1.登陆拦截器

package com.dzqc.yx.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import com.alibaba.fastjson.JSONObject;
import com.dzqc.yx.util.AjaxResult;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
    /**
     * 登录拦截器
     * @author Boost
     */
public class LoginInterceptor implements HandlerInterceptor {
        /**
         * 开始进入地址请求拦截
         */
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
                throws Exception {
            HttpSession session = request.getSession();
            if(session.getAttribute("user") != null){
                return true;
            }else{
            	String jsonObjectStr = JSONObject.toJSONString(new AjaxResult(1186,false,"login_error",null));
                returnJson(response,jsonObjectStr);
                return false;
            }
        }
        
        /**
         * 认证失败返回json数据
         * @param response
         * @param json
         * @throws Exception
         */
        @SuppressWarnings("unused")
		private void returnJson(HttpServletResponse response, String json) throws Exception{
            PrintWriter writer = null;
            response.setCharacterEncoding("UTF-8");
            response.setContentType("text/html; charset=utf-8");
            try {
                writer = response.getWriter();
                writer.print(json);
     
            } catch (IOException e) {
            } finally {
                if (writer != null)
                    writer.close();
            }
        }
        
        /**
         * 处理请求完成后视图渲染之前的处理操作
         */
        @Override
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
                               ModelAndView modelAndView) throws Exception {
        }

        /**
         * 视图渲染之后的操作
         */
        @Override
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
                throws Exception {
        }
        /**
         * 定义排除拦截URL
         * @return
         */
        public static List<String> getUrl(){
        	List<String> url = new ArrayList<String>();
            url.add("/tologin");    //登录页
            url.add("/login/in");   //登录action URL
            return url;
        }
    }

在preHandle方法的else语句块中也可以进行从定向到登陆页面，例

response.sendRedirect("/admin/login");	//未登录，跳转到登录页

2.启用拦截器

package com.dzqc.yx.interceptor;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/***
 * 注册拦截器
 */
@Configuration
public class WebappAdapter implements WebMvcConfigurer {
    /**
     * 注册拦截器
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor()).addPathPatterns("/**").excludePathPatterns(LoginInterceptor.getUrl());
        WebMvcConfigurer.super.addInterceptors(registry);
    }
}

未登录时返回