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分享一些状态码400 404 500等原因:

出错: 前端:

// 获取所有的导航菜单    async getMenuList(){
         const {
   data:res} = await this.$http.get("menus");      console.log(res.data);      if( res.status != 200) return this.$message.error("操作失败！！！");      this.menuList = res.data;    },

后端：

@RestControllerpublic class MenuController {
       @Autowired    MenuDao menuDao;    @CrossOrigin    @RequestMapping("/menus")    public String getAllMenus(){
           System.out.println("sucess");        HashMap
   
     data = new HashMap<>();        List
    
      mainMenus = menuDao.getMainMenus();        data.put("data",mainMenus);        data.put("status",200);        String data_json = JSON.toJSONString(data);        System.out.println("成功访问！！！");        return data_json;    }}
    
   

xml文件:

   
       
            
             
             
             
                 
                  
                  
              
         
        
            SELECT mm.*,sm.id as sid ,               sm.title as stitle,sm.path as spath FROM mainmenu mm ,           submenu sm WHERE mm.id = sm.mid;     
   

检查后发现是配置文件写错，修改为:

spring:  datasource:    #MySQL配置    driverClassName:  com.mysql.cj.jdbc.Driver    url: jdbc:mysql://localhost:3308/data1?useSSL=false&useUnicode=true&characterEncoding=UTF-8&useSSL=false&serverTimezone=UTC    username: heziyi    password: 123456

修改完后再次启动，没有报错了

错误码404：

发现是因为controller类上面没有加@RestController注解

2.17日又一次出现错误码500

response报错：

{“timestamp”:“2021-02-17T08:22:46.911+0000”,“status”:500,“error”:“Internal

Server Error”,“message”:“Invalid bound statement (not found):

com.naughty.userlogin02.dao.TeacherDao.getTeacherCounts”,“path”:"/allteacher"}

自己的TeacherDao中有一句话:

public int getTeacherCounts(@Param(“name”) String name); 然后查了一下发现有可能是因为xml中没有对应的语句造成的，在xml中加上：

        SELECT count(*) FROM `teacherlist`                    WHERE name like #{name}            

再运行已经成功了，前端页面能够正常显示数据：

2.21

出现错误码500原因之一: xml文件中方法名的大小写与接口中的方法名大小写没对上 之后仍然再次出现错误码500 信息:

Cannot determine value type from string ‘数学’; nested exception is java.sql.SQLDataException: Cannot determine value type from string

Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: Error attempting to get column ‘title’ from result set. Cause: java.sql.SQLDataException: Cannot determine value type from string ‘数学’

; Cannot determine value type from string ‘数学’; nested exception is java.sql.SQLDataException: Cannot determine value type from string ‘数学’] with root cause

在message实体类中加上无参构造函数之后解决。

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