上一篇的Spring AOP Advice例子中，Class（CustomerService）中的全部method都被自动的拦截了。但是大多情况下，你只需要去拦截一两个method。这样就引入了Pointcut（切入点）的概念，它允许你根据method的名字去拦截指定的method。另外，一个Pointcut必须结合一个Advisor来使用。
在Spring AOP中，有3个常用的概念:
- Advices：表示一个method执行前或执行后的动作。
- Pointcut：表示根据method的名字或者正则表达式去拦截一个method。
- Advisor：Advice和Pointcut组成的独立的单元，并且能够传给proxy factory 对象。
一、回顾Around advice
1、在CustomerService.java中
package com.zhangyu.customer.services;
public class CustomerService {
private String name;
private String occupation;
public void setName(String name) { this.name = name;}
public void printName() {System.out.println("Customer name : " + this.name);}
public void printOccupation() {System.out.println("Customer occupation : " + this.occupation);}
public void setOccupation(String occupation) {this.occupation = occupation;}
public void printThrowException() {
throw new IllegalArgumentException();
}
}
2、 在HelloAroundMethod.java中
package com.zhangyu.aop;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
public class HelloAroundMethod implements MethodInterceptor {
@Override
public Object invoke(MethodInvocation methodInvocation) throws Throwable {
System.out.println("Method name : " + methodInvocation.getMethod().getName());
// same with MethodBeforeAdvice
System.out.println("HelloAroundMethod : Before method ,hello");
try {
Object result = methodInvocation.proceed();
// same with AfterReturningAdvice
System.out.println("HelloAroundMethod : Before after ,hello!");
return result;
} catch (IllegalArgumentException e) {
// same with ThrowsAdvice
System.out.println("HelloAroundMethod : Throw exception ,hello!");
throw e;
}
}
}
3、 在Spring-Customer.xml中
<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.zhangyu.customer.services.CustomerService">
<property name="name" value="Zhang Yu" />
<property name="occupation" value="developer" />
</bean>
<bean id="helloAroundMethodBean" class="com.zhangyu.aop.HelloAroundMethod" />
<bean id="customerServiceProxy" class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="target" ref="customerService" />
<property name="interceptorNames">
<list>
<value>helloAroundMethodBean</value>
</list>
</property>
</bean>
</beans>
4、运行，在App.java中
package com.zhangyu.common;
import com.zhangyu.customer.services.CustomerService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class App {
public static void main(String[] args) {
ApplicationContext appContext = new ClassPathXmlApplicationContext(
new String[] { "Spring-Customer.xml" });
CustomerService cust = (CustomerService) appContext
.getBean("customerService");
System.out.println("*************************");
cust.printName();
System.out.println("*************************");
cust.printOccupation();
System.out.println("*************************");
try {
cust.printThrowException();
} catch (Exception e) {
}
}
}
5、运行结果
*************************
Method name : printName
HelloAroundMethod : Before method ,hello!
Customer name : Zhang Yu
HelloAroundMethod : After method ,hello!
*************************
Method name : printOccupation
HelloAroundMethod : Before method ,hello!
Customer occupation : developer
HelloAroundMethod : After method ,hello!
*************************
Method name : printThrowException
HelloAroundMethod : Before method ,hello!
HelloAroundMethod : Throw exception ,hello!
二、Pointcut
可以用名字匹配法和正则表达式匹配法去匹配要拦截的method。
1、Pointcut——名字匹配法
（1）通过pointcut和advisor拦截printName()方法。
* 创建一个NameMatchMethodPointcut的bean，将你想拦截的方法的名字printName注入到属性mappedName。 * 创建一个DefaultPointcutAdvisor的advisor bean，将pointcut和advice关联起来。 * 更改代理的interceptorNames的value值为customerAdvisor。
<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.zhangyu.customer.services.CustomerService">
<property name="name" value="Zhang Yu" />
<property name="occupation" value="developer" />
</bean>
<bean id="helloAroundMethodBean" class="com.zhangyu.aop.HelloAroundMethod" />
<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="customerPointcut" class="org.springframework.aop.support.NameMatchMethodPointcut">
<property name="mappedName" value="printName" />
</bean>
<bean id="customerAdvisor" class="org.springframework.aop.support.DefaultPointcutAdvisor">
<property name="pointcut" ref="customerPointcut" />
<property name="advice" ref="helloAroundMethodBean" />
</bean>
</beans>
#####（2）运行，结果如下：
*************************
Method name : printName
HelloAroundMethod : Before method ,hello!
Customer name : Zhang Yu
HelloAroundMethod : After method ,hello!
*************************
Customer occupation : developer
*************************
可以看到，只拦截了printName（），在其前后分别输出了”Before method ，hello!”和”After method ,hello!”
#####（3）另外 以上配置中pointcut和advisor可以合并在一起配置，即不用单独配置customerPointcut和customerAdvisor，只要配置customerAdvisor时class选择NameMatchMethodPointcutAdvisor如下：
<bean id="customerAdvisor" class="org.springframework.aop.support.NameMatchMethodPointcutAdvisor">
<property name="mappedName" value="printName" />
<property name="advice" ref="helloAroundMethodBean" />
</bean>
但是，如果将method名字单独配置成pointcut（切入点），advice和pointcut的结合会更灵活，使一个pointcut可以和多个advice结合，更符合松耦合理念。
2、Pointcut——正则表达式匹配法
(1) 你可以配置用正则表达式匹配需要拦截的method：
<bean id="customerAdvisor" class="org.springframework.aop.support.RegexpMethodPointcutAdvisor">
<property name="patterns">
<list>
<value>.*Occu.*</value>
</list>
</property>
<property name="advice" ref="helloAroundMethodBean" />
</bean>
(2) 结果
*************************
Customer name : Zhang Yu
*************************
Method name : printOccupation
HelloAroundMethod : Before method ,hello!
Customer occupation : developer
HelloAroundMethod : After method ,hello!
*************************
可以看到，拦截名字中包含了Occu字符的method，这里是printOccupation()。