仿牛客网社区项目（二十七）发送系统通知

触发事件

触发事件
- 评论后，发布通知
- 点赞后，发布通知
- 关注后，发布通知
处理事件
- 封装事件对象
- 开发事件的生产者
- 开发事件的消费者

创建对象实体

public class Event {
	//事件类型
    private String topic;
  	//消息发送方Id，1为管理消息
    private int userId;
    //实体类型，点赞，评论，关注
    private int entityType;
    //对应的实体id
    private int entityId;
    //接收方Id
    private int entityUserId;
    private Map<String, Object> data = new HashMap<>();

    public String getTopic() {
        return topic;
    }
	//链式编程
    public Event setTopic(String topic) {
        this.topic = topic;
        return this;
    }

    public int getUserId() {
        return userId;
    }

    public Event setUserId(int userId) {
        this.userId = userId;
        return this;
    }

    public int getEntityType() {
        return entityType;
    }

    public Event setEntityType(int entityType) {
        this.entityType = entityType;
        return this;
    }

    public int getEntityId() {
        return entityId;
    }

    public Event setEntityId(int entityId) {
        this.entityId = entityId;
        return this;
    }

    public int getEntityUserId() {
        return entityUserId;
    }

    public Event setEntityUserId(int entityUserId) {
        this.entityUserId = entityUserId;
        return this;
    }

    public Map<String, Object> getData() {
        return data;
    }

    public Event setData(String key, Object value) {
        this.data.put(key, value);
        return this;
    }

}

创建生产者，也就是队列消息的发送端

@Component
public class EventProduce {
    @Autowired
    private RabbitTemplate rabbitTemplate;
    //传递User对象将其转换为Json，接收方再转回object，使用序列号也可以，自行尝试
    public void send(Event event){
        rabbitTemplate.convertAndSend("X",event.getTopic(), JSONObject.toJSONString(event));
    }
}

创建消费者，也就是消息的处理者

@Slf4j
@Component
public class EventConsumer implements CommunityConstant {
    @Autowired
    private MessageService messageService;
    //三种类型消息，分别处理
    //follow队列
    @RabbitListener(queues = "QA")
    public void receiveLike(String jsonString, Channel channel){
      if(  jsonString==null||jsonString.length()==0){
          log.error("消息为空");
      }
        Event event = JSONObject.parseObject(jsonString, Event.class);
      if (event==null){
          log.error("类型转换失败");
      }
    sendMessage(event);
    }
    //comment队列
    @RabbitListener(queues = "QB")
    public void receiveComment(String jsonString, Channel channel){
        if(  jsonString==null||jsonString.length()==0){
            log.error("消息为空");
        }
        Event event = JSONObject.parseObject(jsonString, Event.class);
        if (event==null){
            log.error("类型转换失败");
        }
        sendMessage(event);

    }
    //like 队列
    @RabbitListener(queues = "QC")
    public void receiveFollow(String jsonString, Channel channel){
        if(  jsonString==null||jsonString.length()==0){
            log.error("消息为空");
        }
        Event event = JSONObject.parseObject(jsonString, Event.class);
        if (event==null){
            log.error("类型转换失败");
        }
        sendMessage(event);
    }

    public void sendMessage(Event event){
    // 发送站内通知
    Message message = new Message();
        message.setFromId(SYSTEM_USER_ID);
        message.setToId(event.getEntityUserId());
        message.setConversationId(event.getTopic());
        message.setCreateTime(new Date());

    Map<String, Object> content = new HashMap<>();
        content.put("userId", event.getUserId());
        content.put("entityType", event.getEntityType());
        content.put("entityId", event.getEntityId());

        if (!event.getData().isEmpty()) {
        for (Map.Entry<String, Object> entry : event.getData().entrySet()) {
            content.put(entry.getKey(), entry.getValue());
        }
    }
        message.setContent(JSONObject.toJSONString(content));
        messageService.addMessage(message);
}

更新一些静态变量在CommunityConstant中

 	/**
     * 主题: 评论
     */
    String TOPIC_COMMENT = "comment";

    /**
     * 主题: 点赞
     */
    String TOPIC_LIKE = "like";

    /**
     * 主题: 关注
     */
    String TOPIC_FOLLOW = "follow";

1.CommentController 更新Controller层，我们要对关注、点赞、评论三个业务层去修改方法，在其中增加事件

 ```java	
  @RequestMapping(path = "/add/{discussPostId}", method = RequestMethod.POST)
     public String addComment(@PathVariable("discussPostId") int discussPostId, Comment comment) {
         comment.setUserId(hostHolder.getUser().getId());
         comment.setStatus(0);
         comment.setCreateTime(new Date());
         commentService.addComment(comment);
 
         // 触发评论事件
         Event event = new Event()
                 .setTopic(TOPIC_COMMENT)
                 .setUserId(hostHolder.getUser().getId())
                 .setEntityType(comment.getEntityType())
                 .setEntityId(comment.getEntityId())
                 .setData("postId", discussPostId);
         if (comment.getEntityType() == ENTITY_TYPE_POST) {
             DiscussPost target = discussPostService.getDiscussPostById(comment.getEntityId());
             event.setEntityUserId(target.getUserId());
         } else if (comment.getEntityType() == ENTITY_TYPE_COMMENT) {
             Comment target = commentService.findCommentById(comment.getEntityId());
             event.setEntityUserId(target.getUserId());
         }
         eventProduce.send(event);
 
         return "redirect:/discuss/detail/" + discussPostId;
     }
 
 ```

2.LikeController

 @RequestMapping(path = "/like", method = RequestMethod.POST)
    @ResponseBody
    //此处未限制未登录点赞，会抛异常 可以采用之前的全局异常注解，后期会对代码重构 增加SpringSecurity框架权限控制
    public String like(int entityType, int entityId, int entityUserId,int postId) {
        User user = hostHolder.getUser();

        // 点赞
        likeService.like(user.getId(), entityType, entityId, entityUserId);

        // 数量
        long likeCount = likeService.findEntityLikeCount(entityType, entityId);
        // 状态
        int likeStatus = likeService.findEntityLikeStatus(user.getId(), entityType, entityId);
        // 返回的结果
        Map<String, Object> map = new HashMap<>();
        map.put("likeCount", likeCount);
        map.put("likeStatus", likeStatus);
        // 触发点赞事件
        if (likeStatus == 1) {
            Event event = new Event()
                    .setTopic(TOPIC_LIKE)
                    .setUserId(hostHolder.getUser().getId())
                    .setEntityType(entityType)
                    .setEntityId(entityId)
                    .setEntityUserId(entityUserId)
                    .setData("postId", postId);
            eventProduce.send(event);
        }

        return CommunityUtil.getJSONString(0, null, map);
    }

3.FollowController


    @RequestMapping(path = "/follow", method = RequestMethod.POST)
    @ResponseBody
    public String follow(int entityType, int entityId) {
        User user = hostHolder.getUser();

        followService.follow(user.getId(), entityType, entityId);
        // 触发关注事件
        Event event = new Event()
                .setTopic(TOPIC_FOLLOW)
                .setUserId(hostHolder.getUser().getId())
                .setEntityType(entityType)
                .setEntityId(entityId)
                .setEntityUserId(entityId);
        eventProduce.send(event);

        return CommunityUtil.getJSONString(0, "已关注!");
    }