=============
后端_评论列表
=============

1 数据库表

1.1 评论表

CREATE TABLE `ysdblogdb`.`t_comment`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `content` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NOT NULL,
  `create_date` bigint(0) NOT NULL,
  `article_id` bigint(0) NOT NULL,
  `author_id` bigint(0) NOT NULL,
  `parent_id` bigint(0) NOT NULL,
  `to_uid` bigint(0) NOT NULL,
  `level` varchar(1) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `article_id`(`article_id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

2 实体类

2.1 评论实体类

/ysdblog-api/src/main/java/com/weihome/ysdblog/dao/pojo/Comment.java：

@Data
public class Comment {
    private Long id;
    private String content;
    private Long createDate;
    private Long articleId;
    private Long authorId;
    private Long parentId;
    private Long toUid;
    private Integer level;
}

3 数据访问接口

3.1 评论数据访问接口

/ysdblog-api/src/main/java/com/weihome/ysdblog/dao/mapper/CommentMapper.java：

public interface CommentMapper extends BaseMapper<Comment> {
}

4 视图对象

4.1 评论视图对象

/ysdblog-api/src/main/java/com/weihome/ysdblog/vo/CommentVo.java：

@Data
public class CommentVo  {
    // 基于雪花算法自动生成的分布式ID可能很大
    // 在Json中以数值形式表示可能导致前端损失精度
    // 加此注解显式指明该属性在Json中以字符串形式表达
    @JsonSerialize(using = ToStringSerializer.class)
    private Long id;
    private String content;
    private String createDate;
    private UserVo author;
    private List<CommentVo> children;
    private UserVo toUser;
    private Integer level;
}

5 评论服务

5.1 评论服务接口

/ysdblog-api/src/main/java/com/weihome/ysdblog/service/CommentService.java：

public interface CommentService {
    /**
     * 根据文章ID查询评论列表
     */
    Result list(Long articleId);
}

5.2 评论服务实现

/ysdblog-api/src/main/java/com/weihome/ysdblog/service/impl/CommentServiceImpl.java：

@Service
public class CommentServiceImpl implements CommentService {
    @Autowired
    CommentMapper commentMapper;

    @Autowired
    UserService userService;

    @Override
    public Result list(Long articleId) {
        LambdaQueryWrapper<Comment> queryWrapper =
            new LambdaQueryWrapper<>();
        queryWrapper.eq(Comment::getArticleId, articleId);
        queryWrapper.eq(Comment::getLevel, 1); // 从顶级评论开始
        List<Comment> comments = commentMapper.selectList(queryWrapper);
        return Result.success(copyList(comments));
    }

    private List<CommentVo> copyList(List<Comment> comments) {
        List<CommentVo> commentVos = new ArrayList<>();
        for (Comment comment: comments)
            commentVos.add(copy(comment));
        return commentVos;
    }

    private CommentVo copy(Comment comment) {
        CommentVo commentVo = new CommentVo();
        BeanUtils.copyProperties(comment, commentVo);

        commentVo.setCreateDate(new DateTime(comment.getCreateDate())
            .toString("yyyy-MM-dd HH:mm:ss"));

        UserVo author = new UserVo();
        BeanUtils.copyProperties(
            userService.findUserById(comment.getAuthorId()), author);
        commentVo.setAuthor(author);

        if (comment.getLevel() == 1)
            commentVo.setChildren(
                findCommentsByParentId(comment.getId()));
        else {
            UserVo toUser = new UserVo();
            BeanUtils.copyProperties(
                userService.findUserById(comment.getToUid()), toUser);
            commentVo.setToUser(toUser);
        }

        return commentVo;
    }

    private List<CommentVo> findCommentsByParentId(Long parentId) {
        LambdaQueryWrapper<Comment> queryWrapper =
            new LambdaQueryWrapper<>();
        queryWrapper.eq(Comment::getParentId, parentId);
        queryWrapper.eq(Comment::getLevel, 2);
        return copyList(commentMapper.selectList(queryWrapper));
    }
}

6 评论控制器

/ysdblog-api/src/main/java/com/weihome/ysdblog/controller/CommentController.java：

@RestController
@RequestMapping("comment")
public class CommentController {
    @Autowired
    private CommentService commentService;
    /**
     * 根据文章ID查询评论列表
     */
    @GetMapping("list/{articleId}")
    public Result list(@PathVariable Long articleId) {
        return commentService.list(articleId);
    }
}

7 运行测试

Postman
    GET
        localhost:8888/comment/list/1511577146642972674
-------------------------------------------------------
{
    "success": true,
    "code": 200,
    "msg": "success",
    "data": [
        {
            "id": "1511582322946785281",
            "content": "comment_a",
            "createDate": "2022-04-06 13:51:24",
            "author": {
                "id": 1511575239857848321,
                "account": "user_a",
                "avatar": "/static/img/logo.b3a48c0.png",
                "nickname": "nickname_a"
            },
            "children": [
                {
                    "id": "1511582783766577154",
                    "content": "comment_b",
                    "createDate": "2022-04-06 13:53:14",
                    "author": {
                        "id": 1511575239857848321,
                        "account": "user_a",
                        "avatar": "/static/img/logo.b3a48c0.png",
                        "nickname": "nickname_a"
                    },
                    "children": null,
                    "toUser": {
                        "id": 1511575239857848321,
                        "account": "user_a",
                        "avatar": "/static/img/logo.b3a48c0.png",
                        "nickname": "nickname_a"
                    },
                    "level": 2
                }
            ],
            "toUser": null,
            "level": 1
        }
    ]
}