Mybatis 的快速入门

Mybatis 的快速入门

• 1.创建tb_user表，添加几条数据

• 2.创建模块，导入坐标（使用pom.xml配置mybatis）

	<dependencies>
        <!--mybatis 的依赖-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>

        <!--连接数据库， 导入mysql的驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.44</version>
        </dependency>

        <!--用到测试类，导入junit 单元测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
        </dependency>

        <!-- 添加slf4j日志api -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.26</version>
        </dependency>
        <!-- 添加logback-classic依赖 -->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>
        <!-- 添加logback-core依赖 -->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>1.2.3</version>
        </dependency>
    </dependencies>

• 3.编写Mybatis 核心配置文件，替换连接，解决编码问题，一般名称命名为：mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!--连接数据库的信息-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <!--防止出现中文查询不出来，设置useUnicode=true&amp;characterEncoding=UTF-8-->
                <property name="url" value="jdbc:mysql:///mybatis?useSSL=false&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <!--方法1：加载sql的映射路径  单个添加-->
    <mappers>
        <mapper resource="UserMapper.xml"/>
        <mapper resource="com/yz/Mapper/BrandMapper.xml"/>
    </mappers>

    <!--
    <方法2：扫描mapper的包下面的xml文件 扫描全部
    <mappers>
        <package name="com.itheima.mapper"/>
    </mappers>
    -->
</configuration>

• 编写对应的UserMapper.xml文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">

<!--namespace是名称空间-->
<mapper namespace="test">
    <!--resultType 是返回结果得类型-->
    <select id="selectAll" resultType="com.yz.pojo.User">
        select * from tb_user ;
    </select>
</mapper>

• 加载对应的UserMapper.xml文件

	<mappers>
        <mapper resource="UserMapper.xml"/>
        <mapper resource="com/yz/Mapper/BrandMapper.xml"/>
    </mappers>

• 4.进入到编码，定义一个实体类user

package com.yz.pojo;

public class User {
    
    

    private int id;
    private String username;
    private String password;
    private String gender;
    private String addr;

    public int getId() {
    
    
        return id;
    }

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

    public String getUsername() {
    
    
        return username;
    }

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

    public String getPassword() {
    
    
        return password;
    }

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

    public String getGender() {
    
    
        return gender;
    }

    public void setGender(String gender) {
    
    
        this.gender = gender;
    }

    public String getAddr() {
    
    
        return addr;
    }

    public void setAddr(String addr) {
    
    
        this.addr = addr;
    }

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

• 5.测试类

import com.yz.pojo.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 org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisDemo {
    
    

    @Test
    public void testSelectAll() throws IOException {
    
    
        //1.加载mybatis的核心配置文件，获取SQLSessionFactary

        //定义配置文件路径
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2.获取SqlSession对象，用它来执行SQL
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //3.执行SQL语句
        List<User> users = sqlSession.selectList("test.selectAll");

        System.out.println(users);

        //4.释放资源
        sqlSession.close();



    }
}