错误信息：Could not write JSON: (was java.lang.NullPointerException); nested exception is com.faster

This error occurs because there is an object at the time of transfer json property is null, So now, the last in the top of the class with a comment

//主要就是个注解，最后错误消失，程序正常运行
@JsonInclude(JsonInclude.Include.NON_NULL)
public class ArcType implements Serializable {
}```