
</bean>

• Cut-off point

<aop:config>
    <aop:advisor
        pointcut="com.xyz.someapp.SystemArchitecture.businessService()"
        advice-ref="tx-advice"/>
</aop:config>

<tx:advice id="tx-advice">
    <tx:attributes>
        <tx:method name="*" propagation="REQUIRED"/>
    </tx:attributes>
</tx:advice>

Pointcut expression Keywords:

　   1）execution：用于匹配子表达式。

            //匹配com.cjm.model包及其子包中所有类中的所有方法，返回类型任意，方法参数任意
            @Pointcut("execution(* com.cjm.model..*.*(..))")
            public void before(){}

 

      2）within：用于匹配连接点所在的Java类或者包。

            //匹配Person类中的所有方法
            @Pointcut("within(com.cjm.model.Person)")
            public void before(){}

 

            //匹配com.cjm包及其子包中所有类中的所有方法

            @Pointcut("within(com.cjm..*)")
            public void before(){}

 

     3） this：用于向通知方法中传入代理对象的引用。
            @Before("before() && this(proxy)")
            public void beforeAdvide(JoinPoint point, Object proxy){
                  //处理逻辑
            }

 

      4）target：用于向通知方法中传入目标对象的引用。
            @Before("before() && target(target)
            public void beforeAdvide(JoinPoint point, Object proxy){
                  //处理逻辑
            }

 

      5）args：用于将参数传入到通知方法中。
            @Before("before() && args(age,username)")
            public void beforeAdvide(JoinPoint point, int age, String username){
                  //处理逻辑
            }
 
      6）@within ：用于匹配在类一级使用了参数确定的注解的类，其所有方法都将被匹配。 

            @Pointcut("@within(com.cjm.annotation.AdviceAnnotation)") － 所有被@AdviceAnnotation标注的类都将匹配
            public void before(){}

　　

      7）@target ：和@within的功能类似，但必须要指定注解接口的保留策略为RUNTIME。
            @Pointcut("@target(com.cjm.annotation.AdviceAnnotation)")
            public void before(){}

 

      8）@args ：传入连接点的对象对应的Java类必须被@args指定的Annotation注解标注。
            @Before("@args(com.cjm.annotation.AdviceAnnotation)")
            public void beforeAdvide(JoinPoint point){
                  //处理逻辑
            }

　　

      9）@annotation ：匹配连接点被它参数指定的Annotation注解的方法。也就是说，所有被指定注解标注的方法都将匹配。
            @Pointcut("@annotation(com.cjm.annotation.AdviceAnnotation)")
            public void before(){}

      10）bean：通过受管Bean的名字来限定连接点所在的Bean。该关键词是Spring2.5新增的。
            @Pointcut("bean(person)")
            public void before(){}

Spring aop complete principle: not the time getbean of the target object is converted into a proxy object, but when initialization by calling the spring of BeanPostProcessors, create a proxy object, stored in singletonObjects this map collection.