一、Mybatis的入门。

（1）Mybatis的简介。

Mybatis是一个持久层框架。

（2）Mybatis的快速入门。

（2.1）快速入门。

（2.2）UserMapper.xml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="userMapper"><select id="findAll" resultType="domain.User">select * from user</select>
</mapper>

（2.3）sqlMapConfig.xml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><!--数据源环境--><environments default="development"><!--默认使用下面id为development的环境--><environment id="development"><transactionManager type="JDBC"></transactionManager><dataSource type="POOLED"><property name="driver" value="com.mysql.cj.jdbc.Driver"/><property name="url" value="jdbc:mysql://localhost:3306/test"/><property name="username" value="root"/><property name="password" value="tan"/></dataSource></environment></environments><!--加载映射文件--><mappers><mapper resource="mapper/UserMapper.xml"></mapper></mappers>
</configuration>

（2.4）测试类代码。

package test;
public class MyBatisTest {@Testpublic void test1() throws IOException {//1.获取核心配置文件InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");//2.获得session工厂对象SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);//3.获取session会话对象SqlSession sqlSession = sqlSessionFactory.openSession();//4.执行操作List<User> userList = sqlSession.selectList("userMapper.findAll");//5.打印数据System.out.println(userList);//6.释放资源sqlSession.close();}
}

（3）MyBatis的映射文件概述。

（4）MyBatis的增删改查操作。

（4.1）查询操作。

<?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="userMapper"><!--1、查询操作--><select id="findAll" resultType="domain.User">select * from user</select><!--2、插入操作--><insert id="save" parameterType="domain.User">insert into user values (#{id},#{username},#{password})</insert><!--3、修改操作--><update id="update" parameterType="domain.User">update user set username=#{username},password=#{password} where id = #{id}</update><!--4、删除操作--><delete id="delete" parameterType="java.lang.Integer">delete from user where id = #{id}</delete>
</mapper>

    @Test//查询操作public void test1() throws IOException {//1.获取核心配置文件InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");//2.获得session工厂对象SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);//3.获取session会话对象SqlSession sqlSession = sqlSessionFactory.openSession();//4.执行操作List<User> userList = sqlSession.selectList("userMapper.findAll");//5.打印数据System.out.println(userList);//6.释放资源sqlSession.close();}

（4.2）插入操作。

<?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="userMapper"><!--2、插入操作--><insert id="save" parameterType="domain.User">insert into user values (#{id},#{username},#{password})</insert>
</mapper>

    @Test//插入操作public void test2() throws IOException {//模拟user对象User user = new User();//user.setId(-1);//设置为0（不设置，默认为0）则自增，设置其他不自增（负数，整数，导致都不会自增）user.setUsername("asss");user.setPassword("abc");//1.获取核心配置文件InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");//2.获得session工厂对象SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);//3.获取session会话对象SqlSession sqlSession = sqlSessionFactory.openSession();//4.执行操作 参数：namespace+id（命名空间.id）sqlSession.insert("userMapper.save",user);//5.mybatis执行更新操作，提交事务sqlSession.commit();//6.释放资源sqlSession.close();}

（4.3）修改操作。

<?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="userMapper"><!--3、修改操作--><update id="update" parameterType="domain.User">update user set username=#{username},password=#{password} where id = #{id}</update>
</mapper>

    @Test//修改操作public void test3() throws IOException {//模拟user对象User user = new User();user.setId(-1);user.setUsername("lucy");user.setPassword("123");//1.获取核心配置文件InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");//2.获得session工厂对象SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);//3.获取session会话对象SqlSession sqlSession = sqlSessionFactory.openSession();//4.执行操作 参数：namespace+id（命名空间.id）sqlSession.update("userMapper.update",user);//5.mybatis执行更新操作，提交事务sqlSession.commit();//6.释放资源sqlSession.close();}

（4.4）删除操作。

<?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="userMapper"><!--4、删除操作--><delete id="delete" parameterType="java.lang.Integer">delete from user where id = #{id}</delete>
</mapper>

    @Test//删除操作public void test4() throws IOException {//1.获取核心配置文件InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");//2.获得session工厂对象SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);//3.获取session会话对象SqlSession sqlSession = sqlSessionFactory.openSession();//4.执行操作 参数：namespace+id（命名空间.id）sqlSession.delete("userMapper.delete",8);//5.mybatis执行更新操作，提交事务sqlSession.commit();//6.释放资源sqlSession.close();}