java spring 拦截 spring实现拦截器

1.自定义被拦截的接口，且实现接口。

代码:

package demo;
public interface UserService //被拦截的接口
{
 public void printUser(String user);
}


package demo;
public class UserServiceImp extends UserService //实现UserService接口
{
  public void printUser(String user)
  {
   System.out.println("printUser user:"+user);//显示user 
  }
}

2 实现AOP的方法级拦截器。它可以在目标操作前后执行，拦截自定义接口的参数，或拦截接口返回的值。

代码:

package demo;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

public class UserInterceptor implements MethodInterceptor
       //AOP方法拦截器
       {

    public Object invoke(MethodInvocation arg0) throws Throwable {
    
        try {
            
            if (arg0.getMethod().getName().equals("printUser"))
              //拦截方法是否是UserService接口的printUser方法 
            {
                 Object[] args = arg0.getArguments();//被拦截的参数
                 System.out.println("user:"+args[0]);
                 arg0.getArguments()[0]="hello!" //修改被拦截的参数
                
                
            }
            
            System.out.println(arg0.getMethod().getName() + "---!");
                        return arg0.proceed();//运行UserService接口的printUser方法

        } catch (Exception e) {
            throw e;
        }
    }

3. ApplicationContext.xml的设置

<?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
   
   <beans>
    <bean id="userServiceImp" class="demo.UserServiceImp”>
   </bean>
   
 
  
  <bean id="userInterceptor" class="demo.UserInterceptor">
  </bean>
  
 
  
  <bean id="userService" 
      class="org.springframework.aop.framework.ProxyFactoryBean">
      <property name="proxyInterfaces"><value>demo.UserService</value></property>
  
      <property name="target"><ref local="userServiceImp"/></property>
      <property name="interceptorNames">
          <list>
              <value>userInterceptor</value>
          </list>
      </property>
  </bean>
  
 </beans>

4.运行

package demo;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.support.FileSystemXmlApplicationContext;
 
 public class DemoApp
 {
  public static void main(String[] args)
  {
         ApplicationContext ac = new FileSystemXmlApplicationContext(
                "classpath:ApplicationContext.xml");
    UserService us = (UserService) ac.getBean("userService");
     String user="zhao";

     us.printUser("zhao");

  }
 }

 运行结果：

 [java]  user:zhao

 [java]  printUser user:hello!