一、Spring AOP的简单实例

1. 往pom.xml文件添加以下依赖：

<dependency>
  <groupId>org.testng</groupId>
  <artifactId>testng</artifactId>
  <version>6.4</version>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-context</artifactId>
  <version>3.1.2.RELEASE</version>
</dependency>
<dependency>
  <groupId>cglib</groupId>
  <artifactId>cglib</artifactId>
  <version>2.2.2</version>
</dependency>
<dependency>
  <groupId>org.aspectj</groupId>
  <artifactId>aspectjweaver</artifactId>
  <version>1.7.0</version>
</dependency>

2. 在src/main/resources目录下新建spring-aop.xml文件：

<?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"
  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"
  default-autowire="byName">

  <bean id="aspect" class="com.john.spring.aop.MyAspect" />
  
  <bean id="grace" class="com.john.spring.aop.Graceful" />
  
  <aop:config proxy-target-class="true">
  	<aop:aspect ref="aspect">
  		<aop:before pointcut="execution(* com.john..Graceful.analogous())" method="beforeAdvice()" />
  	</aop:aspect>
  </aop:config>
</beans>

3. MyAspect切面类：

public class MyAspect {
    public void beforeAdvice() {
        System.out.println("beforeAdvice() is executed!");
    }
}

4. Graceful目标类：

public class Graceful {
    public void analogous() {
        System.out.println("Analogous() is being executed");
    }
}

5. BeforeAdviceTest测试类：

public class BeforeAdviceTest {
	@Test
	public void test() {
		AbstractApplicationContext ctx = new ClassPathXmlApplicationContext("beans-aop.xml");
		Graceful graceful = ctx.getBean("grace", Graceful.class);
		graceful.analogous();
	}
}

运行test()方法，输出：

beforeAdvice() is executed!
Analogous() is being executed


附：
①. <aop:config>需要添加proxy-target-class="true"属性，防止使用JDK代理导致在获取实例并转换为Graceful时报错。

②. 不管是目标类还是切面类，都要交由spring托管，并委托CGLIB改写目标类。