【mybatis入门】

mybatis的入门之搭建mybatis框架：

第一步：在resources包下建立db.properties数据库连接数据

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=utf-8
username=root
password=root

第二步：从官方文档复制配置文件（放在resources报下，并填写对应的driver、url、username、password）

<?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="${driver}"/>
        <property name="url" value="${url}"/>
        <property name="username" value="${username}"/>
        <property name="password" value="${password}"/>
      </dataSource>
    </environment>
  </environments>
  <mappers>
    <mapper resource="org/mybatis/example/BlogMapper.xml"/>
  </mappers>
</configuration>

第三部：创建对应的工具类：

public class MybatisUtil {
private static SqlSessionFactory sqlSessionFactory;

    static {
        String resources = "mybatis-config.xml";
        //获取sqlSessionFactory对象
        try {
            InputStream inputStream = Resources.getResourceAsStream(resources);
             sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }


    }
    public static SqlSession getSqlSession(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }
}

第四步：写实体类

public class Users {
private int id;
private String name;
private String pwd;

    public Users(int id) {
        this.id = id;
    }

    public Users(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "Users{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

第五步：写接口及UsersMapper.xml
 

public interface UsersDao {
    public List<Users> getUsersList();

    //
    Users getUserById(int id);
}

<!--select id,name,password as pwd from mybatis.users where id = #{id}-->
<mapper namespace="com.dao.UsersDao">
<!--结果集映射
resultMap 元素是 MyBatis 中最重要最强大的元素-->
    <resultMap id="UsersMap" type="Users">
<!-- column=""=数据库的字段  property=""=实体类中的属性     -->
<!--        <result column="id" property="id"/>-->
<!--        <result column="name" property="name"/>-->
        <result column="password" property="pwd"/> 
    </resultMap>
    <select id="getUsersList" resultType="Users">
       select * from mybatis.users;
    </select>
    <select id="getUserById" resultType="Users">
        select * from mybatis.users where id = #{id};
    </select>

</mapper>

第六步：写测试类测试（测试类建议放在test包下并且跟main包一一对应）

 @Test
    public void test(){
        //获得sqlSession对象
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        //执行SQL
        UsersMapper mapper = sqlSession.getMapper(UsersMapper.class);
        List<Users> usersList = mapper.getUsersList();
        //方式二：
//        List<Users> usersList = sqlSession.selectList("com.Util.dao.UsersDao.getUsersList");
        for (Users users : usersList) {
            System.out.println(users);
        }
        //关闭sqlSession
        sqlSession.close();

    }