mybatis(一)安裝

1.創建web項目,添加jar包

2.創建實驗表user_t

3.在src下創建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" />
            <!-- 配置數據庫連接信息 -->
            <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、定義表所對應的實體類，

package com.mi.entity;

public class User {

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

...

}

3、定義操作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文件中注冊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" />
            <!-- 配置數據庫連接信息 -->
            <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"/><!-- 注冊userMapper.xml文件， -->
    </mappers>
</configuration>

5、編寫測試代碼：執行定義的select語句

　　創建一個Test1類，編寫如下的測試代碼：

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";
         //使用類加載器加載mybatis的配置文件（它也加載關聯的映射文件）
        InputStream is = Test1.class.getClassLoader().getResourceAsStream(resource);
         //構建sqlSession的工廠
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
        //使用MyBatis提供的Resources類加載mybatis的配置文件（它也加載關聯的映射文件）
        //Reader reader = Resources.getResourceAsReader(resource); 
        //構建sqlSession的工廠
        //SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        //創建能執行映射文件中sql的sqlSession
        SqlSession session = sessionFactory.openSession();
        /**
         * 映射sql的標識字符串，
         * com.mi.mapping.UserInfoMapper是UserInfoMapper.xml文件中mapper標簽的namespace屬性的值，
         * queryUserInfo是select標簽的id屬性值，通過select標簽的id屬性值就可以找到要執行的SQL
         */
        String statement = "com.mi.mapping.UserInfoMapper.queryUserInfo";//映射sql的標識字符串
        User user = session.selectOne(statement,1);//執行查詢返回一個唯一user對象的sql
        System.out.println(user.getId());
        System.out.println(user.getUserName());
        System.out.println(user.getAge());
    }
}

結果如下: