从零开始Mybatis连接数据库

创建Maven文件

File-->new-->project-->maven,点击next

在出现的pom.xml文件中<project>标签之间加入以下内容

 <!--打包方式-->
<packaging>jar</packaging>

    <dependencies>
        <!--加载Mybatis核心-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>

        <!--Junit测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

        <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.3</version>
        </dependency>

    </dependencies>

在src-->main-->resources下创建文件mybatis-config.xml

在该文件中加入以下内容:

<?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>
    <!--配置连接数据库环境-->
    <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/test"/>
                <property name="username" value="自己的用户名"/>
                <property name="password" value="自己的密码"/>
            </dataSource>
        </environment>
    </environments>

</configuration>

注意将username和password的value值改成自己的,且在自己的数据库中创建test库

创建实体类

在main的java下创建我们需要与表中对应的实体类,这里我们写user类

public class User {
    //实体类
    
    //属性与表中的各项对应,加入相应的get,set方法
        int  userid;
        String username;
        String userpass;
        String usertel;
        int usercarad;

        public User() {
        }

        public User(int userid, String username, String userpass, String usertel, int usercarad) {
            this.userid = userid;
            this.username = username;
            this.userpass = userpass;
            this.usertel = usertel;
            this.usercarad = usercarad;
        }

        public int getUserid() {
            return userid;
        }

        public void setUserid(int userid) {
            this.userid = userid;
        }

        public String getUsername() {
            return username;
        }

        public void setUsername(String username) {
            this.username = username;
        }

        public String getUserpass() {
            return userpass;
        }

        public void setUserpass(String userpass) {
            this.userpass = userpass;
        }

        public String getUsertel() {
            return usertel;
        }

        public void setUsertel(String usertel) {
            this.usertel = usertel;
        }

        public int getUsercarad() {
            return usercarad;
        }

        public void setUsercarad(int usercarad) {
            this.usercarad = usercarad;
        }
    }

    

创建com.mapper包,并在包下创建UserMapper接口

这里我们简单做一个添加内容示例

package com.mapper;

public interface UserMapper {
    int insertUser();//返回值为改变的行数
}

创建UserMapper.xml映射文件

在resources文件夹下创建mapper文件夹(包)并在其中创建UserMapper.xml

并在其中加入以下内容,这里要保证两个一致

<?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">
<!--第一个一致,namespace对应UserMapper接口全类名-->
<mapper namespace="com.mapper.UserMapper">

    <!--第二个一致,id对应方法名   int  insertUser(); -->
   <insert id="insertUser">
       insert into user values (null,"tom","1234","111",22)
   </insert>

</mapper>

在mybatis-config.xml下<configuration>标签中最下面加入

<!--引入映射文件-->
    <mappers>
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>

创建测试类

创建Test类进行测试

import com.mapper.UserMapper;
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.Reader;

public class Test {
    public static void main(String[] args) throws IOException {
        //获取配置文件
       Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
       // 获取SqlSessionFactoryBuilder获取SqlSessionFactory工厂
       SqlSessionFactoryBuilder sqlSessionFactoryBuilder=new SqlSessionFactoryBuilder();
        //获取SqlSessionFactory工厂
        SqlSessionFactory sqlSessionFactory= sqlSessionFactoryBuilder.build(reader);
        //利用工厂获取sqlSession
        SqlSession sqlSession=sqlSessionFactory.openSession();//openSession()加入参数true,即可实现自动提交事务
        //利用sqlSession的方法获取接口的对象
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        //调用接口方法,从而调用映射文件的sql语句
       int num= userMapper.insertUser();
       //提交事务
        sqlSession.commit();
        System.out.println("改变行数"+num);


    }
}

运行结果: