简单的Mybatis项目

1.配置Maven依赖

依赖

<dependencies>
        <!-- mysql数据库驱动依赖  1 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.19</version>
        </dependency>
        <!-- mybatis驱动 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!--   JUnit是用于测试单元   -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.1</version>
            <scope>test</scope>
        </dependency>
        
    </dependencies>

 

2.配置环境文件mybatis-config.xml

 注意：　　　每一个Mapper.XML都需要在核心配置里面注册 

<?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.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?serverTimezone=GMT%2B8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456789"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/zxy/dao/UserMapper.xml"/>
    </mappers>
</configuration>

mapper不同配置方法（可以留印象）：

下面两种方式注意：  1.接口和Mapper配置文件同名 2.接口和Mapper配置文件在同一个包下
        <package name="com.zxy.dao"/>          
        <mapper class="com.zxy.dao.UserMapper"/>

 

 

3.编写MybatisUtils工具类

package com.zxy.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;

//sqlSessionFactory  ----> sqlSession
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            //1.获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    //SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

 

4.编写实体类User

记得数据库和实体类一一对应

package com.zxy.pojo;

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

    public User() {
    }

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

    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 getPassword() {
        return pwd;
    }

    public void setPassword(String password) {
        this.pwd = password;
    }

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

 

 

5.实体类UseDaor的接口（初学者适应  最好写成UserMapper）

package com.zxy.dao;

import com.zxy.pojo.User;

import java.util.List;

public interface UserDao {
    List<User> getUserList();
}

 

6.编写基于 XML的对于sql的映射语句UserMapper.xml

　1、namespace绑定一个对应的Dao/Mapper接口 
　2，这个XML的文件一般写在Dao目录下在pom.xml中配置文件过滤规则 Xml资源文件无法导出，找不到Mapper.xml文件
　　　　　　　　　　　　　　　　　　　　　　　　点此连接可以得到配置代码

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

 

7.编写测试类

public class UserDaoTest {
        @Test
        public void test(){
            //1.获取sqlSession对象
            SqlSession sqlSession = MybatisUtils.getSqlSession();
            //2.
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            List<User> userList = userDao.getUserList();

            for ( User user :userList) {
                System.out.println(user);
            }
            //关闭SqlSession
            sqlSession.close();
        }
}