#千锋逆战# Mybatis基础(1)

pom.xml依赖导入

<!--测试-->
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
</dependency>
<!--mybatis-->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.4.6</version>
</dependency>
<!--mysql-->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.25</version>
</dependency>

在resource下新建mybatis.xml

<?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">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="org/mybatis/example/BlogMapper.xml"/>
    </mappers>
</configuration>

创建pojo以对应的xml文件,namespace可以自定义,id也可以自定义,但必须唯一,resultType定义结果类型

<?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="org.mybatis.example.BlogMapper">
  <select id="selectBlog" resultType="Blog">
    select * from Blog where id = #{id}
  </select>
</mapper>

使用junit测试

package com.qfedu.test;

import com.qfedu.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 org.junit.Test;

import java.io.IOException;
import java.sql.Connection;
import java.util.List;

public class TestUser {

    @Test
    public void testGetAllUsers(){

        /**
         *  1.  使用mybatis的配置文件以及SqlSessionFactoryBuilder建造者模式创建SqlSessionFactory对象
         *  2.  使用SqlSessionFactory对象的openSession（）方法来得到一个SqlSession对象，用该对象即可完成对象的所有的crud操作
         *  3.  使用SqlSession对象来完成crud操作
         *  4.  关闭资源
         *
         */
        try {
            SqlSessionFactory sf = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis.xml"));

            SqlSession session = sf.openSession();

            /**
             * session的crud方法（"namespace.id"）;整个项目中的namespace.id必须唯一
             */
            List<User> users = session.selectList("com.qfedu.pojo.UserMapper.selectUser");

            for (User u : users) {
                System.out.println(u);
            }

            if(session != null){
                session.close();
                session = null;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}