springboot整合mybatis

• 准备数据库表

CREATE TABLE `t_user` (
  `id` int NOT NULL AUTO_INCREMENT COMMENT '主键',
  `name` varchar(255) DEFAULT NULL COMMENT '姓名',
  `age` int DEFAULT NULL COMMENT '年龄',
  `gender` varchar(255) DEFAULT NULL COMMENT '性别',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb3;

• 新建boot项目，pom.xml导入依赖

	<dependencies>
        <!--web依赖-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!--mysql依赖-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--mybatis整合springboot框架依赖-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.0</version>
        </dependency>
        <!--测试依赖-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <!--打包xml文件-->
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
        <!--打包插件-->
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

• 创建实体类

public class User {
    private Integer id;
    private String name;
    private Integer age;
    private String gender;
    //省略了get/set方法
}

• 创建对应的mapper接口和映射文件

public interface UserMapper {

    /**
     * 根据姓名模糊查询用户信息
     * @date 2022/3/27 9:05
     * @param user
     * @return java.util.List<com.example.bootmybatis.entity.User>
     */
    List<User> selectUserInfo(User user);
}

<?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.bootmybatis.mapper.UserMapper">
    <resultMap id="BaseResultMap" type="com.example.bootmybatis.entity.User">
        <id column="id" property="id"/>
        <result column="name" property="name"/>
        <result column="age" property="age"/>
        <result column="gender" property="gender"/>
    </resultMap>
    
    <sql id="Base_Column_List">
        id,name,age,gender
    </sql>

    <select id="selectUserInfo" resultType="com.example.bootmybatis.entity.User">
        select <include refid="Base_Column_List"/> from t_user
        <where>
            <if test="name != null and name != ''">
                name like concat('%',#{name},'%')
            </if>
            <if test="age != null and age != ''">
                and age=#{age}
            </if>
            <if test="gender != null and gender != ''">
                and gender=#{gender}
            </if>
        </where>
    </select>
</mapper>

• 控制层代码

@RestController
public class UserController {

    @Autowired
    private UserService userService;

    @PostMapping(value = "/selectUserInfo")
    public List<User> selectByIdUserInfo(@RequestBody User user){
        List<User> users = userService.selectUserInfo(user);
        return users;
    }
}

• 项目启动类上添加扫描mapper文件注解

@SpringBootApplication
@MapperScan(basePackages = "com.example.bootmybatis.mapper") // 开启扫描mapper
public class BootMybatisApplication {
    public static void main(String[] args) {
        SpringApplication.run(BootMybatisApplication.class, args);
    }
}

• 配置数据库连接

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/springboot?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
    username: root
    password: root
mybatis:
  type-aliases-package: com.example.bootmybatis.entity #配置XML映射文件中指定的实体类别名路径
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl #打印sql语句日志

• 启动项目，访问控制层路径
  

上面mapper接口和映射文件是在src/main/java相同目录下面，在pom.xml文件中配置了下面配置，启动项目打包的时候就会将xml文件打包进去。

 <!--打包xml文件-->
 <resources>
     <resource>
         <directory>src/main/java</directory>
         <includes>
             <include>**/*.xml</include>
         </includes>
         <filtering>false</filtering>
     </resource>
 </resources>

除了这种写法之外，还有另外一个常见的写法，将映射文件放到类路径下的resource目录下面，如果是这种写法就要在yaml核心配置文件中配置如下配置，告诉mapper映射文件的位置。

mybatis:
  mapper-locations: classpath:mapper/*.xml #配置MyBatis的xml配置文件路径