springboot+mybatis两表查询，以及+plus增删改

朴灿烈づ我的快乐病毒、 2023-09-27 13:24 73阅读 0赞

### 一、添加依赖如下(springboot我使用的统一版本是2.7.6)： ###

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.7.6</version>
            <relativePath/> 
        </parent>
        <groupId>com.boot.mybatisplus</groupId>
        <artifactId>springboot_plus</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>springboot_plus</name>
        <description>Demo project for Spring Boot</description>
        <properties>
            <java.version>1.8</java.version>
        </properties>
        <dependencies>
            <dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
                <version>3.4.1</version>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>2.3.0</version>
            </dependency>
    
            <dependency>
                <groupId>com.mysql</groupId>
                <artifactId>mysql-connector-j</artifactId>
                <scope>runtime</scope>
            </dependency>
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <optional>true</optional>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                    <configuration>
                        <excludes>
                            <exclude>
                                <groupId>org.projectlombok</groupId>
                                <artifactId>lombok</artifactId>
                            </exclude>
                        </excludes>
                    </configuration>
                </plugin>
            </plugins>
        </build>
    
    </project>

### 二、配置数据源 ###

>     #配置数据源
>     spring:
>       datasource:
>         url: jdbc:mysql://127.0.0.1:3306/petptype?serverTimezone=UTC
>         username: root
>         password: root
>         driver-class-name: com.mysql.cj.jdbc.Driver
>     
>     # 配置mybatis规则
>     mybatis:
>       #  config-location: classpath:mybatis/mybatis-config.xml
>       mapper-locations: classpath:mapper/*.xml
>       configuration: #指定mybatis全局配置文件中的相关配置项
>         map-underscore-to-camel-case: true
>         log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
>       type-aliases-package: com.boot.mybatisplus.pojo

### 三、因为我们要进行两表联查，我会展示两种方式进行两表联查（第一种就是以下的在Goods实体类中引用Type实体类）   ![8b99b3cd28a34e5393ffcb16cd9b60e3.png][] ###

## 使用resultMap标签 ##

<resultMap id="goodsAndType" type="com.boot.mybatis.pojo.Goods">
            <id property="id" column="eid"></id>
            <result property="id" column="id"></result>
            <result property="goodsName" column="goods_name"></result>
            <result property="goodsPrice" column="goods_price"></result>
            <result property="goodsNum" column="goods_num"></result>
            <result property="goodsType" column="goods_type"></result>
            <result property="remark" column="remark"></result>
            
            <association property="type" javaType="com.boot.mybatis.pojo.Type">
                <id property="typeId" column="typeId"></id>
                <result property="typeName" column="typeName"></result>
            </association>
        </resultMap>
        <select id="findGoodsAndType" resultMap="goodsAndType">
            select * from goods g,type t where g.goods_type=t.typeId
        </select>

### 两表联查的第二种方式就是直接在Goods实体类中添加一个查询字段，利用@TableField来标识该属性不为数据库表的字段   ![e35401cba4e248798d7646667a3df69f.png][] ###

### 四、mapper层（持久层）我们直接继承BaseMapper<Goods>   ![09568462c259442da1783425916cd084.png][] ###

### 五、service层（业务逻辑层）我们继承IService<Goods>，impl继承ServiceImpl<GoodsMapper, Goods>以及实现service接口 ###

### 六、controller（控制逻辑层）   ![288205f4fa164f63b36b64d63b97035b.png][] ###

[8b99b3cd28a34e5393ffcb16cd9b60e3.png]: https://img-blog.csdnimg.cn/8b99b3cd28a34e5393ffcb16cd9b60e3.png
[e35401cba4e248798d7646667a3df69f.png]: https://img-blog.csdnimg.cn/e35401cba4e248798d7646667a3df69f.png
[09568462c259442da1783425916cd084.png]: https://img-blog.csdnimg.cn/09568462c259442da1783425916cd084.png
[288205f4fa164f63b36b64d63b97035b.png]: https://img-blog.csdnimg.cn/288205f4fa164f63b36b64d63b97035b.png