以前都是用Springboot+jdbcTemplate實現CRUD
但是趨勢是用mybatis，今天稍微修改，創建springboot + mybatis 的項目，實現簡單的CRUD
上圖是項目的目錄結構，創建一個user實體，包含id，姓名，手機，密碼，flag等信息，然后對用戶進行增刪查改。
drop table if exists user; CREATE TABLE `user` ( id tinyint(4) NOT NULL AUTO_INCREMENT, name varchar(200) NOT NULL, age int(11) NOT NULL,、 phone varchar(20) NOT NULL, password varchar(20) NOT NULL, flag int(4), PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
用Intellij IDEA進行開發，創建一個新的springboot項目，選中SQL中的mybaits，生成之后默認帶有DemoApplication主函數啟動類，最后啟動的時候要在主函數上添加mapper掃描@MapperScan("com.example.demo.mapper") //掃描全部mapper
其他的代碼依次如下： User
public class User implements Serializable {
private Long id;
private String name;
private int age;
private String phone;
private String password;
private boolean flag;
省略了getter and setter
}
userService
package com.example.demo.service;
import com.example.demo.pojo.User;
import java.util.List;
public interface userService {
List<User> findAll();
List<User> selectAll();
List<User> selectById(int id);
int create(User user);
int updateUserById(User user);
int deleteUserById(int id);
}
userServiceImp
package com.example.demo.serviceImp;
import com.example.demo.mapper.userMapper;
import com.example.demo.pojo.User;
import com.example.demo.service.userService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
@Service
public class userServiceImp implements userService {
@Autowired
private userMapper userMapper;
public List<User> findAll() {
System.err.println("查詢所有用戶接口");
List<User> list = userMapper.findAll();
return list;
}
@Override
public List<User> selectAll() {
List<User> list = userMapper.selectAll();
return list;
}
@Override
public List<User> selectById(int id) {
List<User> list = userMapper.selectById(id);
return list;
}
@Override
public int create(User user) {
int count = userMapper.create(user);
return count;
}
@Override
public int updateUserById(User user) {
int count = userMapper.updateUserById(user);
return count;
}
@Override
public int deleteUserById(int id) {
int count = userMapper.deleteUserById(id);
return count;
}
}
userMapper
package com.example.demo.mapper;
import com.example.demo.pojo.User;
import java.util.List;
public interface userMapper {
List<User> findAll();
List<User> selectAll();
List<User> selectById(int id);
int create(User user);
int updateUserById(User user);
int deleteUserById(int id);
}
userController
package com.example.demo.controller;
import com.example.demo.pojo.User;
import com.example.demo.serviceImp.userServiceImp;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import java.util.List;
@Api(tags = {"demo接口"})
@Controller
@RequestMapping("user")
public class userController {
@Autowired
private userServiceImp userService;
@ApiOperation(value = "顯示全部用戶的信息倒序")
@RequestMapping("userLists")
@ResponseBody
public List<User> showUsers() {
List<User> list = userService.findAll();
return list;
}
@ApiOperation(value = "顯示全部用戶的信息")
@RequestMapping("selectAll")
@ResponseBody
public List<User> selectAll() {
List<User> list = userService.selectAll();
return list;
}
@ApiOperation(value = "根據ID查詢用戶的信息")
@RequestMapping("selectById")
@ResponseBody
public List<User> selectById(int id) {
List<User> list = userService.selectById(300);
return list;
}
@ApiOperation(value = "創建新用戶信息")
@PostMapping("create")
@ResponseBody
public String create(User user) {
int count = userService.create(user);
System.out.println(count);
if (count>0)
return ("成功添加"+count+"條記錄");
else
return "添加用戶失敗";
}
@ApiOperation(value = "根據ID更新用戶信息")
@PostMapping("updateUserById")
@ResponseBody
public String updateUserById(User user) {
int count = userService.updateUserById(user);
System.out.println(count);
if (count>0)
return ("成功更新"+count+"條記錄");
else
return "更新用戶失敗";
}
@ApiOperation(value = "根據ID刪除用戶信息")
@PostMapping("deleteUserById")
@ResponseBody
public String deleteUserById(int id) {
int count = userService.deleteUserById(id);
System.out.println(count);
if (count>0)
return ("成功刪除"+count+"條記錄");
else
return "刪除用戶失敗";
}
}
userMapper.xml 映射文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.demo.mapper.userMapper">
<resultMap id="userResultMap" type="com.example.demo.pojo.User">
<id column="id" property="id" jdbcType="BIGINT"/>
<result column="name" property="name" jdbcType="VARCHAR"/>
<result column="age" property="age" jdbcType="VARCHAR"/>
<result column="phone" property="phone" jdbcType="VARCHAR"/>
<result column="password" property="password" jdbcType="VARCHAR"/>
<result column="flag" property="flag" jdbcType="BIGINT"/>
</resultMap>
<select id="findAll" resultMap="userResultMap">
SELECT id,name,age,phone,password,flag FROM user order by id desc
</select>
<select id="selectById" parameterType ="int" resultMap="userResultMap">
select * from user where id = #{id}
</select>
<select id="selectAll" resultMap="userResultMap">
select * from user order by id desc
</select>
<insert id="create" parameterType="com.example.demo.pojo.User">
insert into user(name,age,phone,password,flag) values (#{name},#{age},#{phone},#{password},#{flag})
</insert>
<update id="updateUserById" parameterType="com.example.demo.pojo.User">
update user set name = #{name},age =#{age},phone =#{phone},password = #{password},flag = #{flag} where id = #{id}
</update>
<delete id="deleteUserById" parameterType ="int">
delete from user where id = #{id}
</delete>
</mapper>
1. Mapper method 'com.example.demo.mapper.userMapper.create attempted to return null from a method with a primitive return type (int).] with root cause
是新增用戶信息接口，發現用戶信息已經成功插入數據庫，但是頁面提示
There was an unexpected error (type=Internal Server Error, status=500).
Mapper method 'com.example.demo.mapper.userMapper.create attempted to return null from a method with a primitive return type (int).
出錯原因很簡單,mapper.xml 映射文件中，新增記錄應該用insert，我懶，直接復制了上面的select， 然后搓了很久。。
2. 找不到Bean
出錯原因很簡單,啟動類主函數沒有添加mapper掃描，需要添加@MapperScan("com.example.demo.mapper")
這個項目的github地址是https://github.com/JasmineQian/SpringDemo_2019/tree/master/springboot2mybatis
以前我管理github很亂，自己看到的代碼，自己擼的代碼，都隨便網上塞，然后之后都不怎么回顧。然后就學過什么都忘記了。隱約記得遇到過，具體解決方法不知道。
就像《少林英雄》歌中常的那樣，
練功必須頂大太陽 （哼）
晚上還要借月亮光（哈）
一日不練十日空（哼哈）
一日不擼十日空~~~擼代碼，要像練功一樣每日堅持！