This is my code,it can get the response with 200 but the database doesn't update.The backend told that it had received null.

          axios.post('api/nosql/LineController/insertLine',  {
            line:{
              id:this.id,
              directional:this.directional,
              kilometer:this.slide1.distance,
              runtime:runtime,
              interval:this.slide2.shift,
              type:this.type,
            },
            stationList: this.newPlatforms,
            
          })

And I also tried this code, the problem remained.

        axios({
          method:"post",
          changeOrigin:"true",
          url:"api/nosql/LineController/insertLine",
          transformRequest:[
            function(data){
              return QS.stringify(data);
            }
          ],
          data: {
            line:{
              id:this.id,
              directional:this.directional,
              kilometer:this.slide1.distance,
              runtime:runtime,
              interval:this.slide2.shift,
              type:this.type,
            },
            stationList: this.newPlatforms,
          }
        })

the code at backend

public Object insertLine(HttpServletRequest request) throws IOException {
        StringBuffer lineInfoAndStations = new StringBuffer();
        String line;
        BufferedReader reader;

        reader = request.getReader();
        while(null != (line = reader.readLine())) {
            lineInfoAndStations.append(line);
        }

        return service.addLine(lineInfoAndStations.toString());
    }