标题：Spring AOP实例(Pointcut,Advisor)

在上一个Spring AOP通知的例子，一个类的整个方法被自动拦截。但在大多数情况下，可能只需要一种方式来拦截一个或两个方法，这就是为什么引入'切入点'的原因。它允许你通过它的方法名来拦截方法。另外，一个“切入点”必须具有“Advisor' 相关联。

在Spring AOP中，有三个非常专业术语- Advices, Yiibaicut , Advisor，把它在非官方的方式...

• Advice – 指示之前或方法执行后采取的行动。
• Yiibaicut – 指明哪些方法应该拦截，通过方法的名称或正则表达式模式。
• Advisor – 分组"通知"和”切入点“成为一个单元，并把它传递到代理工厂对象。

再次回顾上一个 Spring AOP通知的例子。

File : CustomerService.java

package com.yiibai.customer.services;

public class CustomerService
{
	private String name;
	private String url;

	public void setName(String name) {
		this.name = name;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	public void printName(){
		System.out.println("Customer name : " + this.name);
	}
	
	public void printURL(){
		System.out.println("Customer website : " + this.url);
	}
	
	public void printThrowException(){
		throw new IllegalArgumentException();
	}
	
}

File : applicationContext.xml

<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-2.5.xsd">

	<bean id="customerService" class="com.yiibai.customer.services.CustomerService">
		<property name="name" value="Yong Mook Kim" />
		<property name="url" value="http://www.yiibai.com" />
	</bean>

	<bean id="hijackAroundMethodBeanAdvice" class="com.yiibai.aop.HijackAroundMethod" />

	<bean id="customerServiceProxy" 
                class="org.springframework.aop.framework.ProxyFactoryBean">

		<property name="target" ref="customerService" />

		<property name="interceptorNames">
			<list>
				<value>hijackAroundMethodBeanAdvice</value>
			</list>
		</property>
	</bean>
</beans>

File : HijackAroundMethod.java

package com.yiibai.aop;

import java.util.Arrays;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

public class HijackAroundMethod implements MethodInterceptor {
	@Override
	public Object invoke(MethodInvocation methodInvocation) throws Throwable {

		System.out.println("Method name : "
				+ methodInvocation.getMethod().getName());
		System.out.println("Method arguments : "
				+ Arrays.toString(methodInvocation.getArguments()));

		System.out.println("HijackAroundMethod : Before method hijacked!");

		try {
			Object result = methodInvocation.proceed();
			System.out.println("HijackAroundMethod : Before after hijacked!");

			return result;

		} catch (IllegalArgumentException e) {

			System.out.println("HijackAroundMethod : Throw exception hijacked!");
			throw e;
		}
	}
}

执行它

package com.yiibai.common;

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

import com.yiibai.customer.services.CustomerService;

public class App {
	public static void main(String[] args) {
		ApplicationContext appContext = new ClassPathXmlApplicationContext(
				new String[] { "applicationContext.xml" });

		CustomerService cust = (CustomerService) appContext
				.getBean("customerServiceProxy");

		System.out.println("*************************");
		cust.printName();
		System.out.println("*************************");
		cust.printURL();
		System.out.println("*************************");
		try {
			cust.printThrowException();
		} catch (Exception e) {
		}
	}
}

输出

*************************
Method name : printName
Method arguments : []
HijackAroundMethod : Before method hijacked!
Customer name : Yiibai
HijackAroundMethod : Before after hijacked!
*************************
Method name : printURL
Method arguments : []
HijackAroundMethod : Before method hijacked!
Customer website : http://www.yiibai.com
HijackAroundMethod : Before after hijacked!
*************************
Method name : printThrowException
Method arguments : []
HijackAroundMethod : Before method hijacked!
HijackAroundMethod : Throw exception hijacked!

客户服务类的全部方法被截获。后来，我们展示如何使用“切入点”只拦截printName()方法。

切入点的例子

可以通过以下两种方式相匹配的方法：

1. 名称匹配
2. 正则表达式匹配

1.切入点 - 名称匹配的例子

通过“切入点”和“advisor”拦截printName()方法。创建NameMatchMethodYiibaicut切入点bean，并提出要在“mappedName”属性值来拦截方法名。

<bean id="customerYiibaicut"
        class="org.springframework.aop.support.NameMatchMethodYiibaicut">
		<property name="mappedName" value="printName" />
	</bean>

创建 DefaultYiibaicutAdvisor 通知 bean，通知和切入点相关联。

<bean id="customerAdvisor"
		class="org.springframework.aop.support.DefaultYiibaicutAdvisor">
		<property name="pointcut" ref="customerYiibaicut" />
		<property name="advice" ref="hijackAroundMethodBeanAdvice" />
	</bean>

更换代理“interceptorNames”到“customerAdvisor”（它是“hijackAroundMethodBeanAdvice”）。

<bean id="customerServiceProxy"
		class="org.springframework.aop.framework.ProxyFactoryBean">

		<property name="target" ref="customerService" />
		
		<property name="interceptorNames">
			<list>
				<value>customerAdvisor</value>
			</list>
		</property>
	</bean>

全部bean配置文件

<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-2.5.xsd">

	<bean id="customerService" class="com.yiibai.customer.services.CustomerService">
		<property name="name" value="Yiibai" />
		<property name="url" value="http://www.yiibai.com" />
	</bean>

	<bean id="hijackAroundMethodBeanAdvice" class="com.yiibai.aop.HijackAroundMethod" />

	<bean id="customerServiceProxy" 
                class="org.springframework.aop.framework.ProxyFactoryBean">

		<property name="target" ref="customerService" />

		<property name="interceptorNames">
			<list>
				<value>customerAdvisor</value>
			</list>
		</property>
	</bean>

	<bean id="customerYiibaicut" 
                class="org.springframework.aop.support.NameMatchMethodYiibaicut">
		<property name="mappedName" value="printName" />
	</bean>

	<bean id="customerAdvisor" 
                 class="org.springframework.aop.support.DefaultYiibaicutAdvisor">
		<property name="pointcut" ref="customerYiibaicut" />
		<property name="advice" ref="hijackAroundMethodBeanAdvice" />
	</bean>

</beans>

再次运行，输出

*************************
Method name : printName
Method arguments : []
HijackAroundMethod : Before method hijacked!
Customer name : Yiibai
HijackAroundMethod : Before after hijacked!
*************************
Customer website : http://www.yiibai.com
*************************

现在，只拦截 printName()方法。

YiibaicutAdvisor

Spring提供了YiibaicutAdvisor类来保存工作声明advisor和切入点到不同的bean，可以使用 NameMatchMethodYiibaicutAdvisor 两者结合成一个 bean。

<bean id="customerAdvisor"
		class="org.springframework.aop.support.NameMatchMethodYiibaicutAdvisor">
	
		<property name="mappedName" value="printName" />
		<property name="advice" ref="hijackAroundMethodBeanAdvice" />
	
	</bean>

2.切入点 - 正则表达式的例子

也可以通过使用正则表达式匹配切入点方法的名称  – RegexpMethodYiibaicutAdvisor.

<bean id="customerAdvisor"
		class="org.springframework.aop.support.RegexpMethodYiibaicutAdvisor">
		<property name="patterns">
			<list>
				<value>.*URL.*</value>
			</list>
		</property>

		<property name="advice" ref="hijackAroundMethodBeanAdvice" />
	</bean> 

现在，它拦截方法名称中有“URL”的方法。在实践中，可以用它来管理DAO层，声明“.*DAO.*” 拦截所有的DAO类来支持事务。

下载代码 – http://pan.baidu.com/s/1pJU2PoJ