发送系统通知

1、entity包下，封装时间对象：Event

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Event {
    private String topic;
    private int userId;
    // 目标实体
    private int entityType;
    private int entityId;
    // 目标实体的拥有者
    private int entityUserId;
    // 封装其他数据，用于扩展
    private Map<String,Object> data = new HashMap<>(16);

    public String getTopic() {
        return topic;
    }

    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;
    }

}

2、event包下事件生产者：EventProducer

@Component
public class EventProducer {

    @Autowired
    private KafkaTemplate kafkaTemplate;

    // 处理事件
    public void fireEvent(Event event){
        // 将事件发布到指定的主题(评论、点赞、关注)
        kafkaTemplate.send(event.getTopic(), JSONObject.toJSONString(event));
    }
}

3、event包下事件消费者：EventConsumer

@Component
public class EventConsumer implements CommunityConstant {

    private static final Logger logger = LoggerFactory.getLogger(EventConsumer.class);

    @Autowired
    private MessageService messageService;

    @KafkaListener(topics = {TOPIC_COMMENT, TOPIC_LIKE, TOPIC_FOLLOW})
    public void handleCommentMessage(ConsumerRecord record){

        if (record == null || record.value() == null) {
            logger.error("消息的内容为空");
            return;
        }

        Event event = JSONObject.parseObject(record.value().toString(), Event.class);
        if (event == null) {
            logger.error("消息格式错误!");
        }

        // 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);
    }
}

站内通知Message：

@Data
@AllArgsConstructor
@NoArgsConstructor
public class  Message {
    private int id;
    private int fromId;
    private int toId;
    private String conversationId;
    private String content;
    private int status;
    private Date createTime;
}

4、Controller层触发事件（评论、点赞、关注）

CommentController

    @RequestMapping(path = "/add/{discussPostId}", method = RequestMethod.POST)// 为了重定向用
    public String addComment(@PathVariable("discussPostId") int discussPostId, Comment 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.findDiscussPostById(comment.getEntityId());
            event.setEntityUserId(target.getUserId());
        } else if (comment.getEntityType() == ENTITY_TYPE_COMMENT) {
            Comment target = commentService.findCommentById(comment.getEntityId());
            event.setEntityUserId(target.getUserId());
        }
        eventProducer.fireEvent(event);

        return "redirect:/discuss/detail/" + discussPostId;

LikeController

    @RequestMapping(path = "/like", method = RequestMethod.POST)
    @ResponseBody
    public String like(int entityType, int entityId, int entityUserId, int postId) {// 这个参数要从页面传过来，然后处理页面
 
		......

        // 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);
            eventProducer.fireEvent(event);
        }

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

FollowController

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

		.......

        // 触发关注事件
        Event event = new Event()
                .setTopic(TOPIC_FOLLOW)
                .setUserId(hostHolder.getUser().getId())
                .setEntityType(entityType)
                .setEntityId(entityId)
                .setEntityUserId(entityId);
        eventProducer.fireEvent(event);

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

显示系统通知

1、MessageMapper

    // 查询某个主题下最新的通知
    Message selectLatestNotice(int userId, String topic);

    // 查询某个主题所包含的通知数量
    int selectNoticeCount(int userId, String topic);

    // 查询未读的通知的数量
    int selectNoticeUnreadCount(int userId, String topic);

    // 查询某个主题所包含的通知列表
    List<Message> selectNotices(int userId, String topic, int offset, int limit);

对应xml

    <select id="selectLatestNotice" resultType="Message">
        select <include refid="selectFields"></include>
        from message
        where id in (
            select max(id) from message
            where status != 2
            and from_id = 1
            and to_id = #{userId}
            and conversation_id = #{topic}
        )
    </select>

    <select id="selectNoticeCount" resultType="int">
        select count(id) from message
        where status != 2
        and from_id = 1
        and to_id = #{userId}
        and conversation_id = #{topic}
    </select>

    <select id="selectNoticeUnreadCount" resultType="int">
        select count(id) from message
        where status = 0
        and from_id = 1
        and to_id = #{userId}
        <if test="topic!=null">
            and conversation_id = #{topic}
        </if>
    </select>

    <select id="selectNotices" resultType="Message">
        select <include refid="selectFields"></include>
        from message
        where status != 2
        and from_id = 1
        and to_id = #{userId}
        and conversation_id = #{topic}
        order by create_time desc
        limit #{offset}, #{limit}
    </select>

2、MessageService

    public Message findLatestNotice(int userId, String topic) {
        return messageMapper.selectLatestNotice(userId, topic);
    }

    public int findNoticeCount(int userId, String topic) {
        return messageMapper.selectNoticeCount(userId, topic);
    }

    public int findNoticeUnreadCount(int userId, String topic) {
        return messageMapper.selectNoticeUnreadCount(userId, topic);
    }

    public List<Message> findNotices(int userId, String topic, int offset, int limit) {
        return messageMapper.selectNotices(userId, topic, offset, limit);
    }

3、MessageController列表和详情页

@RequestMapping(path = "/notice/list", method = RequestMethod.GET)
    public String getNoticeList(Model model) {
        User user = hostHolder.getUser();

        // 查询评论类通知
        Message message = messageService.findLatestNotice(user.getId(), TOPIC_COMMENT);
        Map<String, Object> messageVO = new HashMap<>();
        if (message != null) {
            messageVO.put("message", message);

            String content = HtmlUtils.htmlUnescape(message.getContent());
            Map<String, Object> data = JSONObject.parseObject(content, HashMap.class);

            messageVO.put("user", userService.findUserById((Integer) data.get("userId")));
            messageVO.put("entityType", data.get("entityType"));
            messageVO.put("entityId", data.get("entityId"));
            messageVO.put("postId", data.get("postId"));

            int count = messageService.findNoticeCount(user.getId(), TOPIC_COMMENT);
            messageVO.put("count", count);

            int unread = messageService.findNoticeUnreadCount(user.getId(), TOPIC_COMMENT);
            messageVO.put("unread", unread);
        }
        model.addAttribute("commentNotice", messageVO);

        // 查询点赞类通知
        message = messageService.findLatestNotice(user.getId(), TOPIC_LIKE);
        messageVO = new HashMap<>();
        if (message != null) {
            messageVO.put("message", message);

            String content = HtmlUtils.htmlUnescape(message.getContent());
            Map<String, Object> data = JSONObject.parseObject(content, HashMap.class);

            messageVO.put("user", userService.findUserById((Integer) data.get("userId")));
            messageVO.put("entityType", data.get("entityType"));
            messageVO.put("entityId", data.get("entityId"));
            messageVO.put("postId", data.get("postId"));

            int count = messageService.findNoticeCount(user.getId(), TOPIC_LIKE);
            messageVO.put("count", count);

            int unread = messageService.findNoticeUnreadCount(user.getId(), TOPIC_LIKE);
            messageVO.put("unread", unread);
        }
        model.addAttribute("likeNotice", messageVO);

        // 查询关注类通知
        message = messageService.findLatestNotice(user.getId(), TOPIC_FOLLOW);
        messageVO = new HashMap<>();
        if (message != null) {
            messageVO.put("message", message);

            String content = HtmlUtils.htmlUnescape(message.getContent());
            Map<String, Object> data = JSONObject.parseObject(content, HashMap.class);

            messageVO.put("user", userService.findUserById((Integer) data.get("userId")));
            messageVO.put("entityType", data.get("entityType"));
            messageVO.put("entityId", data.get("entityId"));

            int count = messageService.findNoticeCount(user.getId(), TOPIC_FOLLOW);
            messageVO.put("count", count);

            int unread = messageService.findNoticeUnreadCount(user.getId(), TOPIC_FOLLOW);
            messageVO.put("unread", unread);
        }
        model.addAttribute("followNotice", messageVO);

        // 查询未读消息数量
        int letterUnreadCount = messageService.findLetterUnreadCount(user.getId(), null);
        model.addAttribute("letterUnreadCount", letterUnreadCount);
        int noticeUnreadCount = messageService.findNoticeUnreadCount(user.getId(), null);
        model.addAttribute("noticeUnreadCount", noticeUnreadCount);

        return "/site/notice";
    }

    @RequestMapping(path = "/notice/detail/{topic}", method = RequestMethod.GET)
    public String getNoticeDetail(@PathVariable("topic") String topic, Page page, Model model) {
        User user = hostHolder.getUser();

        page.setLimit(5);
        page.setPath("/notice/detail/" + topic);
        page.setRows(messageService.findNoticeCount(user.getId(), topic));

        List<Message> noticeList = messageService.findNotices(user.getId(), topic, page.getOffset(), page.getLimit());
        List<Map<String, Object>> noticeVoList = new ArrayList<>();
        if (noticeList != null) {
            for (Message notice : noticeList) {
                Map<String, Object> map = new HashMap<>();
                // 通知
                map.put("notice", notice);
                // 内容
                String content = HtmlUtils.htmlUnescape(notice.getContent());
                Map<String, Object> data = JSONObject.parseObject(content, HashMap.class);
                map.put("user", userService.findUserById((Integer) data.get("userId")));
                map.put("entityType", data.get("entityType"));
                map.put("entityId", data.get("entityId"));
                map.put("postId", data.get("postId"));
                // 通知作者
                map.put("fromUser", userService.findUserById(notice.getFromId()));

                noticeVoList.add(map);
            }
        }
        model.addAttribute("notices", noticeVoList);

        // 设置已读
        List<Integer> ids = getLetterIds(noticeList);
        if (!ids.isEmpty()) {
            messageService.readMessage(ids);
        }

        return "/site/notice-detail";
    }

4、首页头部总未读消息显示：拦截器index.html

@Component
public class MessageInterceptor implements HandlerInterceptor {

    @Autowired
    private HostHolder hostHolder;

    @Autowired
    private MessageService messageService;

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        User user = hostHolder.getUser();
        if (user != null && modelAndView != null) {
            int letterUnreadCount = messageService.findLetterUnreadCount(user.getId(), null);
            int noticeUnreadCount = messageService.findNoticeUnreadCount(user.getId(), null);
            modelAndView.addObject("allUnreadCount", letterUnreadCount + noticeUnreadCount);
        }
    }
}

@Configuration//配置类，一般是生成第三方bean，这里实现接口
public class WebMvcConfig implements WebMvcConfigurer {
    @Autowired
    private MessageInterceptor messageInterceptor;
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(messageInterceptor)
                .excludePathPatterns("/**/*.css", "/**/*.js", "/**/*.png", "/**/*.jpg", "/**/*.jpeg");
    }