Springboot 2.3.5使用 Mybatis 实现增删改查（单表），并实现增改获取对应的id

参考

1. springboot+mybatis 插入新数据并返回该数据id值
2. Mybatis XML 映射器
3. mybatis中的sql语句的返回值

知识点

1. 取出刚刚插入的id

   1. 通过给insert、update的xml映射语句设置useGeneratedKeys与keyProperty属性，可以让mybatis取出由数据库内部生成的主键，如果生成列不止一个，可以用逗号分隔多个属性名称。
   2. 需要将文章实体实例化之后作为参数传入Mapper的查询方法，这样mybatis就会按照 1 的设置将新增/修改的id传入到文章实体内，然后把文章实体返回给控制器，控制器就能够获取到刚刚插入/修改的id了。

2. 增删改查语句使用不同的标签进行处理，查询：select、新增：insert、修改：update、删除：delete。

3. 语句默认返回值 ，引用自mybatis中的sql语句的返回值

   1. select语句

      1. 正确执行时，返回查询的结果或结果集
      2. 未查询到结果，返回值为null

   2. insert语句

      1. 正确执行时，返回在数据库中影响的行数
      2. 插入数据失败，抛出com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException

   3. update语句

      1. 正确执行时,返回在数据库中匹配的行数
      2. 插入数据失败，抛出com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException

   4. delete语句

      1. 正确执行时,返回在数据库中影响的行数
      2. 插入数据失败，抛出com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException

（单表）实现增删改查代码

1. 实体

   1. 文章实体 entity/ArticleEntity.java

   		/**
   		 * 文章实体
   		 * @Author 夏秋初
   		 * @Date 2021/8/13 10:10
   		 */
   		@Data
   		@JsonNaming(PropertyNamingStrategy.SnakeCaseStrategy.class)
   		public class ArticleEntity implements Serializable {
   			/**
   			 * 序列化安全
   			 */
   			private static final long serialVersionUID = 1L;
   			private Integer id;
   			private String title;
   			private String introduction;
   			private Date createdAt;
   			private Date updatedAt;
   			private String content;
   			private Integer shows;
   			private Integer likes;
   		}
   

   2. 文章添加Dto dto/admin/request/ArticleAddDto.java

   	/**
   	 * @Author 夏秋初
   	 * @Date 2021/8/16 10:45
   	 */
   	@Data
   	public class ArticleAddDto {
   		private String title;
   		private String introduction;
   		private String content;
   	}
   

   3. 文章更新Dto dto/admin/request/ArticleUpdateDto.java

   	/**
   	 * @Author 夏秋初
   	 * @Date 2021/8/16 10:45
   	 */
   	@Data
   	public class ArticleUpdateDto {
   		private String title;
   		private String introduction;
   		private String content;
   	}
   

2. 文章xml映射文件 resources/mappers/ArticleMapper.xml

<?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">
<!--这里对应Maper接口类的命名空间-->
<mapper namespace="com.xxx.blog.mapper.ArticleMapper">
    <!--    这里 resultType 对应响应实体类，也可以是其他类型，请参考文档-->
    <select id="findById" parameterType="int" resultType="com.xxx.blog.entity.ArticleEntity">
        select * from `articles` where id = #{id}
    </select>
    <select id="findByPaging" resultType="com.xxx.blog.entity.ArticleEntity" parameterType="map">
        select
        *
        from `articles`
    </select>
    <insert id="add" useGeneratedKeys="true"
            keyProperty="id" parameterType="com.xxx.blog.entity.ArticleEntity">
        insert into articles (title, introduction,content,created_at,updated_at) values(#{title}, #{introduction},#{content},#{createdAt},#{updatedAt})
    </insert>
    <update id="update" useGeneratedKeys="true" keyProperty="id" parameterType="com.xxx.blog.entity.ArticleEntity">
        update articles set
                title = #{title}, introduction = #{introduction}, content=#{content}, updated_at = #{updatedAt}
        where id = #{id}
    </update>
    <delete id="delete" parameterType="int">
        delete from articles where id = #{id}
    </delete>
</mapper>

3. 文章Mapper类 mapper/ArticleMapper.java

/**
 * @Author 夏秋初
 * @Date 2021/8/13 10:24
 */
@Mapper
public interface ArticleMapper {
    public ArticleEntity findById(Integer id);
    public List<ArticleEntity> findByPaging(Map param);
    public Integer add(ArticleEntity articleEntity);
    public Integer update(ArticleEntity articleEntity);
    public Integer delete(Integer id);
}

4. 文章 service service/ArticleService.java

/**
 * @Author 夏秋初
 * @Date 2021/8/13 10:24
 */
@Service
public class ArticleService {
    @Autowired
    ArticleMapper articleMapper;
    public ArticleEntity findById(Integer id){
        return articleMapper.findById(id);
    }

    /**
     * 分页查询
     * @param pageNum
     * @param pageSize
     * @param map
     * @return
     */
    public PageInfo findByPaging(Integer pageNum, Integer pageSize,Map map){
        PageHelper.startPage(pageNum, pageSize);
        List<ArticleEntity> articleEntityPage = articleMapper.findByPaging(map);
        PageInfo pageInfo = new PageInfo(articleEntityPage);
        return pageInfo;
    }

    /**
     * 创建一个文章
     * @param articleAddDto
     * @return
     */
    public ArticleEntity add(ArticleAddDto articleAddDto){
        ArticleEntity articleEntity = new ArticleEntity();
        articleEntity.setTitle(articleAddDto.getTitle());
        articleEntity.setIntroduction(articleAddDto.getIntroduction());
        articleEntity.setContent(articleAddDto.getContent());
        Date date = new Date();
        articleEntity.setCreatedAt(date);
        articleEntity.setUpdatedAt(date);
        articleMapper.add(articleEntity);
        return articleEntity;
    }

    /**
     *  更新一个文章
     * @param articleUpdateDto
     * @return
     */
    public ArticleEntity update( Integer id,ArticleUpdateDto articleUpdateDto){
        ArticleEntity articleEntity = new ArticleEntity();
        articleEntity.setId(id);
        articleEntity.setTitle(articleUpdateDto.getTitle());
        articleEntity.setIntroduction(articleUpdateDto.getIntroduction());
        articleEntity.setContent(articleUpdateDto.getContent());
        articleEntity.setUpdatedAt(new Date());
        articleMapper.update(articleEntity);
        return articleEntity;
    }
    public Integer delete( Integer id){
        return articleMapper.delete(id);
    }
}

5. 文章控制器

/**
 * @Author 夏秋初
 * @Date 2021/8/13 10:26
 */
@RestController
@RequestMapping("admin/v1/article")
public class ArticleController {
    @Autowired
    ArticleService articleService;

    /**
     * 获取文章分页
     * @param pageNum
     * @param pageSize
     * @return
     */
    @GetMapping(value = "", produces = "application/json;charset=UTF-8")
    public ResponseEntity<CustomResponseStructureDto<PageInfo>> list(@RequestParam(name = "page_num", defaultValue = "1") Integer pageNum, @RequestParam(name = "page_size",defaultValue = "10") Integer pageSize){
        Map<String, String> map = new HashMap<>();
        PageInfo pageInfo = articleService.findByPaging(pageNum, pageSize, map);
        return ResponseEntity.ok(new CustomResponseStructureDto(0, pageInfo, "成功"));
    }

    /**
     * 获取指定id
     * @param id
     * @return
     */
    @GetMapping(value = "{id}", produces = "application/json;charset=UTF-8")
    public ResponseEntity<CustomResponseStructureDto<ArticleEntity>> list(@PathVariable("id") Integer id){
        ArticleEntity article = articleService.findById(id);
        return ResponseEntity.ok(new CustomResponseStructureDto<ArticleEntity>(0, article, "成功"));
    }

    /**
     * 新增文章
     * @param articleAddDto
     * @return
     */
    @PostMapping(value = "", produces = "application/json;charset=UTF-8")
    public ResponseEntity<CustomResponseStructureDto<ArticleEntity>> add(@RequestBody ArticleAddDto articleAddDto){
        return ResponseEntity.ok(new CustomResponseStructureDto<ArticleEntity>(0, articleService.add(articleAddDto), ""));
    }

    /**
     * 更新文章
     * @param id
     * @param articleUpdateDto
     * @return
     */
    @PutMapping(value = "{id}", produces = "application/json;charset=UTF-8")
    public ResponseEntity<CustomResponseStructureDto<ArticleEntity>> add(@PathVariable("id") Integer id, @RequestBody ArticleUpdateDto articleUpdateDto){
        return ResponseEntity.ok(new CustomResponseStructureDto<ArticleEntity>(0, articleService.update(id, articleUpdateDto), ""));
    }

    /**
     * 删除文章
     * @param id
     * @return
     */
    @DeleteMapping(value = "{id}", produces = "application/json;charset=UTF-8")
    public ResponseEntity<CustomResponseStructureDto<Object>> delete(@PathVariable("id") Integer id){
        articleService.delete(id);
        return ResponseEntity.ok(new CustomResponseStructureDto<Object>(0, null , ""));
    }
}