MyBatis 实用篇（一）入门

MyBatis 实用篇（一）入门

MyBatis(http://www.mybatis.org/mybatis-3/zh/index.html) 是一款优秀的持久层框架，它支持定制化 SQL、存储过程以及高级映射。

MyBatis 消除了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。

MyBatis 可以使用简单的 XML 或注解来配置和映射原生信息，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。

1. 引入 MyBatis

<dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.4.6</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.32</version>
    </dependency>
</dependencies>

2. 配置文件

<?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="dev">
        <environment id="dev">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com/github/binarylei/mybatis/helloworld/UserMapper.xml"/>
    </mappers>
</configuration>

3. mapper 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.github.binarylei.mybatis.helloworld.UserMapper">
    <select id="getUser" resultType="com.github.binarylei.mybatis.helloworld.User">
        select * from user where id=#{id};
    </select>
</mapper>

4. 使用

4.1 xml 调用

public void test() {
    Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
    SqlSession sqlSession = sqlSessionFactory.openSession();
    try {
        User user = sqlSession.selectOne("getUser", 1);
        System.out.println(user);
    } finally {
        sqlSession.close();
    }
}

4.2 接口调用

public interface UserMapper {
    void getUser(User user);
}

public void test() {
    Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
    SqlSession sqlSession = sqlSessionFactory.openSession();
    try {
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = (User) userMapper.getUser(1);
        System.out.println(user);
    } finally {
        sqlSession.close();
    }
}

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每天用心记录一点点。内容也许不重要，但习惯很重要！