springboot 2.3 使用@WebFilter注解 添加登陆过滤器

注意：此处用于前后端分离的项目，所以返回是json字符串

	  自定义 Filter 有两种实现⽅式：
	  第一种是使⽤用 @WebFilter
	  第二种是使⽤FilterRegistrationBean			 

1.yml中配置

server:
  port: 8081
  servlet:
    context-path: /hnezzsbm  #springboot默认没有项目名
accessPath: /login,/register,/sendPost,/retrievePass,/entroll/getZsbmStudentAchievement #不用登陆就可以访问的接口

2.启动类上要加上@ServletComponentScan注解
加上此注解，Servlet（控制器）、Filter（过滤器）、Listener（监听器）可以直接通过@WebServlet、@WebFilter、@WebListener注解自动注册到Spring容器中，无需其他代码。

3.创建过滤器代码

package com.iflytek.edu.hnezzhxy.filter;

import com.alibaba.fastjson.JSONObject;
import com.iflytek.edu.hnezzhxy.common.config.Constants;
import com.iflytek.edu.hnezzhxy.common.enums.ResponseCodeEnum;
import com.iflytek.edu.hnezzhxy.util.ResponseResultUtil;
import com.iflytek.edu.hnezzhxy.vo.ResultVO;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.http.MediaType;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
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.nio.charset.Charset;

/**
 * @create: 2018-03-12 13:20:54
 * @version 1.0
 */
@WebFilter(filterName = "sessionFilter",urlPatterns = {"/*"})
public class SessionFilter implements Filter {

    private static final Logger logger = LoggerFactory.getLogger(SessionFilter.class);

    /** 不需要登录就可以访问的路径(比如:注册登录等) **/
    @Value("${accessPath}")
    private String[] includeUrls;
    /** 项目路径 **/
    @Value("${server.servlet.context-path}")
    private String contextPath;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {}

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        HttpSession session = request.getSession(false);
        String uri = request.getRequestURI();
        //是否需要过滤
        Boolean needFilter = isNeedFilter(uri);
        if (!needFilter) {
            //不需要过滤直接传给下一个过滤器
            filterChain.doFilter(servletRequest, servletResponse);
        } else { //需要过滤器
            // session中包含user对象,则是登录状态
            if(session!=null&&session.getAttribute(Constants.SESSION_USER_Attribute) != null){
                filterChain.doFilter(request, response);
            }else{
                String requestType = request.getHeader("X-Requested-With");
                response.setContentType(MediaType.APPLICATION_JSON_VALUE);
                response.setCharacterEncoding(Charset.forName(Constants.ECODE_UTF8).displayName());
                PrintWriter writer = response.getWriter();
                //判断是否是ajax请求
                if(requestType!=null && "XMLHttpRequest".equals(requestType)){
                    ResultVO result = new ResponseResultUtil().success(ResponseCodeEnum.LOGIN_SUCCESS.getCode(),
                            ResponseCodeEnum.LOGIN_SUCCESS.getMessage(), null, true);
                    writer.write(JSONObject.toJSON(result).toString());
                }else{
                    //重定向到登录页(需要在static文件夹下建立此html文件)
                    logger.info("尚未登陆，跳转登陆页面!");
                    ResultVO result = new ResponseResultUtil().success(ResponseCodeEnum.UNLOGIN_ERROR.getCode(),
                            ResponseCodeEnum.UNLOGIN_ERROR.getMessage(), null, true);

                    writer.write(JSONObject.toJSON(result).toString());
                }
                return;
            }
        }

    }

    /**
     * @Description: 是否需要过滤
     * @Date: 2018-03-12 13:20:54
     * @param uri
     */
    public Boolean isNeedFilter(String uri) {

        for (String includeUrl : includeUrls) {
            String newIncludeUrl=contextPath+includeUrl;
            if(newIncludeUrl.equals(uri)) {
                return false;
            }
        }

        return true;
    }

    @Override
    public void destroy() {}
}

4.这种添加过滤器不能控制过滤器的执行顺序，所以一般推荐用FilterRegistrationBean过滤器方式