AOP 入门

1，源码

Application.java

package com.bf;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import java.util.List;
import java.util.Date;
import java.util.Iterator; 

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

@SuppressWarnings("unused")
public class Application {

      public static void main(String[] args) {
          try{
              ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

              SpitterDAO dao = (SpitterDAO)context.getBean("dao");

              dao.SaveEvent();
          }catch (Throwable ex) {
             throw new ExceptionInInitializerError(ex);
          }
      }
    }

Audience.java

package com.bf;

public class Audience {
    public void takeSeats()
    {
        System.out.println("sit down");

    }
}

ApplicationContext.xml

<?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:p="http://www.springframework.org/schema/p"
    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-3.0.xsd
    http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
    http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">

    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
        <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver" />
        <property name="url" value="" />
        <property name="username" value="" />
        <property name="password" value="" />
    </bean>
    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <constructor-arg ref="dataSource" />
    </bean>
    <bean id="dao" class="com.bf.JDBCDAO" autowire="byName">
        <property name="jdbcTemplate" ref="jdbcTemplate" />
    </bean>
    <bean id="Audience" class="com.bf.Audience" autowire="byName">
    </bean>

       <bean id="sessionFactory" class="org.springframework.orm.hibernate5.LocalSessionFactoryBean">
        <property name="dataSource">
            <ref bean="dataSource" />
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">
                    org.hibernate.dialect.Oracle9Dialect
                </prop>
            </props>
        </property>
        <property name="mappingResources">
            <list>
                <value>Event.hbm.xml</value>
            </list>
        </property>
    </bean>
    <bean id="transactionManager" class="org.springframework.orm.hibernate5.HibernateTransactionManager">
        <property name="sessionFactory">
            <ref bean="sessionFactory" />
        </property>
    </bean>

    <aop:config>
        <aop:aspect ref="Audience">
            <aop:before pointcut="execution(* com.bf.SpitterDAO.SaveEvent(..))" method="takeSeats" />
        </aop:aspect>
    </aop:config>
</beans>

需要的Jar列表

spring-aop-4.2.3.RELEASE.jar
spring-beans-4.2.3.RELEASE.jar
spring-context-4.2.3.RELEASE.jar"
spring-context-support-4.2.3.RELEASE.jar
spring-core-4.2.3.RELEASE.jar
spring-expression-4.2.3.RELEASE.jar
commons-logging.jar
spring-jdbc-4.2.3.RELEASE.jar"
spring-tx-4.2.3.RELEASE.jar
commons-dbcp-1.2.jar
commons-pool-1.2.jar
ojdbc14.jar
commons-collections-3.1.jar
antlr-2.7.7.jar
classmate-1.3.0.jar
dom4j-1.6.1.jar
geronimo-jta_1.1_spec-1.1.1.jar
hibernate-commons-annotations-5.0.1.Final.jar
hibernate-core-5.1.0.Final.jar
hibernate-jpa-2.1-api-1.0.0.Final.jar
jandex-2.0.0.Final.jar
javassist-3.20.0-GA.jar
jboss-logging-3.3.0.Final.jar
spring-orm-4.2.3.RELEASE.jar
aopalliance.jar
spring-aspects-4.2.3.RELEASE.jar
aspectj-weaver.jar

演示在SaveEvent前调Audience.takeSeats().

注意SpitterDAO dao = (SpitterDAO)context.getBean("dao"); 这里用的是接口而不是实现类。

也可以如下配置切面

    <aop:config>
        <aop:aspect ref="Audience">
            <aop:pointcut id="seat" expression="execution(* com.bf.SpitterDAO.SaveEvent(..))" ></aop:pointcut>
            <aop:before pointcut-ref="seat" method="takeSeats" />
        </aop:aspect>
    </aop:config>

2,基本概念

切面Aspect

通知和切点的结合，两者共同定义了关于切面的全部内容。

通知Advice

定义了切面的“什么”和“何时”。切面的“工作”被称为通知。

连接点JoinPoint

连接点是Application运行过程中能够插入切面的一个点。这个点可以是方法调用时、抛出异常时、甚至修改一个字段时。

切点Pointcut

定义了切面的“何处”，切点的定义会匹配通知要织入的一个或多个连接点。Pointcuts pick out join points.

参考资料：http://www.eclipse.org/aspectj/doc/released/progguide/language-joinPoints.html