myBatis入门

一概述

二入门代码

1.环境

(1)jar包
mysql数据库驱动包
myBatis相关jar包

(2)配置文件
log4j.properties
SqlMapConfig.xml     核心配置文件
user.xml             表映射配置文件  写数据库语句
(3)其他
数据库表的pojo类（字段对应）

配置文件注意事项：
核心配置配置文件中要导入sql映射文件()
<mappers>
<mapper resource="sqlmap/User.xml"/>
</mappers>

2.代码

package com.itheima.test;

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

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 com.itheima.domain.User;

public class MyBatisTest {
public static void main(String[] args) throws Exception {
//1.获得sqlSession对象
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml"); //Resouces是Mybatis提供的工具类
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();

//2.调用相关方法完成业务操作
User user = sqlSession.selectOne("findUserById", 1); //正好对应<select id="" parameterType="" resultType="">select * from user where id = #{id}</select>
System.out.println(user); //注意#{}相当于占位符

//3.释放资源 , 每一个sqlSession就是一个连接
sqlSession.close();
}
}

<?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/mybatis?characterEncoding=utf-8" />
<property name="username" value="root" />
<property name="password" value="root" />
</dataSource>
</environment>
</environments>

<mappers>
<!--将Users.xml添加在SqlMapConfig.xml  -->
<mapper resource="sqlmap/User.xml"/>
</mappers>
</configuration>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
P
4000
UBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="test">
<!-- id为sql语句的id，parameterType 参数类型 ， resultType 返回的类型 (实体类要写类全名)-->
<select id="findUserById" parameterType="int" resultType="com.itheima.domain.User">
SELECT * from user where id= #{id}
</select>

</mapper>