MyBatis实现对数据库的增删改查

首先，整个项目的结构如图：

本次主要是对tb_brand表实现增删改查。

创建先后顺序

创建的先后顺序我在前一篇博客已经说清楚了，就不再赘述了，如果不知道如何创建的话，说明对mybatis还是不了解，建立仔细看一看上一篇博客，这是链接：一篇博客带你学会MyBatis

Brand实体类

package com.itheima.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;
    }

    @Override
    public String toString() {
        return "Brand{" +
                "id=" + id +
                ", brandName='" + brandName + '\'' +
                ", companyName='" + companyName + '\'' +
                ", ordered=" + ordered +
                ", description='" + description + '\'' +
                ", status=" + status +
                '}';
    }

    public Integer getStatus() {
        return status;
    }

    public void setStatus(Integer status) {
        this.status = status;
    }

}

mapper接口

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 {

    /**
     * 查询所有
     */
    public List<Brand> selectAll();

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

    /**
     * 条件查询
     *  * 参数接收
     *      1.散装对象  如果方法中有多个参数，需使用@Param("sql占位符名称")
     *      2.封装对象
     *      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);

    /**
     * 单条件动态查询
     * @param brand
     * @return
     */
    List<Brand> selectByConditionSingle(Brand brand);

    /**
     * 添加
     */
    void add(Brand brand);

    /**
     * 修改功能
     */
    int update(Brand brand);

    /**
     * 根据id删除
     */
    void delById(int id);

    /**
     * 批量删除
     */
    void delByIds(@Param("ids") int[] ids);

}

sql映射文件

<?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.itheima.mapper.BrandMapper">

    <!--
    数据库表的字段名称 和 实体类的属性名称不一样，则不能自动封装
    *起别名：对不一样的列名起别名，让别名和实体类的属性名一样
        *缺点:每次查询都要定义一次别名
        *解决:使用sql片段（但还是不灵活）
    *resultMap：
        1. 定义<resulMap>标签
        2. 在<select>标签中使用resulMap属性替换resultType属性
     -->

    <!--
     sql片段
    -->
    <!--    <sql id="brand_cloumn">id, brand_name as brandName, company_name as companyName, ordered, description, status</sql>-->

    <!--    <select id="selectAll" resultType="brand">-->
    <!--        select-->
    <!--            <include refid="brand_cloumn"></include>-->
    <!--        from tb_brand;-->
    <!--    </select>-->

    <!-- id:唯一标识 type：映射的类型，支持别名 -->
    <resultMap id="brandResultMap" type="brand">
        <!-- id:完成主键字段的映射 result：完成一般字段的映射 -->
        <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>

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

            *参数类型 ：parameterType：可以省略

            *特殊字符的处理：
                1.转义字符
                2.CDATA区 <![CDATA[ 内容 ]]>

        -->

    <select id="selectById" resultMap="brandResultMap">
        select *
        from tb_brand where id &lt; #{id};
    </select>

    <!--    <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
            *<where> 替换 where关键字

    -->
    <select id="selectByCondition" resultMap="brandResultMap">
        select *
        from tb_brand
        /*where 1 = 1*/
        <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>
    <select id="selectByConditionSingle" resultMap="brandResultMap">
        select *
        from tb_brand
        <where>
            <choose><!-- 相当于switch -->
                <when test="status != null"><!-- 相当于case -->
                    status = #{status}
                </when>
                <when test="companyName != null and companyName != '' ">
                    company_name like #{companyName}
                </when>
                <when test="brandName != null and brandName != '' ">
                    brand_name like #{brandName}
                </when>
                <!--            <otherwise>-->
                <!--                1 = 1-->
                <!--            </otherwise>-->

            </choose>
        </where>
    </select>

    <insert id="add" useGeneratedKeys="true" keyProperty="id">
        insert into tb_brand (brand_name,company_name,ordered,description,status)
        values (#{brandName},#{companyName},#{ordered},#{description},#{status});
    </insert>

    <update id="update">
        update tb_brand
        <set>
        <if test="brandName != null and brandName != ''">
            brand_name = #{brandName},
        </if>

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

        <if test="ordered != null">
            ordered = #{ordered},
        </if>

        <if test="description != null and description != '' ">
            description = #{description},
        </if>

        <if test="status != null">
            status = #{status}
        </if>
        </set>
        where id = #{id};
    </update>

    <delete id="delById">
        delete from tb_brand where id = #{id};
    </delete>

    <!-- mybatis会将数组参数，封装成一个map集合
            *默认： array = 数组
            *使用@Param参数注解改变map集合key的名称
    -->
    <delete id="delByIds">
        delete from tb_brand where id
        in  <foreach collection="ids" item="id" separator="," open="(" close=")">
                #{id}
            </foreach>
    </delete>

</mapper>

核心配置文件

<?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>

    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING" />
    </settings>
    <!-- 别名,UserMapper.xml文件中resultType属性就可以写pojo下的类名（类名还可以不区分大小写） -->
    <typeAliases>
        <package name="com.itheima.pojo"/>
    </typeAliases>

    <!--
    environments：配置数据库链接环境信息，可以配置多个environment，通过切换default属性切换不同的environment
    -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!-- 数据库链接信息 -->
                <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>

        <environment id="test">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!-- 数据库链接信息 -->
                <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>
    <mappers>
        <!-- 加载sql映射文件 -->
        <!-- <mapper resource="com/itheima/mapper/UserMapper.xml"/>-->

        <!-- mapper代理方式 -->
        <package name="com.itheima.mapper"/>
    </mappers>
</configuration>

执行sql完成增删改查

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

        //1. 加载MyBatis配置文件，获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2. 获取SqlSession对象
        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 {

        //接收参数
        int id = 1;

        //1. 获取sqlsessionFactory

        //1. 加载MyBatis配置文件，获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2. 获取SqlSession对象
        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";

        //处理参数
        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

        //1. 加载MyBatis配置文件，获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2. 获取SqlSession对象
        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();
    }

    @Test
    public void testSelectByConditionSingle() throws IOException {

        //接收参数
        int status = 1;
        String companyName = "华为";
        String brandName = "华为";

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

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

        //1. 获取sqlsessionFactory

        //1. 加载MyBatis配置文件，获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2. 获取SqlSession对象
        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.selectByConditionSingle(brand);
        System.out.println(brands);
        //5. 释放资源
        sqlSession.close();
    }

    @Test
    public void testAdd() throws IOException {

        //接收参数
        int status = 1;
        String companyName = "波导手机2";
        String brandName = "波导2";
        String description = "手机中的战斗机";
        int ordered = 100;

        //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
        brand.setCompanyName(companyName);
        brand.setBrandName(brandName);
        brand.setDescription(description);
        brand.setOrdered(ordered);

        //1. 获取sqlsessionFactory

        //1. 加载MyBatis配置文件，获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

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

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

        //4. 执行方法
        brandmapper.add(brand);
        Integer id = brand.getId();
        System.out.println(id);

        //提交事务
        //sqlSession.commit();

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

    @Test
    public void testUpdate() throws IOException {

        //接收参数
        int status = 0;
        String companyName = "波导手机";
        String brandName = "波导";
        String description = "波导手机,手机中的战斗机";
        int ordered = 200;
        int id = 6;

        //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
        //brand.setCompanyName(companyName);
        //brand.setBrandName(brandName);
        //brand.setDescription(description);
        //brand.setOrdered(ordered);
        brand.setId(id);

        //1. 获取sqlsessionFactory

        //1. 加载MyBatis配置文件，获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2. 获取SqlSession对象
        //SqlSession sqlSession = sqlSessionFactory.openSession();
        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
        int count = brandmapper.update(brand);
        System.out.println(count);

        //提交事务
        sqlSession.commit();

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

    @Test
    public void testDelById() throws IOException {

        //接收参数
        int id = 6;

        //1. 获取sqlsessionFactory

        //1. 加载MyBatis配置文件，获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2. 获取SqlSession对象
        //SqlSession sqlSession = sqlSessionFactory.openSession();
        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
        brandmapper.delById(id);

        //提交事务
        sqlSession.commit();

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

    @Test
    public void testDelByIds() throws IOException {

        //接收参数
        int[] ids = {6,7};

        //1. 获取sqlsessionFactory

        //1. 加载MyBatis配置文件，获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2. 获取SqlSession对象
        //SqlSession sqlSession = sqlSessionFactory.openSession();
        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
        brandmapper.delByIds(ids);

        //提交事务
        sqlSession.commit();

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

}

maven配置文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>mybatis-demo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <!-- mybatis的依赖 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</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>4.13.1</version>
            <scope>test</scope>
        </dependency>

        <!-- 添加slf4j日志api -->
<!--        <dependency>-->
<!--            <groupId>org.slf4j</groupId>-->
<!--            <artifactId>slf4j-log4j12</artifactId>-->
<!--            <version>1.7.19</version>-->
<!--        </dependency>-->
    </dependencies>

</project>