Spring MVC的处理器拦截器（HandlerInterceptor）类似于Servlet 规范中的过滤器Filter，用于对处理器进行预处理和后处理。
HandlerInterceptor 接口
package org.springframework.web.servlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.method.HandlerMethod;
public interface HandlerInterceptor {
/**
* 预处理回调方法
* true表示继续流程, false表示流程中断
*/
boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception;
/**
* 后处理回调方法，实现处理器的后处理（但在渲染视图之前），此时可以通过modelAndView对模型数据进行处理或对视图进行处理
*/
void postHandle(
HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
throws Exception;
/**
* 整个请求处理完毕回调方法，即在视图渲染完毕时回调
*/
void afterCompletion(
HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
throws Exception;
}
Spring MVC 提供了一个HandlerInterceptorAdapter 适配器类，让我们可以有选择的去实现感兴趣的方法，如下：
package org.springframework.web.servlet.handler;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.AsyncHandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
/**
* Abstract adapter class for the {@link AsyncHandlerInterceptor} interface,
* for simplified implementation of pre-only/post-only interceptors.
*
* @author Juergen Hoeller
* @since 05.12.2003
*/
public abstract class HandlerInterceptorAdapter implements AsyncHandlerInterceptor {
/**
* This implementation always returns {@code true}.
*/
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {
return true;
}
/**
* This implementation is empty.
*/
@Override
public void postHandle(
HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
throws Exception {
}
/**
* This implementation is empty.
*/
@Override
public void afterCompletion(
HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
throws Exception {
}
/**
* This implementation is empty.
*/
@Override
public void afterConcurrentHandlingStarted(
HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {
}
}
跟Netty4.1中的 ChannelInboundHandler和 ChannelInboundHandlerAdapter有异曲同工之妙。
使用
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">
<mvc:annotation-driven />
<context:component-scan base-package="com.bytebeats.springmvc.ch5.controller" >
<context:include-filter type="annotation" expression="org.springframework.stereotype.Controller" />
</context:component-scan>
<mvc:interceptors>
<mvc:interceptor>
<mvc:mapping path="/**" />
<bean class="com.bytebeats.springmvc.ch5.controller.interceptor.LogInterceptor" />
</mvc:interceptor>
<mvc:interceptor>
<mvc:mapping path="/api/**" />
<mvc:exclude-mapping path="/api/auth/login" />
<mvc:exclude-mapping path="/api/auth/register" />
<bean class="com.bytebeats.springmvc.ch5.controller.interceptor.AuthInterceptor" />
</mvc:interceptor>
</mvc:interceptors>
</beans>
LogInterceptor
import java.util.Set;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
public class LogInterceptor implements HandlerInterceptor{
private Logger logger = LoggerFactory.getLogger(LogInterceptor.class);
@Override
public boolean preHandle(HttpServletRequest request,
HttpServletResponse response, Object handler) throws Exception {
if(condition){
return false;
}
return true;
}
@Override
public void postHandle(HttpServletRequest request,
HttpServletResponse response, Object handler,
ModelAndView modelAndView) throws Exception {
}
@Override
public void afterCompletion(HttpServletRequest request,
HttpServletResponse response, Object handler, Exception ex)
throws Exception {
}
}
应用场景
- 日志记录：记录请求信息的日志，以便进行信息监控、信息统计、计算PV，trace跟踪 等。
- 权限检查：如登录检测，进入处理器检测检测是否登录，如果没有直接返回到登录页面；
- 性能监控：有时候系统在某段时间莫名其妙的慢，可以通过拦截器在进入处理器之前记录开始时间，在处理完后记；
关于 HandlerInterceptor 内部实现原理，下一篇文章中会详细介绍。
