Mybatis阅读源码的前置准备工作

版本信息

Spring Boot 3.3.0
Mybatis 3.5.16
JDK 17

Demo搭建

搭建一个简单的Spring Boot项目，方便调试Mybatis源码。

首先创建一个Spring Boot的项目，我这里将项目命名为Mybatis_Reader，并引入相关依赖。

设置依赖

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

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.mybatis.spring.boot/mybatis-spring-boot-starter -->
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>3.0.3</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-logging</artifactId>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.16</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/com.mysql/mysql-connector-j -->
    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <version>8.4.0</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
    </dependency>
</dependencies>

yml配置

创建application.yml，并添加以下内容：

# 配置数据源
spring:
  application:
    name: Mybatis_Reader
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/blog_db?useUnicode=true&characterEncoding=utf-8
    username: root
    password: 123456
mybatis:
  config-location: classpath:mybatis-config.xml

Mybatis配置类

在resources文件夹中创建mybatis-config.xml，并填充内容

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="TRUE"/>
    </settings>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/blog_db"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <!-- Register mapper files -->
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>

</configuration>

日志文件配置

创建logback.xml，以自定义输出日志信息，内容简单点就行：

<configuration>
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>

    <root level="DEBUG">
        <appender-ref ref="STDOUT" />
    </root>

    <logger name="org.apache.ibatis" level="DEBUG" additivity="false">
        <appender-ref ref="STDOUT" />
    </logger>
</configuration>

表结构

数据库中创建一张用户表用来做测试

CREATE TABLE `T_USER` (
  `id` bigint NOT NULL AUTO_INCREMENT,
  `USER_NAME` varchar(45) DEFAULT NULL COMMENT '姓名',
  `AGE` int DEFAULT NULL COMMENT '年龄',
  `GENDER` int DEFAULT NULL COMMENT '性别',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci COMMENT='用户主表'

创建相关的类

项目中创建一个mybatis的包，然后创建相关的类

JDBCConstant.java

public class JDBCConstant {
    public static final String URL = "jdbc:mysql://localhost:3306/blog_db?useUnicode=true&characterEncoding=utf-8";
    public static final String USERNAME = "root";
    public static final String PASSWORD = "123456";
}

UserPO.java

@Data
public class UserPO implements Serializable {

    private Long id;

    private String userName;

    private Integer gender;
    
}

UserMapper.java

@Mapper
@CacheNamespace
public interface UserMapper {

    @Select("SELECT * FROM T_USER WHERE id = #{id}")
    @Options
    UserPO selectUserById(Long id);

    @Update("UPDATE T_USER SET USER_NAME = #{arg0} WHERE id = #{arg1}")
    int updateUserNameById(Long id, String name);

    List<UserPO> queryUserList();
}

自定义SQL

resources中创建一个mapper文件夹，用以放置编写自定义SQL的XML文件。

UserMapper.xml

<?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="org.example.mybatis_reader.mybatis.UserMapper">
    <select id="queryUserList" resultType="org.example.mybatis_reader.mybatis.UserPO">
        SELECT * FROM T_USER
    </select>
</mapper>