阅读目录

一、什么是MyBatis

二、整合MyBatis

三、用注解方式使用 MyBatis

四、用配置方式使用 MyBatis

MyBatis 在Spring Boot应用非常广，非常强大的一个半自动的ORM框架。

代码下载：

https://github.com/Jackson0714/study-spring-boot.git

《深入浅出Spring Boot系列》

05. 深入浅出Spring Boot - 数据访问之JDBC（源码分析+代码下载）

06. 深入浅出 Spring Boot - 数据访问之Druid（附代码下载）

本文一共2778字，阅读需要10分钟

一、什么是MyBatis

支持定制化SQL、存储过程以及高级映射的优秀的持久层框架
避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集
可以对配置和原生Map使用简单的 XML 或注解
将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录
数据库、数据源、数据库连接池、JDBC、JDBC实现是什么关系？

JDBC：Java和关系型数据库的桥梁，是一个规范，不是实现。不同类型的数据库需要有自己的JDBC实现
数据源：包含数据库连接池，连接池管理。常见的有C3P0、HikariDataSoiurce、Druid等
连接池：预先创建一些数据库连接，放到连接池里面，用的时候从连接池里面取，用完后放回连接池
连接池管理：创建数据库连接，管理数据库连接
JDBC实现：MySQL JDBC实现、Oracle JDBC实现等其他实现
MyBatis对JDBC进行了封装

二、整合MyBatis

我们基于之前创建的项目spring-boot-06-data-druid 来创建spring-boot-07-data-mybatis项目

1）引入MyBatis依赖

<!-- mybatis -->
<dependency>
  <groupId>org.mybatis.spring.boot</groupId>
  <artifactId>mybatis-spring-boot-starter</artifactId>
  <version>2.1.1</version>
</dependency>

2）引入其他依赖

<dependencies>
<!-- web -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>

<!-- mysql -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>

<!-- swagger -->
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger2</artifactId>
<version>2.9.2</version>
</dependency>
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger-ui</artifactId>
<version>2.9.2</version>
</dependency>

<!-- Druid -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.21</version>
</dependency>

3）依赖图

三、用注解方式使用 MyBatis

1.准备创建department表的脚本

DROP TABLE IF EXISTS `department`;
CREATE TABLE `department` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`department_name` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

2.application.yml 自动执行脚本

initialization-mode: always
schema:
  - classpath:department.sql

执行一次后，注释 initialization-mode

# initialization-mode: always

3.创建department 实体类

package com.jackson0714.springboot.entity;
public class Department {    private Long id;    private String departmentName;
    public void setId(Long id) {        this.id = id;    }
    public Long getId() {        return id;    }
    public void setDepartmentName(String departmentName) {        this.departmentName = departmentName;    }
    public String getDepartmentName() {        return departmentName;    }}

4.创建Mapper映射类，并将SQL注解到方法上

增删改查，你要的都在这里：

@Mapperpublic interface DepartmentMapper {
    @Select("select * from department")    List<Map<String, Object>> getAllDepartment();
    @Select("select * from department where id=#{id}")    Department getDepartmentById(Long id);
    @Delete("delete from department where id=#{id}")    int deleteDepartment(Long id);
    @Insert("insert into department(department_name) values(#{departmentName})")    int createDepartment(String departmentName);
    @Update("update department set department_name=#{departmentName} where id=#{id}")    int updateDepartmentById(Long id, String departmentName);}

5.创建MyBatis 配置类

增加自定义配置：如果表的字段名有下划线格式的，转为驼峰命名格式

@org.springframework.context.annotation.Configurationpublic class MyBatisConfig {    @Bean    public ConfigurationCustomizer configurationCustomizer() {        return new ConfigurationCustomizer() {            @Override            public void customize(Configuration configuration) {                // 如果表的字段名有下划线格式的，转为驼峰命名格式                configuration.setMapUnderscoreToCamelCase(true);            }        };    }}

6.创建DepartmentController

@Api(value = "DepartmentController", description = "部门controller")@RequestMapping("/v1/client")@RestControllerpublic class DepartmentController {
    @Autowired    DepartmentMapper departmentMapper;
    @ApiOperation(value = "1.查询所有部门")    @GetMapping("/dept/getAllDepartment")    public List<Map<String, Object>> getAllDepartment() {        return departmentMapper.getAllDepartment();    }
    @ApiOperation(value = "2.根据id查询某个部门")    @ApiImplicitParams({            @ApiImplicitParam(name = "id", value = "需要查询的部门id")    })    @GetMapping("/dept/{id}")    public Department getDepartmentById(@PathVariable Long id) {        return departmentMapper.getDepartmentById(id);    }
    @ApiOperation(value = "3.新增部门")    @ApiImplicitParams({            @ApiImplicitParam(name = "name", value = "部门名称")    })    @PostMapping("/dept/create")    public int createDepartment(@RequestParam String name) {        return departmentMapper.createDepartment(name);    }
    @ApiOperation(value = "4.根据id删除部门")    @ApiImplicitParams({            @ApiImplicitParam(name = "id", value = "需要删除的部门id")    })    @PostMapping("/dept/delete")    public int deleteDepartment(@RequestParam Long id) {        return departmentMapper.deleteDepartment(id);    }
    @ApiOperation(value = "5.根据id更新部门名称")    @ApiImplicitParams({            @ApiImplicitParam(name = "id", value = "需要更新的部门id"),            @ApiImplicitParam(name = "name", value = "需要更新的部门名称")    })    @PostMapping("/dept/update")    public int updateDepartmentById(@RequestParam Long id, @RequestParam String name) {        return departmentMapper.updateDepartmentById(id, name);    }}

使用Swagger来测试

四、用配置方式使用 MyBatis

1. 文件结构

2. 创建user表的脚本

SET FOREIGN_KEY_CHECKS=0;
-- ------------------------------ Table structure for user-- ----------------------------DROP TABLE IF EXISTS `user`;CREATE TABLE `user` (  `user_id` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键ID',  `user_name` varchar(255) COLLATE utf8mb4_bin NOT NULL COMMENT '用户名',  `password` varchar(255) COLLATE utf8mb4_bin NOT NULL,  `salt` varchar(255) COLLATE utf8mb4_bin DEFAULT NULL COMMENT '随机盐',  `nickName` varchar(255) COLLATE utf8mb4_bin NOT NULL COMMENT '用户名',  `phone` varchar(20) COLLATE utf8mb4_bin DEFAULT NULL COMMENT '手机号',  `avatar` varchar(255) COLLATE utf8mb4_bin DEFAULT NULL COMMENT '头像',  `mini_openId`  varchar(32) COLLATE utf8mb4_bin DEFAULT NULL COMMENT '小程序OpenId',  `lock_flag` char(1) COLLATE utf8mb4_bin DEFAULT '0' COMMENT '0-正常，9-锁定',  `del_flag` char(1) COLLATE utf8mb4_bin DEFAULT '0' COMMENT '0-正常，1-删除',  `create_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',  `update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间',  PRIMARY KEY (`user_id`),  KEY `user_wx_openid` (`mini_openId`),  KEY `user_idx1_username` (`user_name`)) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci ROW_FORMAT=DYNAMIC COMMENT='用户表';

3. 插入一条User数据

INSERT INTO user(user_name, password, nick_name, phone) values ("jackson0714", "123", "悟空聊架构", "123456")

4. 创建User实体类

package com.jackson0714.springboot.entity;
import lombok.Data;
import java.sql.Timestamp;
@Datapublic class User {
    private Long userId;    private String userName;    private String password;    private String salt;    private String nickName;    private String phone;    private String avatar;    private String miniOpenId;    private String openId;    private Boolean lockFlag;    private Boolean delFlag;    private Timestamp createTime;    private Timestamp updateTime;}

需要安装Lombok插件

需要引入Lombok依赖

<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
<dependency>
  <groupId>org.projectlombok</groupId>
  <artifactId>lombok</artifactId>
  <version>1.18.12</version>
  <scope>provided</scope>
</dependency>

5. 创建调用User方法的 UserMapper 接口

// @Mapper 或MapperScan 将接口扫描装配到装配容器中
public interface UserMapper {
User getUserById(Long userId);
}

6. 创建接口方法与SQL脚本的映射文件

<?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.jackson0714.springboot.mapper.UserMapper">
    <select id="getUserById" resultType="com.jackson0714.springboot.entity.User">
        SELECT * FROM user WHERE user_id=#{userId}
    </select>
</mapper>

7. 创建UserController文件

@Api(value = "UserController", description = "用户controller")@RequestMapping("/v1/client")@RestControllerpublic class UserController {
    @Autowired    UserMapper userMapper;
    @ApiOperation(value = "1.根据id查询某个用户")    @ApiImplicitParams({            @ApiImplicitParam(name = "需要查询的用户userId", value = "需要查询的用户userId")    })    @GetMapping("/emp/{userId}")    public User getUser(@PathVariable("userId") Long userId) {        return userMapper.getUserById(userId);    }}

8. 添加MapperScan注解

@MapperScan(value = "com.jackson0714.springboot.mapper")@SpringBootApplicationpublic class Springboot07DataMybatisApplication {    public static void main(String[] args) {        SpringApplication.run(Springboot07DataMybatisApplication.class, args);    }}