在上一個(gè)Spring AOP通知的例子，一個(gè)類的整個(gè)方法被自動(dòng)攔截。但在大多數(shù)情況下，可能只需要一種方式來攔截一個(gè)或兩個(gè)方法，這就是為什么引入'切入點(diǎn)'的原因。它允許你通過它的方法名來攔截方法。另外，一個(gè)“切入點(diǎn)”必須具有“Advisor' 相關(guān)聯(lián)。

在Spring AOP中，有三個(gè)非常專業(yè)術(shù)語- Advices, Yiibaicut , Advisor，把它在非官方的方式...

Advice – 指示之前或方法執(zhí)行后采取的行動(dòng)。
Yiibaicut – 指明哪些方法應(yīng)該攔截，通過方法的名稱或正則表達(dá)式模式。
Advisor – 分組"通知"和”切入點(diǎn)“成為一個(gè)單元，并把它傳遞到代理工廠對(duì)象。

再次回顧上一個(gè) 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;
		}
	}
}

執(zhí)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) {
		}
	}
}

輸出

*************************
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!

客戶服務(wù)類的全部方法被截獲。后來，我們展示如何使用“切入點(diǎn)”只攔截printName()方法。

切入點(diǎn)的例子

可以通過以下兩種方式相匹配的方法：

名稱匹配
正則表達(dá)式匹配

1.切入點(diǎn) - 名稱匹配的例子

通過“切入點(diǎn)”和“advisor”攔截printName()方法。創(chuàng)建NameMatchMethodYiibaicut切入點(diǎn)bean，并提出要在“mappedName”屬性值來攔截方法名。

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

創(chuàng)建 DefaultYiibaicutAdvisor 通知 bean，通知和切入點(diǎn)相關(guān)聯(lián)。

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

更換代理“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>

再次運(yùn)行，輸出

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

現(xiàn)在，只攔截 printName()方法。

YiibaicutAdvisor

Spring提供了YiibaicutAdvisor類來保存工作聲明advisor和切入點(diǎn)到不同的bean，可以使用 NameMatchMethodYiibaicutAdvisor 兩者結(jié)合成一個(gè) bean。

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

2.切入點(diǎn) - 正則表達(dá)式的例子

也可以通過使用正則表達(dá)式匹配切入點(diǎn)方法的名稱 – 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>

現(xiàn)在，它攔截方法名稱中有“URL”的方法。在實(shí)踐中，可以用它來管理DAO層，聲明“.*DAO.*” 攔截所有的DAO類來支持事務(wù)。

下載代碼 – http://pan.baidu.com/s/1pJU2PoJ

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