Mybatis源码解析1：环境搭建

1.项目结构

github老是打不开，直接贴代码吧

2.pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.lmh.example</groupId>
    <artifactId>mybatis-plugin</artifactId>
    <version>1.0-SNAPSHOT</version>
    <description>Mybatis拦截器插件</description>

    <profiles>
        <profile>
            <id>jdk-1.8</id>
            <activation>
                <activeByDefault>true</activeByDefault>
                <jdk>1.8</jdk>
            </activation>
            <properties>
                <maven.compiler.source>1.8</maven.compiler.source>
                <maven.compiler.target>1.8</maven.compiler.target>
                <maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion>
            </properties>
        </profile>
    </profiles>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.4</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.21</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.79</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.21</version>
        </dependency>

        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.24</version>
        </dependency>
    </dependencies>
</project>

3.table.sql

-- 工厂表，每个工厂的负责人，负责维护工厂的信息
CREATE TABLE `Blog` (
  `id` bigint NOT NULL AUTO_INCREMENT COMMENT '主键id',
  `name` varchar(255) DEFAULT NULL COMMENT '工厂名称',
  `address` varchar(255) DEFAULT NULL COMMENT '用户信息'
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

4. mybatis-config

<?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>
    
    <plugins>
        <plugin interceptor="com.lmh.mybatis.plugin.interceptor.MyInterceptor"/>
    </plugins>

    <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/test?serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="mapper/Blog.xml"/>
    </mappers>

</configuration>

5.Blog

@Data
public class Blog {
   

    private Long id;

    private String name;

    private String address;
}

6.BlogMapper

public interface BlogMapper {
   

    Blog selectById(@Param("id") Long id);

}

7.BlogMapper.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="com.lmh.mybatis.plugin.mapper.BlogMapper">
    
    <select id="selectById" resultType="com.lmh.mybatis.plugin.entity.Blog">
        select id, name, address from blog where id = #{id}
    </select>

</mapper>

8.MyInterceptor

@Slf4j
@Intercepts(@Signature(type = StatementHandler.class, method = "query", args = {
   Statement.class, ResultHandler.class}))
public class MyInterceptor implements Interceptor {
   

    /**
     * 拦截器调用执行的逻辑
     */
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
   
        log.info("Process interceptor for query method...");
        return invocation.proceed();
    }

    /**
     * 注册拦截器，父类 已注册
     */
    @Override
    public Object plugin(Object target) {
   
        return Plugin.wrap(target, this);
    }

    /**
     * 设置属性
     */
    @Override
    public void setProperties(Properties properties) {
   

    }
}

9. InterceptorTest

/**
 * 测试类
 */
@Slf4j
public class InterceptorTest {
   

    public static void main(String[] args) throws IOException {
   
        //获取文件配置流
        InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
        //创建SqlSessionFactoryBuilder对象
        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
        //通过SqlSessionFactoryBuilder对象解析配置文件，config.xml和mapper.xml
        //解析到的mapper.xml文件会创建Statement对象，并且注册到Configuration#mappedStatements
        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
        //通过sqlSessionFactory创建SqlSession，根据解析到mapper.xml获取Sql的类型，创建执行器
        //这里还会对执行起来Executor进行代理，最终封装在DefaultSqlSession对象里面
        try(SqlSession sqlSession = sqlSessionFactory.openSession()) {
   
            //通过SqlSession获取到指定的Mapper，实际返回的是JDK代理对象
            BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);
            Blog blog = mapper.selectById(1L);
            log.error(JSON.toJSONString(blog));
        }

    }
}