下面来介绍 4 种类型的通知（Advice）。
Before Advice
method 运行前，将运行下面的代码。
HijackBeforeMethod.java 如下:
package com.shiyanlou.spring.aop.advice;
import java.lang.reflect.Method;
import org.springframework.aop.MethodBeforeAdvice;
public class HijackBeforeMethod implements MethodBeforeAdvice {
public void before(Method arg0, Object[] args, Object target)
throws Throwable {
System.out.println("HijackBeforeMethod : Before method hijacked!");
}
}
在配置文件中加入新的 bean 配置 HijackBeforeMethod，然后创建一个新的代理（proxy），命名为 customerServiceProxy。target 定义你想劫持哪个 bean；interceptorNames 定义想用哪个 class(advice) 劫持 target。ApringAOPAdvice.xml 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.xsd">
<bean id = "customerService" class = "com.shiyanlou.spring.aop.advice.CustomerService">
<property name = "name" value = "Shiyanlou" />
<property name = "url" value = "https://www.lanqiao.cn" />
</bean>
<bean id = "hijackBeforeMethodBean" class = "com.shiyanlou.spring.aop.advice.HijackBeforeMethod" />
<bean id = "customerServiceProxy" class = "org.springframework.aop.framework.ProxyFactoryBean">
<property name = "target" ref = "customerService" />
<property name = "interceptorNames">
<list>
<value>hijackBeforeMethodBean</value>
</list>
</property>
</bean>
</beans>
用 Spring proxy 之前，必须添加 CGLIB 类库，在之前的 pom.xml 文件中，已经添加到了其中，以下是 pom.xml 依赖：
<dependency>
<groupId>cglib</groupId>
<artifactId>cglib</artifactId>
<version>3.2.9</version>
</dependency>
App.java 如下：
package com.shiyanlou.spring.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[] { "SpringAOPAdvice.xml" });
CustomerService cust = (CustomerService) appContext.getBean("customerServiceProxy");
System.out.println("使用Spring AOP 如下");
System.out.println("*************************");
cust.printName();
System.out.println("*************************");
cust.printURL();
System.out.println("*************************");
try {
cust.printThrowException();
} catch (Exception e) {
}
}
}
输入命令:
mvn compile
mvn exec:java -Dexec.mainClass="com.shiyanlou.spring.aop.advice.App"
实验结果如下：
每一个 customerService 的 method 运行前，都将先执行 HijackBeforeMethod 的 before 方法。
After Returning Advice
创建一个实现了接口 AfterReturningAdvice 的 class，method 运行后，直到返回结果后，才运行下边的代码，如果没有返回结果，将不运行切入的代码。
HijackAfterMethod.java 如下：
package com.shiyanlou.spring.aop.advice;
import java.lang.reflect.Method;
import org.springframework.aop.AfterReturningAdvice;
public class HijackAfterMethod implements AfterReturningAdvice {
public void afterReturning(Object returnValue, Method method, Object[] args, Object target) throws Throwable {
System.out.println("HijackAfterMethod : After method hijacked!");
}
}
修改 bean 配置文件，加入 hijackAfterMethodBean 配置，ApringAOPAdvice.xml 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.xsd">
<bean id = "customerService" class = "com.shiyanlou.spring.aop.advice.CustomerService">
<property name = "name" value = "lanqiao" />
<property name = "url" value = "lanqiao.cn" />
</bean>
<bean id = "hijackBeforeMethodBean" class = "com.shiyanlou.spring.aop.advice.HijackBeforeMethod" />
<bean id = "hijackAfterMethodBean" class = "com.shiyanlou.spring.aop.advice.HijackAfterMethod" />
<bean id = "customerServiceProxy" class = "org.springframework.aop.framework.ProxyFactoryBean">
<property name = "target" ref = "customerService" />
<property name = "interceptorNames">
<list>
<value>hijackAfterMethodBean</value>
</list>
</property>
</bean>
</beans>
现在再运行 App.java 后输出如下：
每一个 customerService 的 method 运行后，都将先执行 HijackAfterMethod 的 afterReturning 方法。
After Throwing Advice
创建一个实现了 ThrowsAdvice 接口的 class，劫持 IllegalArgumentException 异常，目标 method 运行时，抛出 IllegalArgumentException 异常后，运行切入的方法。HijackThrowExceptionMethod.java 如下：
package com.shiyanlou.spring.aop.advice;
import org.springframework.aop.ThrowsAdvice;
public class HijackThrowExceptionMethod implements ThrowsAdvice {
public void afterThrowing(IllegalArgumentException e) throws Throwable {
System.out.println("HijackThrowException : Throw exception hijacked!");
}
}
修改 bean 配置文件，加入了 hijackThrowExceptionBean，ApringAOPAdvice.xml 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.xsd">
<bean id = "customerService" class = "com.shiyanlou.spring.aop.advice.CustomerService">
<property name = "name" value = "lanqiao" />
<property name = "url" value = "lanqiao.cn" />
</bean>
<bean id = "hijackBeforeMethodBean" class = "com.shiyanlou.spring.aop.advice.HijackBeforeMethod" />
<bean id = "hijackAfterMethodBean" class = "com.shiyanlou.spring.aop.advice.HijackAfterMethod" />
<bean id = "hijackThrowExceptionBean" class = "com.shiyanlou.spring.aop.advice.HijackThrowExceptionMethod" />
<bean id = "customerServiceProxy" class = "org.springframework.aop.framework.ProxyFactoryBean">
<property name = "target" ref = "customerService" />
<property name = "interceptorNames">
<list>
<value>hijackThrowExceptionBean</value>
</list>
</property>
</bean>
</beans>
运行结果如下：
Around Advice
结合了以上 3 种形式的 Advice，创建一个实现了接口 MethodInterceptor 的 class，你必须通过 methodInvocation.proceed() 来调用原来的方法，即通过调用 methodInvocation.proceed() 来调用 CustomerService 中的每一个方法，当然也可以不调用原方法 HijackAroundMethod.java 如下：
package com.shiyanlou.spring.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;
}
}
}
修改 bean 配置文件，加入了 hijackAroundMethodBean，ApringAOPAdvice.xml 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.xsd">
<bean id = "customerService" class = "com.shiyanlou.spring.aop.advice.CustomerService">
<property name = "name" value = "lanqiao" />
<property name = "url" value = "lanqiao.cn" />
</bean>
<bean id = "hijackBeforeMethodBean" class = "com.shiyanlou.spring.aop.advice.HijackBeforeMethod" />
<bean id = "hijackAfterMethodBean" class = "com.shiyanlou.spring.aop.advice.HijackAfterMethod" />
<bean id = "hijackThrowExceptionBean" class = "com.shiyanlou.spring.aop.advice.HijackThrowExceptionMethod" />
<bean id = "hijackAroundMethodBean" class = "com.shiyanlou.spring.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>
运行结果：
