由浅入深--第一个MyBatis程序

　　话不多说，马上开始我们的第一个Mybatis程序；

　　第一个程序，当然要参考MyBatis的官网文档来搞，地址如下：https://mybatis.org/mybatis-3/zh/getting-started.html；

　　第一个程序，源代码托管在github，地址如下：https://github.com/gdoujkzz/MybatisDemo 的FirstDemo；

　 我的第一个MyBatis程序

　　第一步：先创建Maven工程，引入Mybatis；

　　第二步：在数据库中创建表和插入数据，脚本如下：

create table Test_User(
    Id number(10) primary key,
    Name varchar2(50) not null
)

insert into Test_User(id,name) values(1,'张三');
insert into Test_User(id,name) values(2,'李四');
insert into Test_User(id,name) values(3,'王五');
insert into Test_User(id,name) values(4,'赵六');

　　第三步：创建和数据库对应的POJO类；

public class User implements Serializable {

    private Integer id;

    private String name;

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("User{");
        sb.append("id=").append(id);
        sb.append(", name='").append(name).append('\'');
        sb.append('}');
        return sb.toString();
    }
}

　　第四步 编写全局的配置文件

<?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="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="oracle.jdbc.OracleDriver"/>
                <property name="url" value="jdbc:oracle:thin:@//www.test.com:1601/mestst9"/>
                <property name="username" value="mespro"/>
                <property name="password" value="mesprotst123"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/TestUserMapper.xml"></mapper>
    </mappers>
</configuration>

　　第五步 编写映射文件

<?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="mapper/TestUserMapper">

    <select id="selectUser" resultType="com.gdou.mes.User">
        select * from test_user
    </select>

    <select id="selectUserById" resultType="com.gdou.mes.User">
        select * from test_user where id=#{id}
    </select>

</mapper>

　　第六步 加载配置文件并开始操作

public class UserMapperTest {

    private SqlSessionFactory factory;

    @Before
    public void SetUp() throws Exception {
        InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
        factory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    /**
     * Rigorous Test :-)
     */
    @Test
    public void selectTest() throws Exception {
        SqlSession session = factory.openSession();
        try {
            //查询所有数据
            System.out.println("--------------查询所有数据开始-------------------");
            List<User> list = session.selectList("mapper/TestUserMapper.selectUser");
            for (User user : list) {
                System.out.println(user);
            }
            System.out.println("--------------查询所有数据结束-------------------");
            //查询单条数据
            System.out.println("---------------查询单条数据开始-------------------");
            User user = session.selectOne("mapper/TestUserMapper.selectUserById", 1);
            System.out.println(user);
            System.out.println("---------------查询单条数据结束-------------------");
        } catch (Exception ex) {
            System.out.println(ex);
        } finally {
            session.close();
        }
    }
}