目录

一、拦截器示例

1. 定义拦截器，实现HandlerInterceptor接口

import org.slf4j.Logger;import org.slf4j.LoggerFactory;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;@Componentpublic class Alphainterceptor implements HandlerInterceptor {    private static final Logger logger = LoggerFactory.getLogger(Alphainterceptor.class);    // 在Controller之前执行    @Override    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {        logger.debug("preHandler:" + handler.toString());        return true;    }    // 在Controller之后、TemplateEngine之前执行    @Override    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {        logger.debug("postHandle:" + handler);    }    // 在TemplateEngine之后执行    @Override    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {        logger.debug("afterCompletion:" + handler);    }}

2. 配置拦截器，为它指定拦截、排除的路径

excludePathPatterns：排除不需要被拦截的路径addPathPatterns：添加需要拦截的路径

import com.nowcoder.community.community.controller.interceptor.Alphainterceptor;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;@Configurationpublic class WebMvcConfig implements WebMvcConfigurer {    // 从容器中获取自定义的拦截器，并实例化    @Autowired    private Alphainterceptor alphainterceptor;    @Override    public void addInterceptors(InterceptorRegistry registry) {        registry.addInterceptor(alphainterceptor)                .excludePathPatterns("/**/*.css" ,"/**/*.js" ,"/**/*.png" ,"/**/*.jpg" ,"/**/*.jpeg" )                .addPathPatterns("/register","/login");    }}

二、拦截器应用

通过ticket凭证获取User对象后，需要把User对象存下来，以便后续使用。问题是该怎样存呢？ 如果只是简单地存到一个工具类或容器当中，在C/S多对一的多线程环境下，会出现并发等线程安全问题；我们可以通过ThreadLocal使线程和数据一一对应地来存取，以Map集合（线程作为key，数据作为value）的方式隔离不同线程的不同信息，使每个线程单独存一份，互相之间不干扰。 通常我们把隔离线程这个逻辑封装成一个工具类(通常命名为HostHolder)，并注入到容器中。

import com.nowcoder.community.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 {

    // 以Map集合(线程作为key，User对象作为value)的方式隔离不同线程的不同信息
    private ThreadLocal<User> users = new ThreadLocal<>();

    public void setUser(User user){
        users.set(user);
    }

    public User getUser(){
        return users.get();
    }

    public void clear(){
        users.remove();
    }

}

1. 在请求开始时查询用户登录

import com.nowcoder.community.community.entity.LoginTicket;
import com.nowcoder.community.community.entity.User;
import com.nowcoder.community.community.service.UserService;
import com.nowcoder.community.community.util.CookieUtils;
import com.nowcoder.community.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;

    // 请求开始时查询用户登录
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 从cookie中获取凭证
        String ticket = CookieUtils.getValue(request, "ticket");
        if(ticket != null){
            // 查询凭证
            LoginTicket loginTicket = userService.findLoginTicket(ticket);
            // 检查凭证是否有效
            if(loginTicket != null && loginTicket.getStatus() == 0 && loginTicket.getExpired().after(new Date())){
                // 凭证有效
                User user = userService.findUserById(loginTicket.getUserId());
                // 在本次请求中持有用户
                hostHolder.setUser(user);
            }
        }

        return true;
    }

}

2. 在本次请求中持有用户数据

以下代码存在于1.的类中

// 在本次请求中持有用户数据
    @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);
        }
    }

3. 在模板视图上显示用户数据

4. 在请求结束时清理用户数据

// 在请求结束时清理用户信息
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        hostHolder.clear();
    }