## 任务名称: 发布动态
### 目标:
- 掌握实体类的设计和实现
- 了解并发控制策略，重点掌握乐观锁的实现
### 预备知识:
- [JPA关联关系](../guides/JPA实体类的关联关系.md)
- [并发控制策略](../guides/并发控制策略.md)


### 操作步骤

#### 1. 写发布动态接口的API文档

- [发布动态](../api%20doc/发布动态.md)

- [根据id获取动态详情](../api%20doc/根据id获取动态详情.md)

#### 2. 完成实体类设计

根据接口文档，以及前端界面的设计，完成实体类设计.

**示例代码只包括重点的部分，其他部分可以参考项目的源码。**

**Post**

```java
@Comment("冒泡/动态/文章")
@Entity
public class Post  extends BaseAuditingEntity{
    @Version
    private Long version;

    @Comment("用户ID")
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_id")
    private User user;

    @OneToMany(mappedBy = "post", cascade = CascadeType.PERSIST, fetch = FetchType.LAZY)
    private List<PostContent> contents;

    @Comment("评论数")
    @ColumnDefault("0")
    @Column(name = "comment_count", nullable = false)
    private Long commentCount = 0L;

    @Comment("收藏数")
    @ColumnDefault("0")
    @Column(name = "collection_count", nullable = false)
    private Long collectionCount = 0L;

    @Comment("点赞数")
    @ColumnDefault("0")
    @Column(name = "upvote_count", nullable = false)
    private Long upvoteCount = 0L;

    @Comment("分享数")
    @ColumnDefault("0")
    @Column(name = "share_count", nullable = false)
    private Long shareCount = 0L;

    @Comment("可见性: 0私密 10充电可见 20订阅可见 30保留 40保留 50好友可见 60关注可见 70保留 80保留 90公开")
    @ColumnDefault("50")
    @Column(name = "visibility", nullable = false)
    private Byte visibility;

    @Comment("是否置顶")
    @ColumnDefault("0")
    @Column(name = "is_top", nullable = false)
    private Boolean isTop = false;

    @Comment("是否精华")
    @ColumnDefault("0")
    @Column(name = "is_essence", nullable = false)
    private Boolean isEssence = false;

    @Comment("是否锁定")
    @ColumnDefault("0")
    @Column(name = "is_lock", nullable = false)
    private Boolean isLock = false;

    @Comment("参与的主题")
    @Column(name = "tags")
    private String tags;

    @Comment("IP地址")
    @Column(name = "ip", length = 15)
    private String ip;

    @Comment("IP城市地址")
    @Column(name = "ip_loc", length = 64)
    private String ipLoc;

}
```

**PostContent**

```java
@Comment("冒泡/动态/文章内容")
@Entity
public class PostContent  extends  BaseAuditingEntity{
    @Comment("冒泡/动态/文章ID")
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "post_id", nullable = false)
    private Post post;

    @Comment("用户ID")
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

    @Comment("内容")
    @Column(name = "content", nullable = false, length = 4000)
    private String content;

    @Comment("类型，1标题，2文字段落，3图片地址，4视频地址，5语音地址，6链接地址，7附件资源，8收费资源")
    @ColumnDefault("2")
    @Column(name = "type", nullable = false)
    private Byte type = 2;

    @Comment("排序，越小越靠前")
    @ColumnDefault("100")
    @Column(name = "sort", nullable = false)
    private Integer sort =100;
}
```
**Tag**

```java
@Comment("标签")
@Entity
public class Tag extends BaseAuditingEntity{
    @Version
    private Long version;

    @Comment("创建者ID")
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

    @Comment("标签名")
    @Column(name = "tag", nullable = false)
    private String tag;

    @Comment("引用数")
    @ColumnDefault("0")
    @Column(name = "quote_num", nullable = false)
    private Long quoteNum = 0L;
}
```

#### 3. 为每个实体类创建其对应的JpaRepository接口

**PostRepository**

```java
public interface PostRepository extends JpaRepository<Post, Long> {
}

```
**PostContentRepository**
```java
public interface PostContentRepository extends JpaRepository<PostContent, Long> {
}
```
**TagRepository**

```java
public interface TagRepository extends JpaRepository<Tag, Long> {
    @Query("SELECT t.tag FROM Tag t WHERE t.tag LIKE CONCAT('%', :key, '%') ORDER BY t.quoteNum DESC limit 20")
    List<String> findByTagContainingOrderByQuoteNumDesc(@Param("key") String key);

    Optional<Tag> findByTag(String tag);
}
```
#### 4. 完成ResponseBody的DTO类的设计
**PostDto**
```java

@Value
public class PostDto implements Serializable {
    Long id;
    Long userId;
    Long commentCount;
    Long collectionCount;
    Long upvoteCount;
    Long shareCount;
    Byte visibility;
    Boolean isTop;
    Boolean isEssence;
    Boolean isLock;
    Long latestRepliedOn;
    String tags;
    Long attachmentPrice;
    String ip;
    String ipLoc;
    @JsonSerialize(using = MillisecondToSecondSerializer.class)
    Long createdOn;
    @JsonSerialize(using = MillisecondToSecondSerializer.class)
    Long modifiedOn;
    Long deletedOn;
    Byte isDel;
    UserDto user;
    List<PostContentDto> contents;
}
```

**PostContentDto**

```java
@Value
public class PostContentDto implements Serializable {
    Long id;
    Long postId;
    String content;
    Byte type;
    Integer sort;
    @JsonSerialize(using = MillisecondToSecondSerializer.class)
    Long createdOn;
    @JsonSerialize(using = MillisecondToSecondSerializer.class)
    Long modifiedOn;
}
```

**TagDto**
```java
@Value
public class TagDto implements Serializable {
    Long id;
    Long userId;
    UserDto user;
    String tag;
    Long quoteNum;
    Long createdOn;
    Long modifiedOn;
}
```

#### 5. 完成RequestBody的DTO类的设计

**PostRequest**
```java
@Setter
@Getter
public class PostRequest {
    private Long attachmentPrice;
    private Byte visibility;
    //帖子内容列表
    List<ContentInPostRequest> contents;
    // #标签列表
    List<String> tags;
    // @用户列表
    List<String> users;
}
```

**ContentInPostRequest**
```java
@Setter
@Getter
public class ContentInPostRequest {
    private String content;
    private Integer sort;
    private Byte type;
}
```
#### 6. 完成MapStruct的Mapper接口

**PostMapper**

```java
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE, componentModel = MappingConstants.ComponentModel.SPRING)
public interface PostMapper {
    Post toEntity(PostDto postDto);

    PostDto toDto(Post post);

    @BeanMapping(nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE)
    Post partialUpdate(PostDto postDto, @MappingTarget Post post);
}
```
**PostContentMapper**
```java
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE, componentModel = MappingConstants.ComponentModel.SPRING)
public interface PostContentMapper {
    PostContent toEntity(PostContentDto postContentDto);

    PostContentDto toDto(PostContent postContent);

    @BeanMapping(nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE)
    PostContent partialUpdate(PostContentDto postContentDto, @MappingTarget PostContent postContent);
}
```

**TagMapper**
```java
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE, componentModel = MappingConstants.ComponentModel.SPRING)
public interface TagMapper {
    Tag toEntity(TagDto tagDto);

    @Mapping(source = "user.id", target = "userId")
    @Mapping(source = "user", target = "user")
    TagDto toDto(Tag tag);

    @BeanMapping(nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE)
    Tag partialUpdate(TagDto tagDto, @MappingTarget Tag tag);
}
```

#### 7. 完成PostService中发布动态的实现

创建PostService类，实现createPost方法。

```java 
    /**
     * 处理文章发布请求
     * @param postRequest 创建文章的请求参数
     * @return 创建成功后的文章DTO
     */
    public PostDto handlePostRequest(PostRequest postRequest){
        // 获取当前用户
        User user = authService.getCurrentUser();
        // 保存文章
        Post post = savePost(postRequest, user);
        // 处理post中的标签
        handleTags(postRequest, user);
        // 发送消息通知post中@的用户
        handleAtUser(postRequest, user);
    
        return postMapper.toDto(post);
    }
    
    private Post savePost(PostRequest postRequest, User currentUser){
        Post post = new Post();
        post.setUser(currentUser);
        // 设置附件价格，默认为0
        post.setAttachmentPrice(postRequest.getAttachmentPrice()!=null?postRequest.getAttachmentPrice():0);
        // 设置文章可见性
        post.setVisibility(postRequest.getVisibility());
        // 文章内容
        List<PostContent> contents = new ArrayList<>();
        postRequest.getContents().forEach(contentReq -> {
            PostContent content = new PostContent();
            content.setContent(contentReq.getContent());  // 设置内容
            content.setSort(contentReq.getSort());  // 设置排序
            content.setType(contentReq.getType());  // 设置类型
            content.setPost(post);  // 关联文章
            content.setUser(currentUser);  // 关联用户
            contents.add(content);  // 添加到列表
        });
        post.setContents(contents);
        // 保存文章
        return postRepository.save(post);
    }

    private void handleTags(PostRequest postRequest, User currentUser){
        // 处理post中的标签
        postRequest.getTags().forEach((tag)->{
            Tag tagEntity = tagRepository.findByTag(tag).orElse(null);
            if(tagEntity==null){
                // 如果标签不存在，则创建新标签并关联文章
                tagEntity = new Tag();
                tagEntity.setTag(tag);
                tagEntity.setUser(currentUser);
                tagEntity.setQuoteNum(1L);
                tagRepository.save(tagEntity);
            }else{
                // 如果标签已存在，则更新引用次数
                try {
                    tagEntity.setQuoteNum(tagEntity.getQuoteNum() + 1L);
                    tagRepository.save(tagEntity); // Spring Data JPA 自动处理乐观锁
                } catch (OptimisticLockingFailureException e) {
                    // 处理乐观锁失败的情况，如重新获取实体并重试或记录日志等
                    log.error("Optimistic locking failed for tag: {}", tagEntity.getTag(), e);
                    // TODO： 可添加重试逻辑
                    // 简单处理为继续抛出异常，让此次发帖失败
                    throw e;
                }

            }
        });
    }

    private void handleAtUser(PostRequest postRequest, User currentUser){
        postRequest.getUsers().forEach((username)->{
            User toUser = userRepository.findByUsername(username).orElseThrow(()->new ResourceNotFoundException("User","username="+username));
            // TODO: 发送消息通知toUser
        });
    }
```
#### 8. 完成PostController中发布动态的实现 
创建PostController类，实现createPost方法。
```java
    @PostMapping("/post")
    public DataResult<PostDto> createPost(@RequestBody PostRequest postRequest) {
        return ResultUtil.ok(postService.createPost(postRequest));
    }
```

#### 9. 实现根据id获取动态功能

在PostService类中添加getPost方法。  

```java
    /**
     * 根据文章ID获取文章详情
     * @param id 文章ID
     * @return 文章DTO
     */
    public PostDto getPost(Long id){
       Post post = postRepository.findById(id).orElseThrow(()->new ResourceNotFoundException("Post","id="+id));
       return postMapper.toDto(post);
    }
```

在PostController类中添加getPost方法。
```java
    @GetMapping("/post")
    public DataResult<PostDto> getPost(@PathParam("id") Long id) {
        return ResultUtil.ok(postService.getPost(id));
    }
```
#### 10. 通过前端完成发布动态

- 运行vue前端项目
- 在浏览器中访问http://localhost:5173
- 登录账号
- 完成发布动态: 上传图片、内容中支持#主题 


### 技术/工具需求:
-  [ip2region](https://github.com/lionsoul2014/ip2region) 根据ip地址获取用户所在地

### 成功标准:
- 通过paopao ce的vue前端完成发布动态功能

### 扩展学习(可选):
- [提供一些额外学习资源或挑战性任务，鼓励学有余力的学生进一步探索。]

### 评估与反馈:
- [说明如何提交作业、代码审查的标准、或任何反馈收集机制。]

### 时间估算:
- 4 Hours