16、热帖排行

1、帖子分数与时间有关，而且点赞，收藏等操作是非常高频的，一般是通过定时任务计算帖子分数（分布式定时任务 Spring Quartz）
2、把分数变化的帖子放进缓存里，定时时间到对缓存里的帖子进行计算即可（Redis）

1、将需要计算分数的帖子放入Redis中

1、生成RedisKey
2、影响帖子分数操作发生时，将帖子放入Redis

RedisKeyUtil.java

    // 帖子分数
public static String getPostScoreKey() {
    
    return PREFIX_POST + SPLIT + "score";
}

DiscussPostController.java
A）发新帖时，将帖子id放入Redis(给帖子一个初始分数)：RedisKey:postId 存放在Set里。

    @PostMapping("/add")
    @ResponseBody
    public String addDiscussPost(String title, String content) {
    
    	...
        // 计算帖子分数
        String redisKey = RedisKeyUtil.getPostScoreKey();
        redisTemplate.opsForSet().add(redisKey, post.getId());
    }

B）加精、评论、点赞操作时，也将帖子放入Redis

    // 加精 HomeController.java
    @PostMapping("/wonderful")
    @ResponseBody
    public String setWonderful(int id) {
    
        discussPostService.updateStatus(id, 1);
		...
        // 计算帖子分数
        String redisKey = RedisKeyUtil.getPostScoreKey();
        redisTemplate.opsForSet().add(redisKey, id);

    }

	// 评论 CommentController.java
    @PostMapping("/add/{discussPostId}")
    public String addComment(@PathVariable("discussPostId") int discussPostId, Comment comment) {
    
        if (comment.getEntityType() == ENTITY_TYPE_POST) {
    
            ...
            // 计算帖子分数
            String redisKey = RedisKeyUtil.getPostScoreKey();
            redisTemplate.opsForSet().add(redisKey, discussPostId);
        }

2、使用Quartz实现定时任务

1、Job接口实现
quartz包下 PostScoreRefreshJob 类

public class PostScoreRefreshJob implements Job, CommunityConstant {
    

    private static final Logger LOGGER = LoggerFactory.getLogger(PostScoreRefreshJob.class);

    @Autowired
    private RedisTemplate redisTemplate;

    @Autowired
    private DiscussPostService discussPostService;

    @Autowired
    private LikeService likeService;

    @Autowired
    private ElasticsearchService elasticsearchService;

    private static final Date EPOCH;

    static {
    
        try {
    
            EPOCH = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("2014-08-01 00:00:00");
        } catch (ParseException e) {
    
            throw new RuntimeException("初始化牛客纪元失败！", e);
        }
    }

    @Override
    public void execute(JobExecutionContext context) throws JobExecutionException {
    

        String redisKey = RedisKeyUtil.getPostScoreKey();
        BoundSetOperations operations = redisTemplate.boundSetOps(redisKey);
        if (operations.size() == 0) {
    
            LOGGER.info("任务取消，没有需要刷新的帖子！");
            return;
        }
        LOGGER.info("[任务开始] 正在刷新帖子分数：" + operations.size());
        while (operations.size() > 0) {
    
            this.refresh((Integer) operations.pop());
        }
        LOGGER.info("[任务结束] 帖子分数刷新完毕！");
    }

    private void refresh(int postId) {
    
        DiscussPost post = discussPostService.findDiscussPostById(postId);

        if (post == null) {
    
            LOGGER.error("该帖子不存在：id = " + postId);
            return;
        }

        // 是否精华
        boolean wonderful = post.getStatus() == 1;
        // 评论数量
        int commentCount = post.getCommentCount();
        // 点赞数量
        long likeCount = likeService.findEntityLikeCount(ENTITY_TYPE_POST, postId);

        // 计算权重
        double w = (wonderful ? 75 : 0) + commentCount * 10 + likeCount * 2;
        // 分数 = 帖子权重 + 距离天数
        double score =
                Math.log10(Math.max(w, 1))
                        + (post.getCreateTime().getTime() - EPOCH.getTime()) / (1000 * 3600 * 24);
        // 更新帖子分数
        discussPostService.updateScore(postId, score);
        // 同步搜索数据
        post.setScore(score);
        elasticsearchService.saveDiscussPost(post);
    }
}

• 牛客纪元域：private static final Date epoch，由于epoch只需要初始化一次，在静态代码块里面进行初始化
• 使用BoundSetOperations 绑定 Key，BoundSetOperations就是一个绑定key的对象，我们可以通过这个对象来进行与key相关的操作。
• 从Redis里取数据，若没有数据，记录日志后直接返回。若Set为空，对每个postId执行 refresh 方法。
  refresh刷新一个帖子的方法：
  1、根据帖子id查找post实体
  2、判断是否加精、评论数量、点赞数量，计算分数（getTime() 得到毫秒值）
  3、更新帖子分数
  4、同步搜索数据
  5、对Quartz进行配置：时间间隔单位毫秒

对Quartz进行配置

// 配置 -> 数据库 -> 调用
@Configuration
public class QuartzConfig {
    
    // 刷新帖子分数任务
    @Bean
    public JobDetailFactoryBean postScoreRefreshJobDetail() {
    
        JobDetailFactoryBean factoryBean = new JobDetailFactoryBean();
        factoryBean.setJobClass(PostScoreRefreshJob.class);
        factoryBean.setName("postScoreRefreshJob");
        factoryBean.setGroup("communityJobGroup");
        factoryBean.setDurability(true);
        factoryBean.setRequestsRecovery(true);
        return factoryBean;
    }
    // 配置Trigger(SimpleTriggerFactoryBean, CronTriggerFactoryBean)
    @Bean
    public SimpleTriggerFactoryBean postScoreRefreshTrigger(JobDetail postScoreRefreshJobDetail) {
    
        SimpleTriggerFactoryBean factoryBean = new SimpleTriggerFactoryBean();
        factoryBean.setJobDetail(postScoreRefreshJobDetail);
        factoryBean.setName("postScoreRefreshTrigger");
        factoryBean.setGroup("communityTriggerGroup");
        factoryBean.setRepeatInterval(1000 * 60 * 5);
        factoryBean.setJobDataMap(new JobDataMap());
        return factoryBean;
    }

}

3、首页界面处理

1、按照最热对帖子进行排序
对 selectDiscussPosts方法进行重构即可

@Mapper
public interface DiscussPostMapper {
    

    List<DiscussPost> selectDiscussPosts(int userId, int offset, int limit, int orderMode); 
    // 增加了一个orderMode参数: orderMode=0 时按照“最新” 排序，orderMode=1 时按照“最热” 排序
}

discusspost-mapper.xml

    <select id="selectDiscussPosts" resultType="DiscussPost">
        select <include refid="selectFields"></include>
        from discuss_post
        where status != 2
        <if test="userId!=0">
            and user_id = #{
    userId}
        </if>
        <if test="orderMode==0">
            order by type desc, create_time desc
        </if>
        <if test="orderMode==1">
            order by type desc, score desc, create_time desc
        </if>
        limit #{
    offset}, #{
    limit}
    </select>

2、所有调用 selectDiscussPosts 的地方进行修改

3、HomeController：
从前端获取ordermode参数，并拼入 path 里返回给模板

    @RequestMapping(path = "/index", method = RequestMethod.GET)
    public String getIndexPage(Model model, Page page,
                               @RequestParam(name = "orderMode", defaultValue = "0") int orderMode) {
     
                               // 1.默认orderMode=0，比如访问首页时
        // 方法调用钱,SpringMVC会自动实例化Model和Page,并将Page注入Model.
        // 所以,在thymeleaf中可以直接访问Page对象中的数据.
        page.setRows(discussPostService.findDiscussPostRows(0));
        page.setPath("/index?orderMode=" + orderMode);  // 2.修改Page的路径，加上orderMode参数
		
		// 3.使用重构后的discussPostService
        List<DiscussPost> list = discussPostService
                .findDiscussPosts(0, page.getOffset(), page.getLimit(), orderMode);
        List<Map<String, Object>> discussPosts = new ArrayList<>();
        if (list != null) {
    
            for (DiscussPost post : list) {
    
                Map<String, Object> map = new HashMap<>();
                map.put("post", post);
                User user = userService.findUserById(post.getUserId());
                map.put("user", user);

                long likeCount = likeService.findEntityLikeCount(ENTITY_TYPE_POST, post.getId());
                map.put("likeCount", likeCount);

                discussPosts.add(map);
            }
        }
        model.addAttribute("discussPosts", discussPosts);
        model.addAttribute("orderMode", orderMode);

        return "/index";
    }

4、index.html
1）th:href 超链接修改，传入orderMode 参数
2）由orderMode 参数决定是否有 active 参数

<!-- 筛选条件 -->
<ul class="nav nav-tabs mb-3">
	<li class="nav-item">
		<a th:class="|nav-link ${orderMode==0?'active':''}|" th:href="@{/index(orderMode=0)}">最新</a>
	</li>
	<li class="nav-item">
		<a th:class="|nav-link ${orderMode==1?'active':''}|" th:href="@{/index(orderMode=1)}">最热</a>
	</li>
</ul>