Mybatis（1.環境搭建）

先給出項目目錄結構：

1.IDEA創建Maven工程，不選擇框架。

2. pom.xml文件中導入依賴

<dependencies>
        <!-- mybatis依賴 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <!-- mysql數據庫連接依賴 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.20</version>
        </dependency>
        <!-- 日志依賴 -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <!-- 測試依賴 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

3.建立實體類User以及對應dao接口IUserDao（以下面為例）

4.為剛創建的dao接口創建對應的映射配置文件IUserDAO.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- mybatis映射配置文件的約束-->
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">


<mapper namespace="com.dfan.dao.IUserDao">

    <select id="findAll" resultType="com.dfan.domain.User">
        select * from user
    </select>
</mapper>

5.創建Mybatis主配置文件SqlMapCongfig.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- mybatis主配置文件的約束 -->
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<!-- mybatis的主配置文件 -->
<configuration>
    <!-- 配置環境 -->
    <environments default="mysql">
        <!-- 配置mysql的環境 -->
        <environment id="mysql">
            <!-- 配置事務的類型 -->
            <transactionManager type="JDBC"/>
            <!-- 配置數據源（連接池） -->
            <dataSource type="POOLED">
                <!-- 配置連接數據庫的4個基本信息 -->
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <!-- 加上serverTimezone=UTC為了解決mysql8.0時區問題 -->
                <property name="url" value="jdbc:mysql://localhost:3306/eesy?serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="121509"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 配置xxxmapper.xml（或xxxdao.xml）配置文件 -->
    <mappers>
        <mapper resource="com/itheima/dao/IUserDao.xml"/>
    </mappers>
</configuration>

6.編寫測試類MybatisTest進行測試

package com.dfan.test;

import com.dfan.dao.IUserDao;
import com.dfan.domain.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 java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * @Author: dfan
 * @Date: 2020/8/24
 */
public class MybatisTest {

    public static void main(String[] args) throws IOException {
        //1.讀取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.創建SqlSessionFactory工廠
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        //3.使用工廠生產SqlSession對象
        SqlSession session = factory.openSession();
        //4.使用SqlSession創建Dao接口的代理對象
        IUserDao dao = session.getMapper(IUserDao.class);
        //5.使用代理對象執行方法
        List<User> users = dao.findAll();
        for (User user : users) {
            System.out.println(user);
        }
        //6.釋放資源
        session.close();
        in.close();
    }
}

7.運行結果