【Java Web】用拦截器的方式获取用户信息

流程：从cookie中获取凭证，根据凭证查询用户，并在本次请求中持有用户，在视图模板上显示登录用户的信息。

1. 定义拦截器

java 复制代码

package com.nowcoder.community.controller.Interceptor;

import com.nowcoder.community.entity.LoginTicket;
import com.nowcoder.community.entity.User;
import com.nowcoder.community.service.UserService;
import com.nowcoder.community.util.CookieUtil;
import com.nowcoder.community.util.HostHolder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Date;

@Component

public class LoginTicketInterceptor implements HandlerInterceptor {

    @Autowired
    private UserService userService;

    @Autowired
    private HostHolder hostHolder;

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 从cookie中获取凭证
        String ticket = CookieUtil.getValue(request, "ticket");
        if(ticket != null){  // 已经登陆
            LoginTicket loginTicket = userService.findLoginTicket(ticket);
            // 检查ticket是否有效
            if(loginTicket != null && loginTicket.getExpired().after(new Date()) &&loginTicket.getStatus()==0){
                // 根据凭证查询用户
                User user = userService.findUserById(loginTicket.getUserId());
                // 在本次请求中持有用户
                hostHolder.setUsers(user);
            }
        }
        return true;
    }

    // 在模板引擎之前使用user，将user放到model里
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        User user = hostHolder.getUser();
        if(user != null && modelAndView != null){
            modelAndView.addObject("loginUser",user);
        }
    }

    // 在模板引擎启动后清掉threadlocal，防止内存泄露
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        hostHolder.clear();
    }
}

2. 配置拦截器

java 复制代码

package com.nowcoder.community.config;

import com.nowcoder.community.controller.Interceptor.AlphaInterceptor;
import com.nowcoder.community.controller.Interceptor.LoginTicketInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration

public class WebMvcConfig implements WebMvcConfigurer {

    @Autowired
    private AlphaInterceptor alphaInterceptor;

    @Autowired
    private LoginTicketInterceptor loginTicketInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // 通过重写addInterceptors()方法，可以配置拦截器，对请求进行预处理或后处理。
        registry.addInterceptor(alphaInterceptor)
                .excludePathPatterns("/**/*.css", "/**/*.js", "/**/*.png", "/**/*.jpg", "/**/*.jpeg")
                .addPathPatterns("/register","/login");

        registry.addInterceptor(loginTicketInterceptor)
                .excludePathPatterns("/**/*.css", "/**/*.js", "/**/*.png", "/**/*.jpg", "/**/*.jpeg");

    }
}