mybatis(一)安装

1.创建web项目,添加jar包

2.创建实验表user_t

3.在src下创建conf.xml文件,如下

<?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" />
            <!-- 配置数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost/mi" />
                <property name="username" value="root" />
                <property name="password" value="dbdaocom" />
            </dataSource>
        </environment>
    </environments>
    
</configuration>

2、定义表所对应的实体类，

package com.mi.entity;

public class User {

    private int id;
    private String userName;
    private String password;
    private Integer age;

...

}

3、定义操作users表的sql映射文件userMapper.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">
<mapper namespace="com.mi.dao.UserInfoMapper">
    
     <select id="queryUserInfo" resultType="com.mi.entity.User">
        SELECT id,user_name userName,age FROM user_t where 1=1
    </select>
    <select id="getCount" resultType="int">
        SELECT count(*) FROM user_t
    </select>
    
</mapper>

4、在conf.xml文件中注册userMapper.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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <!-- 配置数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost/mi" />
                <property name="username" value="root" />
                <property name="password" value="dbdaocom" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/mi/mapping/UserInfoMapper.xml"/><!-- 注册userMapper.xml文件， -->
    </mappers>
</configuration>

5、编写测试代码：执行定义的select语句

　　创建一个Test1类，编写如下的测试代码：

package com.mi.demo;

import java.io.InputStream;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.mi.entity.User;

public class Test1 {

    public static void main(String[] args) {
        //mybatis的配置文件
        String resource = "conf.xml";
         //使用类加载器加载mybatis的配置文件（它也加载关联的映射文件）
        InputStream is = Test1.class.getClassLoader().getResourceAsStream(resource);
         //构建sqlSession的工厂
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
        //使用MyBatis提供的Resources类加载mybatis的配置文件（它也加载关联的映射文件）
        //Reader reader = Resources.getResourceAsReader(resource); 
        //构建sqlSession的工厂
        //SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        //创建能执行映射文件中sql的sqlSession
        SqlSession session = sessionFactory.openSession();
        /**
         * 映射sql的标识字符串，
         * com.mi.mapping.UserInfoMapper是UserInfoMapper.xml文件中mapper标签的namespace属性的值，
         * queryUserInfo是select标签的id属性值，通过select标签的id属性值就可以找到要执行的SQL
         */
        String statement = "com.mi.mapping.UserInfoMapper.queryUserInfo";//映射sql的标识字符串
        User user = session.selectOne(statement,1);//执行查询返回一个唯一user对象的sql
        System.out.println(user.getId());
        System.out.println(user.getUserName());
        System.out.println(user.getAge());
    }
}

结果如下: