Mybatis分析（1）-SqlSessionFactory

SqlSessionFactory

• 首先理解mybatis的原理，并不是从spring的集成开始。而每一个mybatis的应用程序都是由SqlSessionFactory为核心开始，而SqlSessionFactory又是由SqlSessionFactoryBuilder对象获取而来。
  SqlSessionFactoryBuilder可以从XML配置文件中加载配置信息从而创建SqlSessionFactory。
  demo例子：
  MybatisHelloWorld:

public class MybatisHelloWorld {

    public static void main(String[] args) throws Exception{
        String resource = "src/main/resource/Configuration.xml";
        FileInputStream file = new FileInputStream(resource);
        Reader reader = new InputStreamReader(file);
        try {
            SqlSessionFactory sqlMapper = new SqlSessionFactoryBuilder().build(reader);
            SqlSession session = sqlMapper.openSession();
            try {
                UserVo user = (UserVo) session.selectOne("com.hhd.mybatis.repository.UserMapper.getUser", "1");
                System.out.println(user.getId() + "," + user.getName());
            } finally {
                session.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

UserMapper：

<?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.hhd.mybatis.repository.UserMapper">
    <select id="getUser" parameterType="String" resultType="com.hhd.mybatis.vo.UserVo">
        select id,name from user where id = #{id}
    </select>
</mapper>

UserMapper:

public interface UserMapper {

   UserVo getUser(String id);
}

UserVo:

public class UserVo implements Serializable {

    private String id;

    private String name;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Configuration.xml

<?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://#########.3:10001/mybatis?useUnicode=true"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/hhd/mybatis/mapper/UserMapper.xml"/>
    </mappers>
</configuration>

• 运行结果

  
  image.png

• 可以看出SqlSessionFactoryBuilder是整个入口的核心类，他主要承担了mybatis的配置文件的加载，解析，以及内部构建等职责。