springMVC拦截器返回错误信息给前端

墨蓝 2023-02-17 11:05 48阅读 0赞

springMVC拦截器的preHandle方法返回值是Boolean类型，所以条件够就放行，执行方法，而条件不足，前端无法知道是什么原因而被拦截，下面来解决这个问题。

一. 编写一个拦截器（该拦截器作用是：判断用户是否登录并且权限是否足够）

package com.mmall.controller.common.intercept;
    
    import com.mmall.common.Constants;
    import com.mmall.common.ResponseCode;
    import com.mmall.common.ServerResponse;
    import com.mmall.pojo.User;
    import com.mmall.util.JsonUtil;
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.web.servlet.HandlerInterceptor;
    import org.springframework.web.servlet.ModelAndView;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.PrintWriter;
    
    /** * @author Luyue * @date 2018/8/17 18:02 **/
    @Slf4j
    public class AuthorityTestIntercepter implements HandlerInterceptor { 
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { 
            HttpSession session = request.getSession();
            User user = (User) session.getAttribute(Constants.CURRENT_USER);
            if (user == null || user.getRole().intValue() != Constants.ROLE.ROLE_ADMIN) { 
                return false;
            }
    
            log.info("preHandle");
            return true;
        }
    
        @Override
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { 
    
        }
    
        @Override
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { 
    
        }
    }

二. 注册该拦截器  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2R4eXpoYmI_size_16_color_FFFFFF_t_70]  
具体拦截路径可以自行更改

三. 更改拦截器，返回信息给前端

不改变之前： 什么信息都没有  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2R4eXpoYmI_size_16_color_FFFFFF_t_70 1]  
更改拦截器:

public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception \{  
HttpSession session = request.getSession();  
User user = (User) session.getAttribute(Constants.CURRENT\_USER);  
if (user == null || user.getRole().intValue() != Constants.ROLE.ROLE\_ADMIN) \{  
//重置response  
response.reset();  
//设置编码格式  
response.setCharacterEncoding(“UTF-8”);  
response.setContentType(“application/json;charset=UTF-8”);

PrintWriter pw = response.getWriter();
    
        if (user == null) {
            pw.write(JsonUtil.objToJson(ServerResponse.createByErrorCodeAndMessage(ResponseCode.NEED_LOGIN.getCode(), "拦截器拦截，请登录")));
        } else {
            pw.write(JsonUtil.objToJson(ServerResponse.createByErrorCodeAndMessage(ResponseCode.ERROR.getCode(), "拦截器拦截，无权限操作")));
        }
    
        pw.flush();
        pw.close();
        return false;
    }
    
    log.info("preHandle");
    return true;

\}  
效果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2R4eXpoYmI_size_16_color_FFFFFF_t_70 2]  
这篇文章没有写全面，其中pw.write(JsonUtil.objToJson(ServerResponse.createByErrorCodeAndMessage(ResponseCode.NEED\_LOGIN.getCode(), “拦截器拦截，请登录”)));  
这句代码中JsonUtil.objToJson这个方法没有给出代码。  
不过文章的思路可以参考。  
可以把缺失的部分代码换成下面的代码。

response.setCharacterEncoding("UTF-8");  
    response.setContentType("application/json; charset=utf-8");
    PrintWriter out = null ;
    try{ 
        JSONObject res = new JSONObject();
        res.put("success","false");
        res.put("msg","xxxx");
        out = response.getWriter();
        out.append(res.toString());
        return false;
    }
    catch (Excepton e){ 
        e.printStackTrace();
        response.sendError(500);
        return false;
    }

以解决上面的问题。

参考文章：  
https://blog.csdn.net/qq\_37585236/article/details/81781563  
https://blog.csdn.net/u012201619/article/details/75156707/

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