[Java知识库]Spring笔记(5):拦截器的使用（以登录请求与拦截为例）

实现拦截器自定义

package com.CakeCN.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 MyInterceptor1 implements HandlerInterceptor {
    //在目标方法执行之前 执行
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...");
        return false;
    }

    //目标方法执行后，视图返回前执行
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...");
    }

    //视图都已经返回后，执行
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }
}

Spring-mvc.xml中配置拦截器

所有访问控制器的请求都会先经过这个拦截器

<!--    配置拦截器-->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**"/> 
            <bean class="com.CakeCN.interceptor.MyInterceptor1"/>
        </mvc:interceptor>
    </mvc:interceptors>

在拦截器中设置先检查session中有无登录信息，如果有就正确处理请求，如果无就重定向到登陆界面

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...");
        //判断用户是否登录， 通过判断session中有没有user
        HttpSession session = request.getSession();
        User user = (User) session.getAttribute("user");
        if(user == null){
            response.sendRedirect("/login.jsp");
            return false;
        }
        return true;
    }

注意要在配置拦截器时，将登录的请求放行

<!--    配置拦截器-->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**"/>
            <mvc:exclude-mapping path="/login"/>
            <bean class="com.CakeCN.interceptor.MyInterceptor1"/>
        </mvc:interceptor>
    </mvc:interceptors>

    @RequestMapping("login")
    public ModelAndView login(String username, String password, HttpSession session){
        ModelAndView modelAndView = new ModelAndView();
        //对比数据库用户登录信息是否正确
        // ......

        User user = new User();
        user.setUsername(username);
        modelAndView.setViewName("success.jsp");
        modelAndView.addObject("username",username);
        session.setAttribute("user", user);
        return modelAndView;
    }