SpringBoot教学补充资料2-MyBatis简单查询项目

SQL：

CREATE TABLE `tb_user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(20) DEFAULT NULL,
  `password` varchar(20) DEFAULT NULL,
  `gender` char(1) DEFAULT NULL,
  `addr` varchar(30) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8

INSERT INTO tb_user VALUES (1,'zhangsan','123','男','北京');
INSERT INTO tb_user VALUES (2,'李四','111','女','上海');
INSERT INTO tb_user VALUES (3,'王五','122','男','河北');

创建Maven项目：

 项目结构：

pom.xml:

<dependencies>
    <!--        mybatis的依赖-->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.2</version>
    </dependency>

    <!--        mysql驱动-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.28</version>
    </dependency>

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

</dependencies>

java下创建pojo包，pojo包下创建User.java:

public class User {
    private Integer id;
    private String username;
    private String password;
    private String gender;
    private String addr;
//getter&setter
    public Integer getId() {
        return id;
    }

    public void setId(Integer 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;
    }
//    toString

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

resource下新建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">
<!--                数据库连接信息-->
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///mybatis?useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
<!--    加载SQL映射文件路径-->
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

新建mapper包，包下新建UserMapper接口。

import pojo.User;

import java.util.List;

public interface UserMapper {
    List<User> selectAll();
}

resource下新建UserMapper.xml映射.

<?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">
<mapper namespace="testmapper">  <!--名称空间-->
    <select id="selectAll" resultType="pojo.User"><!--id:唯一标识   resultType：返回结果的类型-->
        select * from tb_user;
    </select>
</mapper>

java下创建测试类test.java：

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 pojo.User;

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

public class test {
    public static void main(String[] args) throws IOException {
//1.加载mybatis的核心配置文件，获取sqlSessionFactory
        String resource = "mybatis-config.xml";//定义配置文件路径
        InputStream inputStream = Resources.getResourceAsStream(resource);//输入流进行资源加载，传入字符串返回输入流
        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,自动封装结果集
        List<User> users = sqlSession.selectList("testmapper.selectAll");
        System.out.println(users);
//4.释放资源
        sqlSession.close();

    }
}

在test.java类中启动运行：

 运行成功！