1.准备工作

1.1 准备数据库

数据库

1.2 准备与数据库表对应的pojo类

User：

public class User implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private Integer id;
    private String username;// 用户姓名
    private String sex;// 性别
    private Date birthday;// 生日
    private String address;// 地址


    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", sex=" + sex
                + ", birthday=" + birthday + ", address=" + address + "]";
    }
}

2.配置文件

2.1 mybaits配置文件

sqlMapConfig.xml：

引入了所有的pojo类对应的xml mapping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>
    <!-- 和spring整合后 environments配置将废除    -->
    <environments default="development">
        <environment id="development">
            <!-- 使用jdbc事务管理 -->
            <transactionManager type="JDBC" />
            <!-- 数据库连接池 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url"
                          value="jdbc:mysql://localhost:3306/mybaits?characterEncoding=utf-8" />
                <property name="username" value="root" />
                <property name="password" value="123456" />
            </dataSource>
        </environment>
    </environments>

    <!-- Mapper的位置  Mapper.xml 写Sql语句的文件的位置 （resource、class、url只能有一个，不能同时存在）-->
    <mappers>
                <mapper resource="mybaits/sqlmap/User.xml"/>
        <!--        <mapper resource="sqlmap/User.xml" class="" url=""/> -->
        <!--        <mapper class="com.itheima.mybatis.mapper.UserMapper" /> -->
        <!--        <mapper url="" /> -->
        <!--<package name="mybaits.sqlmap"/>-->
    </mappers>
</configuration>

2.2 pojo类对应的mapping配置文件

User.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">

<!--命名空间：可以防止多个mapping文件都有同一个方法时的混乱问题，通过命名空间.方法名解决，比如user.findUserById-->
<mapper namespace="user">
    <!--parameterType:入参类型，限制调用者使用时需要传参user.findUserById(int)-->
    <!--resultType:返回值类型，调用者调用user.findUserById(int)这个方法以后会返回一个User对象-->
    <select id="findUserById" parameterType="Integer" resultType="mybaits.pojo.User">
        <!--#{}是mybaits占位符，jdbc占位符是？。-->
        <!--value是引用传进来的inter值，这个名称任意，可以叫value，也可写任意字符-->
        SELECT * FROM user WHERE id = #{value}
    </select>
</mapper>

3 调用

package mybaits.junit;

import mybaits.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class Test {

    @org.junit.Test
    public void testMybaits() throws IOException {

        //加载核心配置文件
        String resource = "sqlMapConfig.xml";
        InputStream in = Resources.getResourceAsStream(resource);
        //创建SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //创建SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //执行Sql语句
        User user = sqlSession.selectOne("user.findUserById", 10);

        System.out.println(user);
    }
}

4 其他查询

4.1 用户名模糊查询

mapping：

    <!--调用这希望的返回值是一个list<User>,但是这边resultType只需要写List的形参User即可-->
    <select id="findUserByUsername" parameterType="String" resultType="mybaits.pojo.User">
        <!-- 这里的value只可以写value，不能写成其他的值 -->
        <!-- ${value}指代的就是传进来的username，比如张三，这里就是SELECT * FROM user WHERE username LIKE '%张三%'
        而如果是写#{value}的话，这里就变成了SELECT * FROM user WHERE username LIKE '%'张三'%'-->
        SELECT * FROM user WHERE username LIKE '%${value}%'
    </select>

调用者：

    @org.junit.Test
    public void testMybaits2() throws IOException {

        //加载核心配置文件
        String resource = "sqlMapConfig.xml";
        InputStream in = Resources.getResourceAsStream(resource);
        //创建SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //创建SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //执行Sql语句
        List<User> list = sqlSession.selectList("user.findUserByUsername", "张三");

        for (User user:list) {
            System.out.println(user);
        }
    }

4.2 插入数据

mapping：

    <insert id="insertUser" parameterType="mybaits.pojo.User">
        <!--只要username这些和User类里面的字段匹配好，虽然传进来的是mybaits.pojo.User，但是可以直接#{username}这样引用-->
        INSERT INTO user (username,birthday,address,sex) VALUES (#{username},#{birthday},#{address},#{sex})
    </insert>

调用者：

    @org.junit.Test
    public void testMybaits3() throws IOException {

        //加载核心配置文件
        String resource = "sqlMapConfig.xml";
        InputStream in = Resources.getResourceAsStream(resource);
        //创建SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //创建SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        User user = new User();
        user.setSex("男");
        user.setUsername("California");

        //执行Sql语句
        int result = sqlSession.insert("user.insertUser", user);
        System.out.println(result);
        //如果不commit就不可以插入成功
        sqlSession.commit();
    }

4.3 更新数据

mapping：

    <update id="updateUserById" parameterType="mybaits.pojo.User">
        UPDATE user SET username = #{username} WHERE id = #{id}
    </update>

调用者：

    @org.junit.Test
    public void testMybaits4() throws IOException {

        //加载核心配置文件
        String resource = "sqlMapConfig.xml";
        InputStream in = Resources.getResourceAsStream(resource);
        //创建SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //创建SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        User user = new User();
        user.setId(31);
        user.setSex("男");
        user.setUsername("tom");

        //执行Sql语句
        int result = sqlSession.update("user.updateUserById", user);

        //如果不commit就不可以插入成功
        sqlSession.commit();
        System.out.println(result);
    }

4.4 删除数据

mapping：

    <delete id="deleteUserById" parameterType="mybaits.pojo.User">
        DELETE FROM user WHERE id = #{id}
    </delete>

调用者：

    @org.junit.Test
    public void testMybaits5() throws IOException {

        //加载核心配置文件
        String resource = "sqlMapConfig.xml";
        InputStream in = Resources.getResourceAsStream(resource);
        //创建SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //创建SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        User user = new User();
        user.setId(30);
        user.setSex("男");
        user.setUsername("tom");

        //执行Sql语句
        int result = sqlSession.delete("user.deleteUserById", user);

        //如果不commit就不可以插入成功
        sqlSession.commit();
        System.out.println(result);
    }