mybatis源码简单分析

mybatis入门介绍

/**
 * 1. 接口式编程
 *      原生: Dao =====> DaoImpl
 *      mybatis : Mapper =====> xxxMapper
 * 2. SqlSession 代表数据库的一次会话, 用完需要关闭会话
 * 3. SqlSession 和 Connection 一样都是线程不安全的, 所以不能放在堆区(类成员对象), 所以每次创建都应该是新的对象
 * 4. mapper接口没有实现类, 但是mybatis会为其创建代理对象
 *      将接口和xml进行绑定
 *      EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
 *
 */
public class MybatisTest {

    /**
     * 旧方式
     */
    @Test
    public void test() {
        SqlSession sqlSession = null;
        String resource = "SqlMapConfig.xml";
        try (
                InputStream inputStream = Resources.getResourceAsStream(resource);
        ) {
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            sqlSession = sqlSessionFactory.openSession();
            Employee employee = sqlSession.selectOne("com.zhazha.mybatis.bean.Employee.selectBlog", 1);
            System.out.println(employee);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (null != sqlSession) {
                sqlSession.close();
            }
        }
    }

    /**
     * 新方式
     * @throws IOException
     */
    @Test
    public void test1() throws IOException {
        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = factory.openSession();
        EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
        Employee employee = mapper.get(1);
        System.out.println(employee);
        sqlSession.close();
    }
}

旧方式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.zhazha.mybatis.bean.Employee">
    <select id="selectBlog" resultType="com.zhazha.mybatis.bean.Employee">
        SELECT te.id, te.last_name AS  lastName, te.email, te.gender FROM tbl_employee te WHERE te.id = #{id}
    </select>
</mapper>

新方式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接口 -->
<mapper namespace="com.zhazha.mapper.EmployeeMapper">
    <!-- get mapper方法的函数名称 -->
    <select id="get" resultType="com.zhazha.mybatis.bean.Employee">
        SELECT te.id, te.last_name AS  lastName, te.email, te.gender FROM tbl_employee te WHERE te.id = #{id}
    </select>
</mapper>

mybatis的sql映射文件

<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="EmployeeMapper.xml" />
        <mapper resource="Employee.xml" />
    </mappers>
</configuration>

log4Jxml配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
 
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
 
 <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
   <param name="Encoding" value="UTF-8" />
   <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m  (%F:%L) \n" />
   </layout>
 </appender>
 <logger name="java.sql">
   <level value="debug" />
 </logger>
 <logger name="org.apache.ibatis">
   <level value="info" />
 </logger>
 <root>
   <level value="debug" />
   <appender-ref ref="STDOUT" />
 </root>
</log4j:configuration>