具体的数据库操作

Brand类

package com.itheima.pojo;

/**
 * 品牌
 *
 * alt + 鼠标左键：整列编辑
 *
 * 在实体类中，基本数据类型建议使用其对应的包装类型
 */

public class Brand {
    // id 主键
    private Integer id;
    // 品牌名称
    private String brandName;
    // 企业名称
    private String companyName;
    // 排序字段
    private Integer ordered;
    // 描述信息
    private String description;
    // 状态：0：禁用  1：启用
    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 +
                '}';
    }
}

BrandMapper文件：一个接口用于执行

package com.itheima.mapper;


import com.itheima.pojo.Brand;
import org.apache.ibatis.annotations.Param;

import java.util.List;
import java.util.Map;

public interface BrandMapper {


    public List<Brand> selectAll();

    /*
    * 查看详情
    * */
    Brand selectById(int id);

    /*
    * 完成的是条件查询
    *   *参数接收
    *       1.散装参数：如果方法中有多个参数，需要使用@Param("SQL参数占位符名称")
    *       2.对象参数：对象的属性名称要和参数占位符名称一致
    *       3.map集合参数
    * */
    //List<Brand> selectByCondition(@Param("status") int status, @Param("companyName") String companyName,@Param("brandName") String brandName);





    //List<Brand> selectByCondition(Brand brand);

    List<Brand> selectByCondition(Map map);



}

对应的BrandMapper.xml文件，用于写具体的sql语句

<?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.itheima.mapper.BrandMapper">


    <resultMap id="brandResultMap" type="brand">
        <result column="brand_name" property="brandName"></result>
        <result column="company_name" property="companyName"></result>
    </resultMap>




    <select id="selectAll" resultMap="brandResultMap">
        select *
        from tb_brand ;

    </select>

    <!--
        数据库的字段名称   和 实体类的属性名称不一样  ， 则不能自动封装数据
        *起别名:对不一样的列名起别名 让别名和实体类名字相同
            *缺点 每次查询都要定义一次别名

        *sql片段

        *resultMap
    -->

    <!--<select id="selectAll" resultType="brand">
        select * from tb_brand ;
    </select>-->

   <!-- <select id="selectAll" resultType="brand">
        select id, brand_name as brandName, company_name as companyName, ordered, description, status
        from tb_brand ;

    </select>
-->


    <!--
       *参数占位符：
         1.#{}:会将其替换为?,为了防止sql注入
         2.${}:拼sql。会存在sql注入问题
         3.使用时机：
               * 参数传递的时候：#{}
               * 表名或者列名不固定的情况下：${}

       *参数类型：parameterType 可以省略
       *特殊字符的处理：
           1.转义字符：
           2.CDATA区:
   -->
    <select id="selectById" resultMap="brandResultMap">
        select *
        from tb_brand where id = #{id};

    </select>


    <!--
    条件查询
    -->
    <!--<select id="selectByCondition" resultMap="brandResultMap">
        select *
        from tb_brand
        where
            status = #{status}
        and company_name like #{companyName}
        and brand_name like #{brandName}
    </select>-->

    <!--
        动态条件查询
            *if:条件判断
               * test:逻辑表达式
            *问题:
                *恒等式 加入条件 where 1 = 1 并在每个if逻辑表达式里面加上and
                *<where>标签 替换where关键字


    -->
    <select id="selectByCondition" resultMap="brandResultMap">
        select *
        from tb_brand
        <where>

          <if test="status != null">
            and  status = #{status}
          </if>

          <if test="companyName != null and companyName != ''">
            and company_name like #{companyName}
          </if>

          <if test="brandName != null and brandName != ''">
            and brand_name like #{brandName}
          </if>
        </where>
    </select>


</mapper>

执行具体的主要java test示例

MybatisTest.java

package com.itheima.test;

import com.itheima.mapper.BrandMapper;
import com.itheima.pojo.Brand;
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.HashMap;
import java.util.List;
import java.util.Map;

public class MybatisTest {

    @Test
    public void testSelectAll() throws IOException {
        //1.获取SqlSessionFactory
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2.获取SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();


        //3.获取Mapper接口的代理对象
        BrandMapper brandMapper  =sqlSession.getMapper(BrandMapper.class);

        //4.执行方法
        List<Brand> brands = brandMapper.selectAll();


        System.out.println(brands);

        //5.释放资源
        sqlSession.close();
    }


    @Test
    public void testSelectById() throws IOException {
        int id = 1;
        //1.获取SqlSessionFactory
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2.获取SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();


        //3.获取Mapper接口的代理对象
        BrandMapper brandMapper  =sqlSession.getMapper(BrandMapper.class);

        //4.执行方法
        Brand brand = brandMapper.selectById(id);


        System.out.println(brand);

        //5.释放资源
        sqlSession.close();
    }

    @Test
    public void testSelectByCondition() throws IOException {
        //接收参数
        int status = 1;
        String companyName = "华为";
        String brandName = "华为";

        //处理
        companyName = "%"+ companyName + "%";
        brandName = "%"+ brandName + "%";

       /* //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
        brand.setCompanyName(companyName);
        brand.setBrandName(brandName);*/

        Map map = new HashMap();
        //map.put("status",status);
        map.put("companyName",companyName);
        //map.put("brandName",brandName);

        //1.获取SqlSessionFactory
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2.获取SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();


        //3.获取Mapper接口的代理对象
        BrandMapper brandMapper  =sqlSession.getMapper(BrandMapper.class);

        //4.执行方法

        //List<Brand> brands = brandMapper.selectByCondition(status,companyName,brandName);
        //List<Brand> brands = brandMapper.selectByCondition(brand);
        List<Brand> brands = brandMapper.selectByCondition(map);


        System.out.println(brands);

        //5.释放资源
        sqlSession.close();
    }


}