牛客网项目---1.6.显示登录信息
5、使用拦截器显示登录信息：通过cookie获得ticket，通过ticket获取loginticket对象，进而获得loginticket。
userID得到userId，进而获得user，将user存到hostHolder中，让本次请求中持有用户，为防止并发请求，需要对每个请求线程数据做隔离，使用ThreadLocal来set和get用户user，用完要清理release，同时还能代替session，减少服务器压力；
6、配置拦截器：先注入拦截器bean，再添加需要拦截的界面即可
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1.编写获取Cookie的工具类CookieUtil：
package com.nowcoder.community.util;import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;public class CookieUtil {public static String getValue(HttpServletRequest request,String name){if (request==null||name==null){throw new IllegalArgumentException("参数为空!");}Cookie[] cookies = request.getCookies();if (cookies!=null){for (Cookie cookie : cookies) {if (cookie.getName().equals(name)){return cookie.getValue();}}}return null;}
}2.编写线程容器工具类HostHolder：
package com.nowcoder.community.util;import com.nowcoder.community.entity.User;
import org.springframework.stereotype.Component;/*** 持有用户信息，用于代替session对象*/
@Component
public class HostHolder {private ThreadLocal users=new ThreadLocal<>();public void setUser(User user){users.set(user);}public User getUser(){return users.get();}public void clear(){users.remove();}
}3.编写拦截器LoginTicketInterceptor：
package com.nowcoder.community.interceptor;import com.nowcoder.community.entity.LoginTicket;
import com.nowcoder.community.entity.User;
import com.nowcoder.community.service.LoginTicketServiceImpl;
import com.nowcoder.community.service.UserServiceImpl;
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 {@Autowiredprivate HostHolder hostHolder;@Autowiredprivate LoginTicketServiceImpl loginTicketService;@Autowiredprivate UserServiceImpl userService;@Overridepublic 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){//查询凭证LoginTicket loginTicket = loginTicketService.selectByTicket(ticket);//查询凭证是否有效if (loginTicket!=null&&loginTicket.getStatus()==0&&loginTicket.getExpired().after(new Date())){//根据凭证查询用户User user = userService.selectById(loginTicket.getUserId());//在本次请求中持有用户hostHolder.setUser(user);}}return true;}@Overridepublic 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);}}@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {hostHolder.clear();}
}4.配置拦截器WebMvcConfig：
package com.nowcoder.community.config;import com.nowcoder.community.interceptor.LoginRequiredInterceptor;
import com.nowcoder.community.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 {@Autowiredprivate LoginTicketInterceptor loginTicketInterceptor;@Autowiredprivate LoginRequiredInterceptor loginRequiredInterceptor;@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(loginTicketInterceptor).excludePathPatterns("/**/*.css","/**/*.js","/**/*.jpg","/**/*.png","/**/*.jpeg");registry.addInterceptor(loginRequiredInterceptor).excludePathPatterns("/**/*.css","/**/*.js","/**/*.jpg","/**/*.png","/**/*.jpeg");}
}5.index.html：
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