问答社区-关注列表、粉丝列表

需求：

业务层

• 查询某个用户关注的人，支持分页
• 查询某个用户的粉丝，支持分页

表现层

• 处理“查询关注的人”、“查询粉丝”请求
• 编写“查询关注的人”、“查询粉丝”模板

1、followService新增，查询粉丝列表、关注列表的方法，返回list

//查询某用户关注的人
    public List<Map<String, Object>> findFollowees(int userId, int offset, int limit) {
        String followeeKey = RedisKeyUtil.getFolloweeKey(userId, ENTITY_TYPE_USER);
        Set<Integer> targetIds = redisTemplate.opsForZSet().reverseRange(followeeKey, offset, offset + limit - 1);

        if (targetIds == null) {
            return null;
        }

        List<Map<String, Object>> list = new ArrayList<>();
        for (Integer targetId : targetIds) {
            Map<String, Object> map = new HashMap<>();
            User user = userService.findUserById(targetId);
            map.put("user", user);
            Double score = redisTemplate.opsForZSet().score(followeeKey, targetId);
            map.put("followTime", new Date(score.longValue()));
            list.add(map);
        }
        return list;

    }


    //查询某用户的粉丝
    public List<Map<String, Object>> findFollowers(int userId, int offset, int limit) {
        String followerKey = RedisKeyUtil.getFollowerKey(ENTITY_TYPE_USER, userId);
        Set<Integer> targetIds = redisTemplate.opsForZSet().reverseRange(followerKey, offset, offset + limit - 1);

        if (targetIds == null) {
            return null;
        }

        List<Map<String, Object>> list = new ArrayList<>();
        for (Integer targetId : targetIds) {
            Map<String, Object> map = new HashMap<>();
            User user = userService.findUserById(targetId);
            map.put("user", user);
            Double score = redisTemplate.opsForZSet().score(followerKey, targetId);
            map.put("followTime", new Date(score.longValue()));
            list.add(map);
        }
        return list;

    }

2、controller处理“查询关注的人”、“查询粉丝”请求

//关注列表
    @RequestMapping(value = "/followees/{userId}", method = RequestMethod.GET)
    public String getFollowees(@PathVariable("userId") int userId, Model model, Page page) {
        User user = userService.findUserById(userId);
        if (user == null) {
            throw new RuntimeException("该用户不存在!");
        }
        model.addAttribute("user", user);

        page.setLimit(7);
        page.setPath("/followees/" + userId);
        page.setRows((int) followService.findFolloweeCount(userId, ENTITY_TYPE_USER));

        List<Map<String, Object>> followees = followService.findFollowees(userId, page.getOffset(), page.getLimit());
        if (followees != null) {
            for (Map<String, Object> map : followees) {
                User u = (User) map.get("user");
                map.put("hasFollowed", hasFollowed(u.getId()));
                System.out.println(u.toString());
            }
        }
        model.addAttribute("users", followees);
        return "/site/followee";
    }

    //粉丝列表
    @RequestMapping(value = "/followers/{userId}", method = RequestMethod.GET)
    public String getFollowers(@PathVariable("userId") int userId, Model model, Page page) {
        User user = userService.findUserById(userId);
        if (user == null) {
            throw new RuntimeException("该用户不存在!");
        }
        model.addAttribute("user", user);

        page.setLimit(7);
        page.setPath("/followers/" + userId);
        page.setRows((int) followService.findFollowerCount(ENTITY_TYPE_USER, userId));

        List<Map<String, Object>> followers = followService.findFollowers(userId, page.getOffset(), page.getLimit());
        if (followers != null) {
            for (Map<String, Object> map : followers) {
                User u = (User) map.get("user");
                map.put("hasFollowed", hasFollowed(u.getId()));
            }
        }
        model.addAttribute("users", followers);
        return "/site/follower";
    }

    private boolean hasFollowed(int userId) {
        if (hostHolder.getUser() == null) {
            return false;
        }
        return followService.hasFollowed(hostHolder.getUser().getId(), ENTITY_TYPE_USER, userId);
    }

3、表现层页面

<div class="position-relative">
                    <!-- 选项 -->
                    <ul class="nav nav-tabs mb-3">
                        <li class="nav-item">
                            <a class="nav-link position-relative active" th:href="@{|/followees/${user.id}|}">
                                <i class="text-info" th:utext="${user.username}">Nowcoder</i> 关注的人</a>
                        </li>
                        <li class="nav-item">
                            <a class="nav-link position-relative" th:href="@{|/followers/${user.id}|}">关注 <i class="text-info" th:utext="${user.username}">Nowcoder</i> 的人</a>
                        </li>
                    </ul>
                    <a th:href="@{|/user/profile/${user.id}|}" class="text-muted position-absolute rt-0">返回个人主页&gt;</a>
                </div>

                <!-- 关注列表 -->
                <ul class="list-unstyled">
                    <li class="media pb-3 pt-3 mb-3 border-bottom position-relative" th:each="map:${users}">
                        <a th:href="@{|/user/profile/${map.user.id}|}">
                            <img th:src="${map.user.headerUrl}" class="mr-4 rounded-circle user-header" alt="用户头像" >
                        </a>
                        <div class="media-body">
                            <h6 class="mt-0 mb-3">
                                <span class="text-success" th:utext="${map.user.username}">落基山脉下的闲人</span>
                                <span class="float-right text-muted font-size-12">关注于 <i th:text="${#dates.format(map.followTime,'yyyy-MM-dd HH:mm:ss')}">2019-04-28 14:13:25</i></span>
                            </h6>
                            <div>
                                <input type="hidden" id="entityId" th:value="${map.user.id}">
                                <button type="button" th:class="|btn ${map.hasFollowed?'btn-secondary':'btn-info'} btn-sm float-right follow-btn|"
                                        th:if="${loginUser!=null&&loginUser.id!=map.user.id}" th:text="${map.hasFollowed?'已关注':'关注TA'}">关注TA</button>
                            </div>
                        </div>
                    </li>
                </ul>

总结：
简单说就是从Redis中把数据拿出来，通过里面的userid查询到每个用户，将用户放到hashmap中，再将返回list集合
当处理前端传过来的请求的时候，先进行判断，用户是否存在，在返回之前再判断是否关注了，接着再传递回模板