SpringMVC -- 拦截器

一.拦截器

定义拦截器，实现HandlerInterceptor接口

package com.huan.web;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class Interceptor implements HandlerInterceptor{

    //进入Handler方法之前执行
    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        //return false表示拦截，不向下执行
        //return true表示放行
        return false;
    }

    //进入Handler方法之后，返回modelAndView之前执行
    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {

    }

    //执行Handle之后执行
    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
    }
}

可以从名称和参数看出各个接口的顺序和作用:

public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception

参数最少，只有三个
进入 Handler方法之前执行
用于身份认证、身份授权。比如身份认证，如果认证通过表示当前用户没有登陆，需要此方法拦截不再向下执行

public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, 
ModelAndView modelAndView) throws Exception

多了一个modelAndView参数
进入Handler方法之后，返回modelAndView之前执行
应用场景从modelAndView出发：将公用的模型数据(比如菜单导航)在这里传到视图，也可以在这里统一指定视图

public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, 
Exception ex) throws Exception

多了一个Exception的类型的参数
执行Handler完成执行此方法
应用场景：统一异常处理，统一日志处理

二.拦截器配置

针对HandlerMapping配置

springmvc拦截器针对HandlerMapping进行拦截设置，如果在某个HandlerMapping中配置拦截，经过该HandlerMapping映射成功的handler最终使用该拦截器。

<bean class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping">
        <property name="interceptors">
            <list>
                <ref bean="handlerInterceptor1"/>
                <ref bean="handlerInterceptor2"/>
            </list>
        </property>
    </bean>
    <bean id="handlerInterceptor1" class="com.huan.web.Interceptor1.Interceptor1"/>
    <bean id="handlerInterceptor2" class="com.huan.web.Interceptor1.Interceptor2"/>

不推荐使用

类似全局的拦截器

springmvc配置类似全局的拦截器，springmvc框架将配置的类似全局的拦截器注入到每个HandlerMapping中。

    <!--拦截器 -->
    <mvc:interceptors>
        <!--多个拦截器,顺序执行 -->
        <mvc:interceptor>
            <!-- /**表示所有url包括子url路径 -->
            <mvc:mapping path="/**"/>
            <bean class="com.huan.web.Interceptor1.Interceptor1"></bean>
        </mvc:interceptor>
        <mvc:interceptor>
            <mvc:mapping path="/**"/>
            <bean class="com.huan.web.Interceptor1.Interceptor2"></bean>
        </mvc:interceptor>
    </mvc:interceptors>

三.多拦截器测试

拦截器一:Interceptor1.java

package com.huan.web.Interceptor1;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Interceptor1 implements HandlerInterceptor{

    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("拦截器一执行------preHandle");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("拦截器一执行-------postHandle");
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("拦截器一执行------afterCompletion");
    }
}

拦截器二：Interceptor2.java

package com.huan.web.Interceptor1;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Interceptor2 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("拦截器二执行------preHandle");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("拦截器二执行-------postHandle");

    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("拦截器二执行------afterCompletion");

    }
}

- 两个拦截器的preHandle都返回true

结论：preHandle按照顺序执行，postHandle、afterCompletion按照逆向顺序执行

- 拦截器一放行，拦截器二不放行

总结：
拦截器1放行，拦截器2 preHandle才会执行。
拦截器2 preHandle不放行，拦截器2 postHandle和afterCompletion不会执行。
只要有一个拦截器不放行，postHandle不会执行。

- 拦截器一不放行，拦截器二放行

总结：
拦截器1 preHandle不放行，postHandle和afterCompletion不会执行。
拦截器1 preHandle不放行，拦截器2不执行。

- 拦截器一不放行，拦截器二不放行