• 需求
  
  
  
  • 开发关注、取消关注功能。
  
  
  • 统计用户的关注数、粉丝数。
  
  
  
  


• 关键
  
  
  
  • 若A关注了B，则A是B的Follower(粉丝)，B是A的Followee(目标)。
  
  
  • 关注的目标可以是用户、帖子、题目等，在实现时将这些目标抽象为实体。
  
  
  
  

一、增加相应的key

关注的除了用户，也可能是帖子等，生成Follower和Followee的key。

RedisKeyUtil.java

public class RedisKeyUtil {
// ...
private static final String PREFIX_FOLLOWEE = "followee";
private static final String PREFIX_FOLLOWER = "follower";

// ...
// 某个用户关注的实体
// followee:userId:entityType -> zset(entityId,now)
public static String getFolloweeKey(int userId, int entityType) {
return PREFIX_FOLLOWEE + SPLIT + userId + SPLIT + entityType;
}
// 某个实体拥有的粉丝
// follower:entityType:entityId -> zset(userId,now)
public static String getFollowerKey(int entityType, int entityId) {
return PREFIX_FOLLOWER + SPLIT + entityType + SPLIT + entityId;
}
}


二、业务层

FollowService.java

@Service
public class FollowService implements CommunityConstant {
@Autowired
private RedisTemplate redisTemplate;
@Autowired
private UserService userService;
// 关注
public void follow(int userId, int entityType, int entityId) {
redisTemplate.execute(new SessionCallback() {
@Override
public Object execute(RedisOperations operations) throws DataAccessException {
String followeeKey = RedisKeyUtil.getFolloweeKey(userId, entityType);
String followerKey = RedisKeyUtil.getFollowerKey(entityType, entityId);
operations.multi();
// 增加被关注对象
operations.opsForZSet().add(followeeKey, entityId, System.currentTimeMillis());
// 被关注对象增加关注者（粉丝）
operations.opsForZSet().add(followerKey, userId, System.currentTimeMillis());
return operations.exec();
}
});
}
// 取消关注
public void unfollow(int userId, int entityType, int entityId) {
redisTemplate.execute(new SessionCallback() {
@Override
public Object execute(RedisOperations operations) throws DataAccessException {
String followeeKey = RedisKeyUtil.getFolloweeKey(userId, entityType);
String followerKey = RedisKeyUtil.getFollowerKey(entityType, entityId);
operations.multi();
operations.opsForZSet().remove(followeeKey, entityId);
operations.opsForZSet().remove(followerKey, userId);
return operations.exec();
}
});
}

// 查询关注的实体的数量
public long findFolloweeCount(int userId, int entityType) {
String followeeKey = RedisKeyUtil.getFolloweeKey(userId, entityType);
return redisTemplate.opsForZSet().zCard(followeeKey);
}
// 查询实体的粉丝的数量
public long findFollowerCount(int entityType, int entityId) {
String followerKey = RedisKeyUtil.getFollowerKey(entityType, entityId);
return redisTemplate.opsForZSet().zCard(followerKey);
}
// 查询当前用户是否已关注该实体
public boolean hasFollowed(int userId, int entityType, int entityId) {
String followeeKey = RedisKeyUtil.getFolloweeKey(userId, entityType);
return redisTemplate.opsForZSet().score(followeeKey, entityId) != null;
}
// 查询某用户关注的人
public List> findFollowees(int userId, int offset, int limit) {
String followeeKey = RedisKeyUtil.getFolloweeKey(userId, ENTITY_TYPE_USER);
Set targetIds = redisTemplate.opsForZSet().reverseRange(followeeKey, offset, offset + limit - 1);
if (targetIds == null) {
return null;
}
List> list = new ArrayList<>();
for (Integer targetId : targetIds) {
Map 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> findFollowers(int userId, int offset, int limit) {
String followerKey = RedisKeyUtil.getFollowerKey(ENTITY_TYPE_USER, userId);
Set targetIds = redisTemplate.opsForZSet().reverseRange(followerKey, offset, offset + limit - 1);
if (targetIds == null) {
return null;
}
List> list = new ArrayList<>();
for (Integer targetId : targetIds) {
Map 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;
}
}


三、表现（视图）层

FollowController.java

@Controller
public class FollowController implements CommunityConstant {
@Autowired
private FollowService followService;
@Autowired
private HostHolder hostHolder;
@Autowired
private UserService userService;

// 关注
@RequestMapping(path = "/follow", method = RequestMethod.POST)
@ResponseBody
public String follow(int entityType, int entityId) {
User user = hostHolder.getUser();
followService.follow(user.getId(), entityType, entityId);
return CommunityUtil.getJSONString(0, "已关注!");
}

// 取消关注
@RequestMapping(path = "/unfollow", method = RequestMethod.POST)
@ResponseBody
public String unfollow(int entityType, int entityId) {
User user = hostHolder.getUser();
followService.unfollow(user.getId(), entityType, entityId);
return CommunityUtil.getJSONString(0, "已取消关注!");
}
}


修改UserConrroller获取个人主页方法，添加关注与关注者信息。

UserConrroller.java

// 个人主页
@RequestMapping(path = "/profile/{userId}", method = RequestMethod.GET)
public String getProfilePage(@PathVariable("userId") int userId, Model model) {
User user = userService.findUserById(userId);
if (user == null) {
throw new RuntimeException("该用户不存在!");
}
// 用户
model.addAttribute("user", user);
// 点赞数量
int likeCount = likeService.findUserLikeCount(userId);
model.addAttribute("likeCount", likeCount);
// 关注数量
long followeeCount = followService.findFolloweeCount(userId, ENTITY_TYPE_USER);
model.addAttribute("followeeCount", followeeCount);
// 粉丝数量
long followerCount = followService.findFollowerCount(ENTITY_TYPE_USER, userId);
model.addAttribute("followerCount", followerCount);
// 是否已关注
boolean hasFollowed = false;
if (hostHolder.getUser() != null) {
hasFollowed = followService.hasFollowed(hostHolder.getUser().getId(), ENTITY_TYPE_USER, userId);
}
model.addAttribute("hasFollowed", hasFollowed);
return "/site/profile";
}


页面处理（略）