关于Spring MVC的HandlerInterceptor

最新推荐文章于 2025-01-02 15:22:47 发布

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本文深入探讨了Spring MVC框架中拦截器（HandlerInterceptor）的工作原理，包括其三个核心方法preHandle、postHandle和afterCompletion的功能及执行流程。通过实例演示了多个拦截器的顺序执行与逆序回调机制，以及在不同场景下的应用效果。

HandlerInterceptor有三个需要实现的方法

package Interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyFirstInterceptor implements HandlerInterceptor {


    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("我是预处理");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("我是后处理");
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("请求处理完毕，视图已渲染，开始最终处理");
    }
}

可以有多个处理器拦截器，preHandle方法的执行是顺序的，postHandle，afterCompletion方法是逆序的。

preHandle：在请求到达处理器之前执行的

postHandle：在处理器处理完请求之后，渲染视图之前执行的

afterCompletion：触发整个请求处理完毕回调方法afterCompletion

当preHandle方法返回true时，会接着执行下个拦截器的prehandle方法。

正常流程

1.preHandle方法都返回true，顺序执行

2.然后由处理器处理请求

3.逆序调用拦截器的postHandle方法

4.进行视图渲染

5.最后逆序执行afterCompletion方法

非正常流程

执行HandlerInterceptor3的preHandle方法返回true，接着执行HandlerInterceptor4的preHandle方法，返回false

此时中断流程，直接逆序执行preHandle返回true的拦截器的afterCompletion方法，中间流程都直接跳过不执行！！！

自己写的测试程序

spring-mvc.xml

<?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:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
       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/aop
     http://www.springframework.org/schema/aop/spring-aop.xsd
     http://www.springframework.org/schema/tx
     http://www.springframework.org/schema/tx/spring-tx.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <!-- HandlerMapping -->
    <bean class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping"/>

    <!-- HandlerAdapter -->
    <bean class="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter"/>

    <!-- ViewResolver -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

    <bean name="/hello" class="controller.HelloWorldController"/>

    <mvc:interceptors>
        <bean class="Interceptor.MyFirstInterceptor"></bean>
        <bean class="Interceptor.MySecInterceptor"></bean>
    </mvc:interceptors>
</beans>

然后自己写的两个拦截器

package Interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyFirstInterceptor implements HandlerInterceptor {


    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("我是一号预处理，返回true");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("我是一号后处理");
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("一号请求处理完毕，视图已渲染，开始最终处理");
    }
}

package Interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MySecInterceptor implements HandlerInterceptor {


    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("我是二号预处理，我返回false");
        return false;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("我是二号后处理");
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("二号，请求处理完毕，视图已渲染，开始最终处理");
    }
}

一个处理器

package controller;

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HelloWorldController implements Controller {


    @Override
    public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
        System.out.println("我是处理器");
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("hello");
        modelAndView.addObject("message","hello world!!!!");
        return  modelAndView;
    }
}

然后执行。。。

正常流程咱们模拟一遍