SpringBoot整合MyBatis

1. 在pom文件中添加以下坐标，增加mybatis依赖，和数据库驱动依赖

   <!--导入Mybatis依赖坐标-->
   <dependency>
       <groupId>org.mybatis.spring.boot</groupId>
       <artifactId>mybatis-spring-boot-starter</artifactId>
       <version>${mybatis.version}</version>
   </dependency>
   <!--导入mysql依赖，如果mysql版本是5.7，则应使用mysql:mysql-connector-java-->
   <dependency>
       <groupId>com.mysql</groupId>
       <artifactId>mysql-connector-j</artifactId>
   </dependency>
   

2. 删除resources目录下的application.properties，并新建application.yml对数据库连接进行配置

   # 配置数据库连接
   spring:
     datasource:
       url: jdbc:mysql:///springboot_demo
       username: root
       password: 123456
       driver-class-name: com.mysql.cj.jdbc.Driver
   

3. 配置Mybatis

   mybatis:
     # 配置实体类别名
     type-aliases-package: com.starry.demo.entity
     # 配置mapper.xml位置
     mapper-locations: classpath:mapper/*.xml
     # 下划线转驼峰
     configuration:
       map-underscore-to-camel-case: true
   

4. application.yml

   # 配置数据库连接
   spring:
     datasource:
       url: jdbc:mysql:///
       username: root
       password: 123456
       driver-class-name: com.mysql.cj.jdbc.Driver
   
   mybatis:
     # 配置实体类别名
     type-aliases-package: com.starry.demo.entity
     # 配置mapper.xml位置
     mapper-locations: classpath:mapper/*.xml
   

5. 在启动类上加上@MapperScan注解

   package com.starry.demo;
   
   import org.mybatis.spring.annotation.MapperScan;
   import org.springframework.boot.SpringApplication;
   import org.springframework.boot.autoconfigure.SpringBootApplication;
   
   @SpringBootApplication
   // 配置mybatis的扫描路径
   @MapperScan("com.starry.demo.dao")
   public class DemoApplication {
   
       public static void main(String[] args) {
           SpringApplication.run(DemoApplication.class, args);
       }
   
   }
   

6. 执行以下sql脚本

   CREATE TABLE `sys_user`(
   	user_id bigint not null primary key auto_increment,
   	username VARCHAR(50) not null unique,
   	`password` varchar(64) not null,
   	`email` varchar(50) null,
   	`phone` varchar(50) null,
   	create_time datetime,
   	update_time datetime,
   	create_by varchar(50),
   	update_by varchar(50)
   );
   

7. 新建entity包并新增实体类

   package com.starry.demo.entity;
   
   import lombok.Data;
   
   import java.util.Date;
   
   @Data
   public class SysUser {
       
       private Long userId;
       
       private String username;
       
       private String password;
       
       private String email;
       
       private String phone;
       
       private Date createTime;
       
       private Date updateTime;
       
       private String createBy;
       
       private String updateBy;
       
   }
   
   

8. 新建dao包并编写SysUserDao接口

   package com.starry.demo.dao;
   
   import com.starry.demo.entity.SysUser;
   import org.springframework.stereotype.Repository;
   
   @Repository // 这个注解表示它是一个数据访问层
   public interface SysUserDao {
       
       SysUser selectByUsername(String username);
       
       int insert(SysUser sysUser);
       
   }
   

9. 在resouces目录下新建mapper目录并在此编写SysUserMapper.xml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.starry.demo.dao.SysUserDao">
   
       <select id="selectByUsername" resultType="sysUser" parameterType="string">
           select *
           from sys_user
           where username = #{username}
       </select>
   
       <insert id="insert" parameterType="sysUser">
           insert into sys_user(`username`, `password`, `email`, `phone`, `create_time`, `create_by`)
           values (#{username}, #{password}, #{email}, #{phone}, now(), #{createBy})
       </insert>
   
   </mapper>
   

10. 新建service和service.impl包并编写SysUserService和SysUserServiceImpl的代码

package com.starry.demo.service;

import com.starry.demo.entity.SysUser;

public interface SysUserService {

    SysUser getByUsername(String username);

    boolean saveOrUpdate(SysUser sysUser);

}

package com.starry.demo.service.impl;

import com.starry.demo.dao.SysUserDao;
import com.starry.demo.entity.SysUser;
import com.starry.demo.service.SysUserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class SysUserServiceImpl implements SysUserService {

    private final SysUserDao sysUserDao;

    public SysUserServiceImpl(SysUserDao sysUserDao) {
        this.sysUserDao = sysUserDao;
    }

    @Override
    public SysUser getByUsername(String username) {
        return sysUserDao.selectByUsername(username);
    }

    @Override
    public boolean saveOrUpdate(SysUser sysUser) {
        // 判断sysUser的主键是否为null或为0
        if (sysUser.getUserId() == null || sysUser.getUserId() == 0) {
            // 执行新增操作
            return sysUserDao.insert(sysUser) > 0;
        }
        // 执行修改操作
        return false;
    }
}

11. 新建controller并创建SysUserController

    package com.starry.demo.controller;
    
    import com.starry.demo.entity.SysUser;
    import com.starry.demo.service.SysUserService;
    import org.springframework.web.bind.annotation.*;
    
    @RestController
    @RequestMapping("/sys/user")
    public class SysUserController {
        
        private final SysUserService sysUserService;
    
        public SysUserController(SysUserService sysUserService) {
            this.sysUserService = sysUserService;
        }
        
        @GetMapping
        public SysUser getByUsername(String username) {
            return sysUserService.getByUsername(username);
        }
        
        @PostMapping
        public boolean add(@RequestBody SysUser sysUser) {
            return sysUserService.saveOrUpdate(sysUser);
        }
        
    }