潭潭 阿里技术 今天
阿里妹导读：消息类场景是表格存储（Tablestore）主推的方向之一，因其数据存储结构在消息类数据存储上具有天然优势。为了方便用户基于Tablestore为消息类场景建模，Tablestore封装Timeline模型，旨在让用户更快捷的实现消息类场景需求。在推出Timeline（v1、v2两个版本）模型以来，受到了大量用户关注。但依然会有用户困惑，“框架、结构、模型等概念介绍了这么多，该如何基于Timeline模型，实现具体场景呢？”。本文详细讲解如何实现一个简易的IM系统。
梗概
功能模块
消息存储
存储库
★ 功能：会话窗口消息展示
public List<AppMessage> fetchConversationMessage(String timelineId, long sequenceId) {TimelineStore store = timelineV2.getTimelineStoreTableInstance();TimelineIdentifier identifier = new TimelineIdentifier.Builder().addField("timeline_id", timelineId).build();ScanParameter parameter = new ScanParameter().scanBackward(sequenceId).maxCount(30);Iterator<TimelineEntry> iterator = store.createTimelineQueue(identifier).scan(parameter);List<AppMessage> appMessages = new LinkedList<AppMessage>();while (iterator.hasNext() && counter++ <= 30) {TimelineEntry timelineEntry = iterator.next();AppMessage appMessage = new AppMessage(timelineId, timelineEntry);appMessages.add(appMessage);}return appMessages;}
存储库的消息需要永久保存，是整个应用的全量消息存储。存储库数据过期时间（TTL）需要设为-1
★ 功能：多维组合、全文检索
public List<AppMessage> fetchConversationMessage(String timelineId, long sequenceId) {TimelineStore store = timelineV2.getTimelineStoreTableInstance();TimelineIdentifier identifier = new TimelineIdentifier.Builder().addField("timeline_id", timelineId).build();ScanParameter parameter = new ScanParameter().scanBackward(sequenceId).maxCount(30);Iterator<TimelineEntry> iterator = store.createTimelineQueue(identifier).scan(parameter);List<AppMessage> appMessages = new LinkedList<AppMessage>();int counter = 0;while (iterator.hasNext() && counter++ <= 30) {TimelineEntry timelineEntry = iterator.next();AppMessage appMessage = new AppMessage(timelineId, timelineEntry);appMessages.add(appMessage);}return appMessages;}
另外，为了做消息的权限管理，仅允许用户检索自己有权限查看的消息，可在消息体字段中扩展接收人ID数组，这样对所有群做检索时，需要增加接收人字段为自己的用户ID这一必要条件，即可实现消息内容的权限限制。样例中没有实现这一功能，用户可根据需求自己增加、修改。
同步库
★ 功能：新消息即时统计
public List<AppMessage> fetchSyncMessage(String userId, long lastSequenceId) {TimelineStore sync = timelineV2.getTimelineSyncTableInstance();TimelineIdentifier identifier = new TimelineIdentifier.Builder().addField("timeline_id", userId).build();ScanParameter parameter = new ScanParameter().scanForward(lastSequenceId).maxCount(30);Iterator<TimelineEntry> iterator = sync.createTimelineQueue(identifier).scan(parameter);List<AppMessage> appMessages = new LinkedList<AppMessage>();int counter = 0;while (iterator.hasNext() && counter++ <= 30) {AppMessage appMessage = new AppMessage(userId, iterator.next());appMessages.add(appMessage);}return appMessages;}
★ 功能：异步写扩散
元数据管理
★ 用户元数据
★ 功能：用户检索
通过用户ID：主键查询； 二维码（含用户ID信息）：主键查询； 用户姓名：多元索引，用户名字段设置分词字符串； 用户标签：多元索引，数组字符串索引提供签检索、嵌套索引提供多标签打分检索排序； 附近的人：多元索引，GEO索引查询附近、特定地理围栏的人；
★ 会话元数据
★ 功能：群检索
群ID：主键查询； 二维码（含用户ID信息）：主键查询； 群名：多元索引，用户名字段设置分词字符串； 群标签：多元索引，数组字符串索引提供签检索、嵌套索引提供多标签打分检索排序；
关系维护
单聊关系
★ 功能：人与单聊会话的关系
★ 功能：人与人的关系
public void establishFriendship(String userA, String userB, String timelineId) {PrimaryKey primaryKeyA = PrimaryKeyBuilder.createPrimaryKeyBuilder().addPrimaryKeyColumn("main_user", PrimaryKeyValue.fromString(userA)).addPrimaryKeyColumn("sub_user", PrimaryKeyValue.fromString(userB)).build();RowPutChange rowPutChangeA = new RowPutChange(userRelationTable, primaryKeyA);rowPutChangeA.addColumn("timeline_id", ColumnValue.fromString(timelineId));PrimaryKey primaryKeyB = PrimaryKeyBuilder.createPrimaryKeyBuilder().addPrimaryKeyColumn("main_user", PrimaryKeyValue.fromString(userB)).addPrimaryKeyColumn("sub_user", PrimaryKeyValue.fromString(userA)).build();RowPutChange rowPutChangeB = new RowPutChange(userRelationTable, primaryKeyB);rowPutChangeB.addColumn("timeline_id", ColumnValue.fromString(timelineId));BatchWriteRowRequest request = new BatchWriteRowRequest();request.addRowChange(rowPutChangeA);request.addRowChange(rowPutChangeB);syncClient.batchWriteRow(request);}public void breakupFriendship(String userA, String userB) {PrimaryKey primaryKeyA = PrimaryKeyBuilder.createPrimaryKeyBuilder().addPrimaryKeyColumn("main_user", PrimaryKeyValue.fromString(userA)).addPrimaryKeyColumn("sub_user", PrimaryKeyValue.fromString(userB)).build();RowDeleteChange rowPutChangeA = new RowDeleteChange(userRelationTable, primaryKeyA);PrimaryKey primaryKeyB = PrimaryKeyBuilder.createPrimaryKeyBuilder().addPrimaryKeyColumn("main_user", PrimaryKeyValue.fromString(userB)).addPrimaryKeyColumn("sub_user", PrimaryKeyValue.fromString(userA)).build();RowDeleteChange rowPutChangeB = new RowDeleteChange(userRelationTable, primaryKeyB);BatchWriteRowRequest request = new BatchWriteRowRequest();request.addRowChange(rowPutChangeA);request.addRowChange(rowPutChangeB);syncClient.batchWriteRow(request);}
群聊关系
★ 功能：群聊会话与人的关系
public List<Conversation> listMySingleConversations(String userId) {PrimaryKey start = PrimaryKeyBuilder.createPrimaryKeyBuilder().addPrimaryKeyColumn("main_user", PrimaryKeyValue.fromString(userId)).addPrimaryKeyColumn("sub_user", PrimaryKeyValue.INF_MIN).build();PrimaryKey end = PrimaryKeyBuilder.createPrimaryKeyBuilder().addPrimaryKeyColumn("main_user", PrimaryKeyValue.fromString(userId)).addPrimaryKeyColumn("sub_user", PrimaryKeyValue.INF_MAX).build();RangeRowQueryCriteria criteria = new RangeRowQueryCriteria(userRelationTable);criteria.setInclusiveStartPrimaryKey(start);criteria.setExclusiveEndPrimaryKey(end);criteria.setMaxVersions(1);criteria.setLimit(100);criteria.setDirection(Direction.FORWARD);criteria.addColumnsToGet(new String[] {"timeline_id"});GetRangeRequest request = new GetRangeRequest(criteria);GetRangeResponse response = syncClient.getRange(request);List<Conversation> singleConversations = new ArrayList<Conversation>(response.getRows().size());for (Row row : response.getRows()) {String timelineId = row.getColumn("timeline_id").get(0).getValue().asString();String subUserId = row.getPrimaryKey().getPrimaryKeyColumn("sub_user").getValue().asString();User friend = describeUser(subUserId);Conversation conversation = new Conversation(timelineId, friend);singleConversations.add(conversation);}return singleConversations;}
★ 功能：人与群聊会话的关系
public List<Conversation> listMyGroupConversations(String userId) {PrimaryKey start = PrimaryKeyBuilder.createPrimaryKeyBuilder().addPrimaryKeyColumn("user_id", PrimaryKeyValue.fromString(userId)).addPrimaryKeyColumn("group_id", PrimaryKeyValue.INF_MIN).build();PrimaryKey end = PrimaryKeyBuilder.createPrimaryKeyBuilder().addPrimaryKeyColumn("user_id", PrimaryKeyValue.fromString(userId)).addPrimaryKeyColumn("group_id", PrimaryKeyValue.INF_MAX).build();RangeRowQueryCriteria criteria = new RangeRowQueryCriteria(groupRelationGlobalIndex);criteria.setInclusiveStartPrimaryKey(start);criteria.setExclusiveEndPrimaryKey(end);criteria.setMaxVersions(1);criteria.setLimit(100);criteria.setDirection(Direction.FORWARD);criteria.addColumnsToGet(new String[] {"group_id"});GetRangeRequest request = new GetRangeRequest(criteria);GetRangeResponse response = syncClient.getRange(request);List<Conversation> groupConversations = new ArrayList<Conversation>(response.getRows().size());for (Row row : response.getRows()) {String timelineId = row.getPrimaryKey().getPrimaryKeyColumn("group_id").getValue().asString();Group group = describeGroup(timelineId);Conversation conversation = new Conversation(timelineId, group);groupConversations.add(conversation);}return groupConversations;}
即时感知
会话池方案
其他
多端同步
添加好友、入群申请
样例实操
开通服务、创建实例 获取AK 设置样例配置文件 实例支持二级索引（需要主动申请）；
开源地址
关注“阿里技术”官方公众号，并在对话框内回复“IM”，即可获得 Github 下载链接、了解更多详情。
样例配置
# mac 或 linux系统下：/home/userhome/tablestoreCong.json# windows系统下: C:\Documents and Settings\%用户名%\tablestoreCong.json{"endpoint": "http://instanceName.cn-hangzhou.ots.aliyuncs.com","accessId": "***********","accessKey": "***********************","instanceName": "instanceName"}
accessId：AK的ID，获取AK链接提供；
accessKey：AK的密码，获取AK链接提供；
instanceName：使用的实例名；
样例入口
项目结构
