springboot获取mysql数据库数据报错

Question

springboot获取数据库数据报错

User.java代码

package com.example.demo.entity;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;

import javax.annotation.Resource;

@Resource
@TableName("user")
public class User {
@TableId(type = IdType.AUTO)
public Integer userId;
public String userName;
public Integer userSex;

public Integer getUserId() { return userId; }

public void setUserId(Integer user_Id) {
    this.userId = user_Id;
}

public String getUserName() {
    return userName;
}

public void setUserName(String user_Name) {
    this.userName = user_Name;
}

public Integer getUserSex() {
    return userSex;
}

public void setUserSex(Integer user_Sex) {
    this.userSex = user_Sex;
}

@Override
public String toString() {
    return "User{" +
            "userId=" + userId +
            ", userName='" + userName + '\'' +
            ", userSex=" + userSex +
            '}';
}

}

UserController.java部分代码
@GetMapping("user/get")
public String mysqlGet() {
User user = userDao.selectById(1);
return user.toString();
}

java.lang.NullPointerException: null

目前没找到结局方案

想要成功获取数据库数据

Answer 1

没有id为1的用户吧。。。