第一个Mabits程序

IDEA版本:2021.2.3

jdk:11

mysql:8.0.16版本

首先先创建一个父Maven工程名为Mybatis-Study,然后将他的src文件夹删除,将他作为父工程,在其中创建子模块用于我们编写程序(方便导包,直接在父工程中使用maven来导包,而子模块中不需要一一去导入包)

父工程的pom.xml文件:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>Mybatis-Study</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>Mybatis-01</module>
    </modules>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
    </properties>
<!--    该工程为父工程,所以我删除了src文件夹-->

<!--    这里要导入三个依赖1、mysql驱动 2、mybatis 3、junit-->
    <dependencies>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.16</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>


    </dependencies>

    <!--在build中配置resources，来防止我们资源导出失败的问题-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>

</project>

然后我们在父工程中创建子模块Mybatis-01用于编写程序.

在子模块的resource文件夹中创建Mybatis的核心配置文件mybatis-config.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="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
       <mapper resource="com/kuang/dao/UserMapper.xml"/>
    </mappers>
</configuration>

创建一个实体类User,属性与mysql中你要操作的表一模一样,并设置get和set还有toString、构造方法.

package com.kuang.pojo;

public class User {
    private int id;
    private String name;
    private String pwd;

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }


    public User() {
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }

}

然后再java文件夹中创建包com.kuang.pojo中创建接口UserDao:

package com.kuang.dao;

import com.kuang.pojo.User;

import java.util.List;

public interface UserDao {
   public List<User> getUserList();//用于获取用户列表的方法
}

再继续在com.kuang.pojo包中创建xml文件实现该接口(该xml文件相当于接口的实现类):

<?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.kuang.dao.UserDao">
    <select id="getUserList" resultType="com.kuang.pojo.User">
        select * from mybatis.user
    </select>
</mapper>

要注意每一个mapper都要在mybatis的核心配置文件中注册,使用在<mappers>标签中使用<mapper>注册

然后再com.kuang.utils包下创建一个Mybatis的工具类,名为MybatisUtils,编写该类的方法,用于获取SqlSession对象.

package com.kuang.utils;

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;

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static{
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        }catch(IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSession getSqlSession(){//用于获取SqlSession对象
        return sqlSessionFactory.openSession();
    }
}

然后在test文件中编写一个测试类测试是否能够成功(快捷键ctrl+shift+t):

package com.kuang.dao;

import com.kuang.pojo.User;
import com.kuang.utils.MybatisUtils;
import junit.framework.TestCase;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest extends TestCase {
    @Test
    public void testGetUserList() {
        //1、获得了SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao userDao = sqlSession.getMapper(UserDao.class);//使用class属性来获取类的class对象
        List<User> userList = userDao.getUserList();//执行语句
        for(User user :userList){ //循环输出语句
            System.out.println(user);
        }
        sqlSession.close();//关闭sqlSession流
    }
}