利用MyBatis实现查询所有数据_mybatis查询全部数据

这操作真心记不住。。。。。还是写一遍加深记忆

1.首先创建user表，添加数据.

create datebase fuck;
 
use fuck;
 
// 删除tb_brand表
drop table if exists tb_brand;
// 创建tb_brand表
create table tb_brand
(
    -- id 主键
    id           int primary key auto_increment,
    -- 品牌名称
    brand_name   varchar(20),
    -- 企业名称
    company_name varchar(20),
    -- 排序字段
    ordered      int,
    -- 描述信息
    description  varchar(100),
    -- 状态：0：禁用  1：启用
    status       int
);
// 添加数据
insert into tb_brand (brand_name, company_name, ordered, description, status)
values ('三只松鼠', '三只松鼠股份有限公司', 5, '好吃不上火', 0),
       ('华为', '华为技术有限公司', 100, '华为致力于把数字世界带入每个人、每个家庭、每个组织，构建万物互联的智能世界', 1),
       ('小米', '小米科技有限公司', 50, 'are you ok', 1);

2.创建Maven模块，导入坐标

导入坐标

 <dependencies>
            <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
             <!--mybatis的依赖-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>
            <!--junit单元测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
 
            <!-- 添加slf4j日志api -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.20</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的核心配置文件，并且导入logback.xml文件

（1）mybatis配置文件

并且把相应的数据库信息导入进去

<?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>
 
    <!--起别名-->
    <typeAliases>
        <package name="com.fuck.pojo"/>
    </typeAliases>
 
    <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:///fuck?useSSL=false&amp;useServerPrepStmts=true"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!--扫描mapper-->
        <package name="com.fuck.mapper"/>
    </mappers>
</configuration>

（2） logback.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <!--
        CONSOLE ：表示当前的日志信息是可以输出到控制台的。
    -->
    <appender name="Console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>[%level] %blue(%d{HH:mm:ss.SSS}) %cyan([%thread]) %boldGreen(%logger{15}) - %msg %n</pattern>
        </encoder>
    </appender>
 
    <logger name="com.fuck" level="DEBUG" additivity="false">
        <appender-ref ref="Console"/>
    </logger>
 
 
    <!--
      level:用来设置打印级别，大小写无关：TRACE, DEBUG, INFO, WARN, ERROR, ALL 和 OFF
     ， 默认debug
      <root>可以包含零个或多个<appender-ref>元素，标识这个输出位置将会被本日志级别控制。
      -->
    <root level="DEBUG">
        <appender-ref ref="Console"/>
    </root>
</configuration>

4.编写pojo实体类,用get 、set方法

package com.fuck.pojo;
 
public class Brand {
       private Integer id;
        private String brandName;
        private String companyName;
        private Integer ordered;
        private String description;
        private Integer status;
 
        public Integer getId() {
            return id;
        }
 
        public void setId(Integer id) {
            this.id = id;
        }
 
        public String getBrandName() {
            return brandName;
        }
 
        public void setBrandName(String brandName) {
            this.brandName = brandName;
        }
 
        public String getCompanyName() {
            return companyName;
        }
 
        public void setCompanyName(String companyName) {
            this.companyName = companyName;
        }
 
        public Integer getOrdered() {
            return ordered;
        }
 
        public void setOrdered(Integer ordered) {
            this.ordered = ordered;
        }
 
        public String getDescription() {
            return description;
        }
 
        public void setDescription(String description) {
            this.description = description;
        }
 
        public Integer getStatus() {
            return status;
        }
 
        public void setStatus(Integer status) {
            this.status = status;
        }
 
        @Override
        public String toString() {
            return "Brand{" +
                    "id=" + id +
                    ", brandName='" + brandName + '\'' +
                    ", companyName='" + companyName + '\'' +
                    ", ordered=" + ordered +
                    ", description='" + description + '\'' +
                    ", status=" + status +
                    '}';
        }
}

5.创建mapper接口

package com.fuck.mapper;
import com.fuck.pojo.Brand;
import java.util.List;
public interface BrandMapper {
    //查询所有
    public List<Brand> selectAll();
}

6.创建SqlSessionFactory工具类

package com.fuck.Utils;
 
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
public class SqLSessionFactoryUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }
    public static SqlSessionFactory getSqlSessionFactory(){
        return sqlSessionFactory;
    }
}

总的项目结构

7.创建Mapper映射文件，并写入sql查询语句

BrandMapper.xml文件

<?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">
 
<!--namespace名称空间-->
<mapper namespace="com.fuck.mapper.BrandMapper">
<!--resultMap:
1.定义resultMap标签
2.在<select>标签中,使用resultMap属性替换resultType属性
-->
    <resultMap id="brandResultMap" type="brand">
<!--        id:完成主键字段映射-->
        <result column="brand_name" property="brandName"></result>
        <result column="company_name" property="companyName"></result>
    </resultMap>
   <!--查询所有-->
    <select id="selectAll" resultMap="brandResultMap">
select * from tb_brand;
    </select>
</mapper>

8. 最后编写测试类

MyBatisTest

package com.fuck.test;
 
import com.fuck.Utils.SqLSessionFactoryUtils;
import com.fuck.mapper.BrandMapper;
import com.fuck.pojo.Brand;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.junit.Test;
 
import java.util.Base64;
import java.util.List;
 
public class MyBatisTest {
//      调用SqlSessionFactory方法 构建出SqlSessionFactory的实例 factory
SqlSessionFactory factory= SqLSessionFactoryUtils.getSqlSessionFactory();
//   利用注解
    @Test
    public void testSelectAll(){
//        获取SqlSession
        SqlSession sqlSession= factory.openSession();
//        获取BrandMapper
        BrandMapper brandmapper=sqlSession.getMapper(BrandMapper.class);
//        调用方法
        List<Brand> brands=brandmapper.selectAll();
//         输出
        System.out.println(brands);
//         关闭sqlSession
        sqlSession.close();
        
    }
}

 运行结果