Spring AOP(Aspect-oriented programming) 是用于切面编程,简单的来说:AOP相当于一个拦截器,去拦截一些处理,例如:当一个方法执行的时候,Spring 能够拦截正在执行的方法,在方法执行的前或者后增加额外的功能和处理。
在Spring AOP中支持4中类型的通知:
1:before advice 在方法执行前执行。
2:after returning advice 在方法执行后返回一个结果后执行。
3:after throwing advice 在方法执行过程中抛出异常的时候执行。
4:Around advice 在方法执行前后和抛出异常时执行,相当于综合了以上三种通知。
下面是一个简单的AOP advice 的例子:
首先给出一个简单的Spring 注入的例子,
定义一个Book类:
[java]
package com.myapp.core.aop.advice;
public class Book {
private String name;
private String url;
private int pages;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public int getPages() {
return pages;
}
public void setPages(int pages) {
this.pages = pages;
}
public void printName(){
System.out.println("Book name "+ this.name);
}
public void printUrl(){
System.out.println("Book URL "+this.url);
}
public void printThrowException(){
throw new IllegalArgumentException();
}
}
相应的配置文件:
[html]
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<!-- more bean definitions for data access objects go here -->
<bean id="book" class="com.myapp.core.aop.advice.Book">
<property name="name" value="Effective java" />
<property name="url" value="www.google.cn"/>
<property name="pages" value="300" />
</bean>
</beans>
对应的测试类:
[java]
package com.myapp.core.aop.advice;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainTest {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("resource/aop.xml");
Book book = (Book) context.getBean("book");
System.out.println("---------------------");
book.printName();
System.out.println("---------------------");
book.printUrl();
System.out.println("----------------------");
try{
book.printThrowException();
}catch(Exception e){
// e.printStackTrace();
}
}
}
输出结果:
[plain]
三月 20, 2013 11:01:01 上午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@11e831: startup date [Wed Mar 20 11:01:01 CST 2013]; root of context hierarchy
三月 20, 2013 11:01:01 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [resource/aop.xml]
三月 20, 2013 11:01:01 上午 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@13b5500: defining beans [book]; root of factory hierarchy
---------------------
Book name Effective java
---------------------
Book URL www.google.cn
----------------------
下面对以上的Book加上Spring AOP advices
1:before advice
before advice将在方法执行前执行,创建一个实现MethodBeforeAdvice接口的类能够定义执行方法前的操作。
类如下:
[java]
package com.myapp.core.aop.advice;
import java.lang.reflect.Method;
import org.springframework.aop.MethodBeforeAdvice;
public class BeforeMethod implements MethodBeforeAdvice {
@Override