mybatis学习笔记

一、mybatis简介

mybatis是apache下的一个顶级开源项目，原名ibatis,项目源2010年由apache软件基金会迁移到google code并改名mybatis,2013年迁移到github;mybatis是一个持久层框架
学习mybatis中文手册：https://mybatis.org/mybatis-3/zh/index.html

二、mybatis入门

入门步骤：

1. 创建一个maven工程
2. 导入mybatis及其相应的jar包
3. 编写mabatis核心配置文件
4. 编写映射文件mapper
5. 把映射文件在核心配置文件中加载
6. 编码，实现通过mybatis得到数据

• 导入mybatis及其相应的jar包

<dependencies>
		<!-- mybatis -->
		<dependency>
			<groupId>org.mybatis</groupId>
			<artifactId>mybatis</artifactId>
			<version>3.5.7</version>
		</dependency>
		<!-- junit -->
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.12</version>
			<scope>test</scope>
		</dependency>
		<!-- mysql -->
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>8.0.21</version>
		</dependency>
	</dependencies>

• 编写mabatis核心配置文件

<?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"/>
      <dataSource type="POOLED">
	      <!-- 配置数据库 -->
        <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3308/user_db?serverTimezone=UTC"/>
        <property name="username" value="root"/>
        <property name="password" value="huang"/>
      </dataSource>
    </environment>
  </environments>
  <mappers>
   	 <!-- 加载映射文件 -->
   	<mapper resource="userMapping.xml"/>
  </mappers>
</configuration>

• 编写映射文件mapper

<?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="ns">
	<!-- 查找单个数据 -->
	<select id="get" parameterType="int" resultType="cn.entity.User">
		select *from
		tb_users where uid=#{uid}
	</select>
	<!-- 查找全部数据 -->
	<select id="selectAllUser" resultType="cn.entity.User">
		select *from tb_users
		limit 0,5
	</select>
	<!-- 修改 -->
	<update id="toUpdate" parameterType="cn.entity.User">
		UPDATE tb_users
		SET
		uloginid = #{uloginid },
		upassword =#{upassword },
		utel = #{utel },
		uaddress = #{uaddress },
		uname = #{uname },
		uemail =
		#{uemail },
		deptno = #{deptno },
		udate = #{udate },
		ustateid = #{ustateid
		}
		<!--uid要与uid对得上 -->
		WHERE uid = #{uid};

	</update>
	<delete id="delectUser" parameterType="int">
		DELETE from tb_users
		WHERE uid = #{uid};


	</delete>
	<insert id="insertUser" parameterType="cn.entity.User">
		INSERT INTO tb_users
		(uloginid,
		upassword,
		utel,
		uaddress,
		uname,
		uemail,
		deptno,
		udate,
		ustateid)
		VALUES
		(
		#{uloginid },
		#{upassword },
		#{utel },
		#{uaddress },
		#{uname },
		#{uemail },
		#{deptno },
		#{udate },
		#{ustateid });

	</insert>
    <select id="likeUser" parameterType="String" resultType="cn.entity.User">
       select *from tb_users where uname like '%${value}%'
    </select>
</mapper>

• 编码，实现通过mybatis得到数据

  @Test
  public void dogetTest() throws IOException {
	  //读取核心配置文件
	 String resource ="mybatis-config.xml";
	 InputStream resourceAsStream = Resources.getResourceAsStream(resource);
	 //创建sqlSession工厂
	 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
	 //得到sqlsession对象
	 SqlSession session = sqlSessionFactory.openSession();
	 //获取sql数据
	 User selectOne = session.selectOne("ns.get",1);
     System.out.println(selectOne);
     session.close();
  }