Spring3系列10- Spring AOP——Pointcut，Advisor拦截指定方法

时间：2021-11-19 09:08:58

Spring3系列10- Spring AOP——Pointcut，Advisor

　　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，你只需要一个方法去拦截一两个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、Pointcut、Advisor，解释如下，

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。

下边来回顾一下上一篇例子中的代码

CustomerService.java

package com.lei.demo.aop.advice;

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();

    }

}

配置文件Spring-AOP-Advice.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.lei.demo.aop.advice.CustomerService">

        <property name="name" value="LeiOOLei" />

        <property name="url" value="http://www.cnblogs.com/leiOOlei/" />

    </bean>

    <bean id="hijackAroundMethodBean" class="com.lei.demo.aop.advice.HijackAroundMethod" />

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

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

        <property name="interceptorNames">

            <list>

                <value>hijackAroundMethodBean</value>

            </list>

        </property>

    </bean>

</beans>

HijackAroundMethod.java

package com.lei.demo.aop.advice;

import java.util.Arrays;

import org.aopalliance.intercept.MethodInterceptor;

import org.aopalliance.intercept.MethodInvocation;

public class HijackAroundMethod implements MethodInterceptor {

    public Object invoke(MethodInvocation methodInvocation) throws Throwable {

        System.out.println("Method name : "

                + methodInvocation.getMethod().getName());

        System.out.println("Method arguments : "

                + Arrays.toString(methodInvocation.getArguments()));

        // 相当于  MethodBeforeAdvice

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

        try {

            // 调用原方法，即调用CustomerService中的方法

            Object result = methodInvocation.proceed();

            // 相当于 AfterReturningAdvice

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

            return result;

        } catch (IllegalArgumentException e) {

            // 相当于 ThrowsAdvice

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

            throw e;

        }

    }

}

运行如下App.java

package com.lei.demo.aop.advice;

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-AOP-Advice.xml" });

        System.out.println("使用Spring AOP 如下");

        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) {

        }

    }

}

运行结果：

使用Spring AOP 如下

*************************

Method name : printName

Method arguments : []

HijackAroundMethod : Before method hijacked!

Customer name : LeiOOLei

HijackAroundMethod : After method hijacked!

*************************

Method name : printURL

Method arguments : []

HijackAroundMethod : Before method hijacked!

Customer website : http://www.cnblogs.com/leiOOlei/

HijackAroundMethod : After method hijacked!

*************************

Method name : printThrowException

Method arguments : []

HijackAroundMethod : Before method hijacked!

HijackAroundMethod : Throw exception hijacked!

上边的结果中，CustomerService.java中，全部的method方法全部被拦截了，下边我们将展示怎样利用Pointcuts只拦截printName()。

你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——Name match example

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，如下

<bean id="customerPointcut"

        class="org.springframework.aop.support.NameMatchMethodPointcut">

        <property name="mappedName" value="printName" />

</bean>

创建一个DefaultPointcutAdvisor的advisor bean，将pointcut和advice关联起来。

<bean id="customerAdvisor"

        class="org.springframework.aop.support.DefaultPointcutAdvisor">

        <property name="pointcut" ref="customerPointcut" />

        <property name="advice" ref=" hijackAroundMethodBean " />

</bean>

更改代理的interceptorNames值，将上边的advisor（ customerAdvisor）替代原来的hijackAroundMethodBean。

<bean id="customerServiceProxy"

        class="org.springframework.aop.framework.ProxyFactoryBean">

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

        <property name="interceptorNames">

            <list>

                <value>customerAdvisor</value>

            </list>

        </property>

</bean>

所有的配置文件如下：

<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.lei.demo.aop.advice.CustomerService">

        <property name="name" value="LeiOOLei" />

        <property name="url" value="http://www.cnblogs.com/leiOOlei/" />

    </bean>

    <bean id="hijackAroundMethodBean" class="com.lei.demo.aop.advice.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="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=" hijackAroundMethodBean " />

    </bean>

</beans>

再运行一下App.java，输出结果如下：

使用Spring AOP 如下

*************************

Method name : printName

Method arguments : []

HijackAroundMethod : Before method hijacked!

Customer name : LeiOOLei

HijackAroundMethod : After method hijacked!

*************************

Customer website : http://www.cnblogs.com/leiOOlei/

*************************

以上运行结果显示，只拦截了printName()方法。

注意：

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="hijackAroundMethodBean" />

</bean>

这样，整个配置文件如下：

<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.lei.demo.aop.advice.CustomerService">

        <property name="name" value="LeiOOLei" />

        <property name="url" value="http://www.cnblogs.com/leiOOlei/" />

    </bean>

    <bean id="hijackAroundMethodBean" class="com.lei.demo.aop.advice.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="customerAdvisor" class="org.springframework.aop.support.NameMatchMethodPointcutAdvisor">

        <property name="mappedName" value="printName" />

        <property name="advice" ref="hijackAroundMethodBean" />

    </bean>

</beans>

　　实际上这种做法将method名字与具体的advice捆绑在一起，有悖于Spring松耦合理念，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。

2.      Pointcut——Regular exxpression match example

你可以配置用正则表达式匹配需要拦截的method，如下配置

<bean id="customerAdvisor" class="org.springframework.aop.support.RegexpMethodPointcutAdvisor">

        <property name="patterns">

            <list>

                <value>.*URL.*</value>

            </list>

        </property>

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

    </bean>

现在，你可以拦截名字中包含URL字符的method了，在实际工作中，你可以用它来管理DAO层，例如，你可以用“.*DAO.*”来拦截所有DAO层中的相关业务。

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