paopao/docs/tasks/任务11-Sprint-2-点赞和收藏动态.md

## 任务名称: 点赞和收藏动态
### 目标:
- 巩固练习： 熟练掌握基于spring boot开发的基本步骤

### 预备知识:

### 操作步骤:
#### 1. API文档

[点赞和取消点赞接口](../api%20doc/点赞和取消点赞接口.md)

[获取当前用户对某个动态的点赞状态接口](../api%20doc/获取当前用户对某个动态的点赞状态接口.md)

[收藏和取消收藏接口](../api%20doc/收藏和取消收藏接口.md)

[获取当前用户对某个动态的收藏状态接口](../api%20doc/获取当前用户对某个动态的收藏状态接口.md)

#### 2. 数据模型设计和实现

##### 2.1 实体类

**PostStar**
```java
@Entity
public class PostStar extends BaseAuditingEntity{

    @Comment("POST 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;
}
```

**PostCollection**

```java
@Entity
public class PostCollection extends BaseAuditingEntity{

    @Comment("POST 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;

}
```

##### 2.2 DTO

**PostStarDTO**
```java
@Value
public class PostStarDto {
    Long id;
    PostDto post;
    UserDto user;
    @JsonSerialize(using = MillisecondToSecondSerializer.class)
    Long createdOn;
    @JsonSerialize(using = MillisecondToSecondSerializer.class)
    Long modifiedOn;
}

```
**PostCollectionDTO**

```java
@Value
public class PostCollectionDto {

    Long id;
    PostDto post;
    UserDto user;
    @JsonSerialize(using = MillisecondToSecondSerializer.class)
    Long createdOn;
    @JsonSerialize(using = MillisecondToSecondSerializer.class)
    Long modifiedOn;
}

```

##### 2.3 Mapper

**PostStarMapper**

```java
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE, componentModel = MappingConstants.ComponentModel.SPRING)
public interface PostStarMapper {
    PostStar toEntity(PostStarDto postStarDto);

    PostStarDto toDto(PostStar postStar);

    @BeanMapping(nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE)
    PostStar partialUpdate(PostStarDto postStarDto, @MappingTarget PostStar postStar);
}
```

**PostCollectionMapper**
```java

@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE, componentModel = MappingConstants.ComponentModel.SPRING)
public interface PostCollectionMapper {
    PostCollection toEntity(PostCollectionDto postCollectionDto);

    PostCollectionDto toDto(PostCollection postCollection);

    @BeanMapping(nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE)
    PostCollection partialUpdate(PostCollectionDto postCollectionDto, @MappingTarget PostCollection postCollection);
}

```


#### 3. JPA接口

**PostStarRepository**
```java

public interface PostStarRepository extends JpaRepository<PostStar, Long> {
    Optional<PostStar> findByUserIdAndPostId(Long postId, Long userId);
}
```

**PostCollectionRepository**
```java


public interface PostCollectionRepository extends JpaRepository<PostCollection, Long> {
    Optional<PostCollection> findByUserIdAndPostId(Long userId, Long postId);
}
```

#### 4. 业务逻辑

在PostService中添加处理点赞的方法：

```java

/**
     * 判断当前用户是对指定文章否已点赞
     * @param postId
     * @return
     */
    public boolean currentUserHasStarred(Long postId){
        User user = authService.getCurrentUser();
        return postStarRepository.findByUserIdAndPostId(user.getId(), postId).isPresent();
    }

    /**
     * 点赞文章
     * @param postId 文章ID
     * @return 如果点赞成功返回true，如果已点过赞则返回false
     */
    public boolean toggleStar(long postId){
        // 获取当前用户
        User user = authService.getCurrentUser();
        // 确认文章存在
        Post post = postRepository.findById(postId).orElseThrow(()->new ResourceNotFoundException("Post","id="+postId));
        // 确认用户是否已点赞
        PostStar postStar = postStarRepository.findByUserIdAndPostId(user.getId(),postId).orElse(null);
        if(postStar==null){
            // 如果未点赞，则创建点赞记录并更新文章点赞数
            postStar = new PostStar();
            postStar.setPost(post);
            postStar.setUser(user);
            postStarRepository.save(postStar);
            post.setUpvoteCount(post.getUpvoteCount()+1);
            postRepository.save(post);
            return true;
        }
        // 如果已点赞，则删除点赞记录并更新文章点赞数
        postStarRepository.delete(postStar);
        post.setUpvoteCount(post.getUpvoteCount()-1);
        postRepository.save(post);
        return false;
    }
```
对于收藏的处理与点赞类似，不再赘述。

#### 5. RestController 

在PostController中添加点赞相关的接口：
```java

    @GetMapping("/post/star")
    public DataResult<Map<String, Boolean>> currentHasStarred(@PathParam("id") Long postId) {
        Map<String, Boolean> result = new HashMap<>();
        result.put("status", postService.currentUserHasStarred(postId));
        return ResultUtil.ok(result);
    }
    @PostMapping("/post/star")
    public DataResult<Map<String, Boolean>> toggleStar(@RequestBody Map<String, Long> payload) {
        boolean stared = postService.toggleStar(payload.get("id"));
        Map<String, Boolean> result = new HashMap<>();
        result.put("status", stared);
        return ResultUtil.ok(result);
    }


```
收藏的接口与点赞类似，不再赘述。



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