Mybatis-Plus

https://baomidou.com/

# 快速开始

添加依赖：

<!-- MySQL连接驱动 -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.19</version>
</dependency>

<!-- mp依赖 -->
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.2</version>
</dependency>

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配置文件添加数据源：

spring:
  datasource:
    username: root
    password: 123456
    url: jdbc:mysql://127.0.0.1:3306/link?characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&transformedBitIsBoolean=true&serverTimezone=GMT%2B8
    driver-class-name: com.mysql.cj.jdbc.Driver
    hikari:
      connection-test-query: select 1
      connection-timeout: 20000
      idle-timeout: 300000
      maximum-pool-size: 5
      minimum-idle: 5

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启动类添加配置扫描：

@SpringBootApplication
@MapperScan("com.Nreal.shortlink.admin.dao.mapper")
public class ShortLinkAdminApplication {
    public static void main(String[] args) {
        SpringApplication.run(ShortLinkAdminApplication.class,args);
    }
}

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# 逆向工程

https://jully.top/generator/

实体类：

@Data
@TableName("t_user")
public class UserDO extends BaseDO {

    @TableId(type = IdType.AUTO)
    private Long id;
    private String username;
    private String password;
    private String realName;
    private String phone;
    private String mail;
    private Long deletionTime;

}

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创建对应Mapper接口：

public interface UserMapper extends BaseMapper<UserDO> {
}

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创建Service接口及实现类：

public interface UserService extends IService<UserDO> {
}

@Service
@RequiredArgsConstructor
public class UserServiceImpl extends ServiceImpl<UserMapper, UserDO> implements UserService {
}

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# 条件构造器

https://baomidou.com/pages/10c804/#abstractwrapper

案例：

@Override
public UserRespDTO getUserByUsername(String username) {
    LambdaQueryWrapper<UserDO> queryWrapper = Wrappers.lambdaQuery(UserDO.class)
            .eq(UserDO::getUsername, username);
    UserDO userDO = baseMapper.selectOne(queryWrapper);
    
    //...
}

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# CRUD接口

https://baomidou.com/pages/49cc81/#service-crud-%E6%8E%A5%E5%8F%A3

# 分页查询

配置分页查询拦截器

@Configuration
public class DataBaseConfiguration {
    /**
     * 分页插件
     */
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
}

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分页查询

@Override
public IPage<ShortLinkPageRespDTO> pageShortLink(ShortLinkPageReqDTO requestParam) {
    LambdaQueryWrapper<ShortLinkDO> queryWrapper = Wrappers.lambdaQuery(ShortLinkDO.class)
            .eq(ShortLinkDO::getGid, requestParam.getGid())
            .eq(ShortLinkDO::getEnableStatus, 0)
            .eq(ShortLinkDO::getDelFlag, 0);
    IPage<ShortLinkDO> resultPage = baseMapper.selectPage(requestParam,queryWrapper);
    return resultPage.convert(each->BeanUtil.toBean(each,ShortLinkPageRespDTO.class));
}

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其它写法：

@Override
public ResponseResult hotArticleList() {
    LambdaQueryWrapper<Article> queryWrapper = new LambdaQueryWrapper<>();
    queryWrapper.eq(Article::getStatus, SystemConstants.ARTICLE_STATUS_NORMAL)
            .orderByDesc(Article::getViewCount);
    Page<Article> page = new Page(1, 10);
    page(page,queryWrapper);
    List<Article> articles = page.getRecords();
    List<HotArticleVo> hotArticleVos = BeanCopyUtils.copyBeanList(articles, HotArticleVo.class);
    return ResponseResult.okResult(hotArticleVos);
}

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@Test
public void testPage(){
    IPage<User> page = new Page<>();
    //设置每页条数
    page.setSize(2);
    //设置查询第几页
    page.setCurrent(1);
    userMapper.selectPage(page, null);
    System.out.println(page.getRecords());//获取当前页的数据
    System.out.println(page.getTotal());//获取总记录数
    System.out.println(page.getCurrent());//当前页码
}

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Mybatis→