发布订阅（PubSub）是一个功能强大的XMPP协议扩展。用户订阅一个项目（在xmpp中叫做node），得到通知时，也即当事项节点更新时。xmpp服务器通知用户（通过message格式）。
节点类型：
- Leaf node: 叶子节点，包含了发布项.
- Collection node: 可以看做集合节点，它下面包含叶子.
注意：不能订阅整个Collection node，只能订阅Leaf node
访问和发布模式 Access and Publisher Models
- Open: 任何人都能订阅
- Authorize: 订阅请求必须由所有者批准，只有认证的用户可以订阅项目。
- Whitelist: 白名单里的用户可以订阅.
- Presence: 只有能收到发布者也即Owner的即席状态的用户才能收到订阅.
- Roster: 只有在用户花名册或花名册组内的用户可以收到订阅事项提醒
在openfire里，Whitelist的配置如下：
发布者模式:
- Open: anyone may publish items to the node.（权限最大）
- Publishers: owners and publishers are allowed to publish items to the node.
- Subscribers: owners, publishers and subscribers are allowed to publish items to the node.
发布订阅的过程，发布者发布到叶子节点，订阅者收到消息提醒
XMPP中的订阅流程
1、首先，需要确认你的服务器支持pubsub特性
1.1 查询XMPP服务的所有服务
<iq type='get' from='wangxin@im/CVTalk' to='im' id='11'> <query xmlns='http://jabber.org/protocol/disco#info'/> </iq>
返回：
<iq id="11" to="wangxin@im/PC" from="im" type="result"> <query xmlns="http://jabber.org/protocol/disco#info"> <identity category="server" name="Openfire Server" type="im"/> <identity category="pubsub" name="null" type="pep"/> <feature var="http://jabber.org/protocol/pubsub#manage-subscriptions"/> <feature var="http://jabber.org/protocol/pubsub#modify-affiliations"/> <feature var="http://jabber.org/protocol/pubsub#retrieve-default"/> <feature var="http://jabber.org/protocol/pubsub#collections"/> <feature var="jabber:iq:private"/> <feature var="http://jabber.org/protocol/disco#items"/> <feature var="vcard-temp"/> <feature var="http://jabber.org/protocol/pubsub#publish"/> <feature var="urn:xmpp:archive:auto"/> <feature var="http://jabber.org/protocol/pubsub#subscribe"/> <feature var="http://jabber.org/protocol/pubsub#retract-items"/> <feature var="http://jabber.org/protocol/offline"/> <feature var="http://jabber.org/protocol/pubsub#meta-data"/> <feature var="jabber:iq:register"/> <feature var="http://jabber.org/protocol/pubsub#retrieve-subscriptions"/> <feature var="http://jabber.org/protocol/pubsub#default_access_model_open"/> <feature var="jabber:iq:roster"/> <feature var="http://jabber.org/protocol/pubsub#config-node"/> <feature var="http://jabber.org/protocol/address"/> <feature var="http://jabber.org/protocol/pubsub#publisher-affiliation"/> <feature var="http://jabber.org/protocol/pubsub#item-ids"/> <feature var="http://jabber.org/protocol/pubsub#instant-nodes"/> <feature var="http://jabber.org/protocol/commands"/> <feature var="http://jabber.org/protocol/pubsub#multi-subscribe"/> <feature var="http://jabber.org/protocol/pubsub#outcast-affiliation"/> <feature var="http://jabber.org/protocol/pubsub#get-pending"/> <feature var="google:jingleinfo"/> <feature var="jabber:iq:privacy"/> <feature var="urn:xmpp:archive:manage"/> <feature var="http://jabber.org/protocol/pubsub#subscription-options"/> <feature var="jabber:iq:last"/> <feature var="http://jabber.org/protocol/pubsub#create-and-configure"/> <feature var="urn:xmpp:ping"/> <feature var="http://jabber.org/protocol/pubsub#retrieve-items"/> <feature var="jabber:iq:time"/> <feature var="http://jabber.org/protocol/pubsub#create-nodes"/> <feature var="http://jabber.org/protocol/pubsub#persistent-items"/> <feature var="jabber:iq:version"/> <feature var="http://jabber.org/protocol/pubsub#presence-notifications"/> <feature var="http://jabber.org/protocol/pubsub"/> <feature var="http://jabber.org/protocol/pubsub#retrieve-affiliations"/> <feature var="http://jabber.org/protocol/pubsub#delete-nodes"/> <feature var="http://jabber.org/protocol/pubsub#purge-nodes"/> <feature var="http://jabber.org/protocol/disco#info"/> <feature var="http://jabber.org/protocol/rsm"/> </query> </iq>
1.2 查询某一项XMPP子域，如pubsub
<iq type='get' from='wangxin@im/PC' to='pubsub.im' id='11'> <query xmlns='http://jabber.org/protocol/disco#info'/> </iq>
返回：
<iq id="11" to="wangxin@im/PC" from="pubsub.im" type="result"> <query xmlns="http://jabber.org/protocol/disco#info"> <identity category="pubsub" name="Publish-Subscribe service" type="service"/> <feature var="http://jabber.org/protocol/pubsub"/> <feature var="http://jabber.org/protocol/pubsub#collections"/> <feature var="http://jabber.org/protocol/pubsub#config-node"/> <feature var="http://jabber.org/protocol/pubsub#create-and-configure"/> <feature var="http://jabber.org/protocol/pubsub#create-nodes"/> <feature var="http://jabber.org/protocol/pubsub#delete-nodes"/> <feature var="http://jabber.org/protocol/pubsub#get-pending"/> <feature var="http://jabber.org/protocol/pubsub#instant-nodes"/> <feature var="http://jabber.org/protocol/pubsub#item-ids"/> <feature var="http://jabber.org/protocol/pubsub#meta-data"/> <feature var="http://jabber.org/protocol/pubsub#modify-affiliations"/> <feature var="http://jabber.org/protocol/pubsub#manage-subscriptions"/> <feature var="http://jabber.org/protocol/pubsub#multi-subscribe"/> <feature var="http://jabber.org/protocol/pubsub#outcast-affiliation"/> <feature var="http://jabber.org/protocol/pubsub#persistent-items"/> <feature var="http://jabber.org/protocol/pubsub#presence-notifications"/> <feature var="http://jabber.org/protocol/pubsub#publish"/> <feature var="http://jabber.org/protocol/pubsub#publisher-affiliation"/> <feature var="http://jabber.org/protocol/pubsub#purge-nodes"/> <feature var="http://jabber.org/protocol/pubsub#retract-items"/> <feature var="http://jabber.org/protocol/pubsub#retrieve-affiliations"/> <feature var="http://jabber.org/protocol/pubsub#retrieve-default"/> <feature var="http://jabber.org/protocol/pubsub#retrieve-items"/> <feature var="http://jabber.org/protocol/pubsub#retrieve-subscriptions"/> <feature var="http://jabber.org/protocol/pubsub#subscribe"/> <feature var="http://jabber.org/protocol/pubsub#subscription-options"/> <feature var="http://jabber.org/protocol/pubsub#default_access_model_open"/> <feature var="http://jabber.org/protocol/disco#info"/> </query> </iq>
1.3 查询发布订阅中的某一个持久化的叶子节点
<iq type='get' from='wangxin@im/PC' to='pubsub.im' id='info1'> <query xmlns='http://jabber.org/protocol/disco#info' node='NodeID_003'/> </iq>
返回
<iq id="info1" to="wangxin@im/PC" from="pubsub.im" type="result"> <query xmlns="http://jabber.org/protocol/disco#info" node="NodeID_003"> <identity category="pubsub" name="null" type="leaf"/> <feature var="http://jabber.org/protocol/pubsub"/> <feature var="http://jabber.org/protocol/disco#info"/> <x xmlns="jabber:x:data" type="result"> <field var="FORM_TYPE" type="hidden"> <value>http://jabber.org/protocol/pubsub#meta-data</value> </field> <field label="节点的简化名" var="pubsub#title" type="text-single"> <value/> </field> <field label="节点的描述" var="pubsub#description" type="text-single"> <value/> </field> <field label="Whether the node is a leaf (default) or a collection" var="pubsub#node_type" type="text-single"> <value>leaf</value> </field> <field label="The collection with which a node is affiliated." var="pubsub#collection" type="text-single"/> <field label="是否允许订阅" var="pubsub#subscribe" type="boolean"> <value>1</value> </field> <field label="强制设置新的订阅" var="pubsub#subscription_required" type="boolean"> <value>0</value> </field> <field label="用事件通知投送有效载荷" var="pubsub#deliver_payloads" type="boolean"> <value>1</value> </field> <field label="当节点配置改变时通知订阅者" var="pubsub#notify_config" type="boolean"> <value>1</value> </field> <field label="当节点被删除时通知订阅者" var="pubsub#notify_delete" type="boolean"> <value>1</value> </field> <field label="当节点的项目被删除时通知订阅者" var="pubsub#notify_retract" type="boolean"> <value>1</value> </field> <field label="仅投送通知给有效的用户" var="pubsub#presence_based_delivery" type="boolean"> <value>0</value> </field> <field label="指定有效的数据类型给此节点" var="pubsub#type" type="text-single"> <value/> </field> <field label="XSLT信息体" var="pubsub#body_xslt" type="text-single"> <value/> </field> <field label="XSLT有效载荷" var="pubsub#dataform_xslt" type="text-single"> <value/> </field> <field label="指定谁可以订阅和查看项目" var="pubsub#access_model" type="list-single"> <value>open</value> <option> <value>authorize</value> </option> <option> <value>open</value> </option> <option> <value>presence</value> </option> <option> <value>roster</value> </option> <option> <value>whitelist</value> </option> </field> <field label="指定发布者模型" var="pubsub#publish_model" type="list-single"> <value>publishers</value> <option> <value>publishers</value> </option> <option> <value>subscribers</value> </option> <option> <value>open</value> </option> </field> <field label="好友列表允许订阅" var="pubsub#roster_groups_allowed" type="list-multi"/> <field label="有问题时联系相关人员" var="pubsub#contact" type="jid-multi"/> <field label="默认的语言" var="pubsub#language" type="text-single"> <value>English</value> </field> <field label="节点的主人" var="pubsub#owner" type="jid-multi"> <value>test17@im</value> </field> <field label="节点的发布者" var="pubsub#publisher" type="jid-multi"/> <field label="选择实体将收到的信息回复给项目" var="pubsub#itemreply" type="list-single"> <value>owner</value> </field> <field label="多用户对话房间的回复将被传递" var="pubsub#replyroom" type="jid-multi"/> <field label="给用户的回复将被传递" var="pubsub#replyto" type="jid-multi"/> <field label="发送项目给新的订阅者" var="pubsub#send_item_subscribe" type="boolean"> <value>1</value> </field> <field label="持续的项目被存储" var="pubsub#persist_items" type="boolean"> <value>0</value> </field> <field label="项目的最大数字被持续化" var="pubsub#max_items" type="text-single"> <value>-1</value> </field> <field label="最大的有效载荷字节大小" var="pubsub#max_payload_size" type="text-single"> <value>5120</value> </field> </x> </query> </iq>
测试：通过smackx 和spark im客户端实现发布订阅
发布者：
import java.util.Date; import org.jivesoftware.smack.XMPPConnection; import org.jivesoftware.smackx.pubsub.AccessModel; import org.jivesoftware.smackx.pubsub.ConfigureForm; import org.jivesoftware.smackx.pubsub.FormType; import org.jivesoftware.smackx.pubsub.LeafNode; import org.jivesoftware.smackx.pubsub.PayloadItem; import org.jivesoftware.smackx.pubsub.PubSubManager; import org.jivesoftware.smackx.pubsub.PublishModel; import org.jivesoftware.smackx.pubsub.SimplePayload; public class Publisher { private static XMPPConnection connection = new XMPPConnection("im.cvte.cn"); private static String USRE_NAME = "test17"; private static String PASSWORD = "password"; private static String nodeId = "NodeID_003"; static{ try { connection.connect(); connection.login(USRE_NAME,PASSWORD); } catch (Exception e) { e.printStackTrace(); } } public static void main(String[] args)throws Exception{ try{ PubSubManager manager = new PubSubManager(connection,"pubsub.im"); LeafNode myNode = null; try { myNode = manager.getNode(nodeId); //创建叶子节点 } catch (Exception e) { e.printStackTrace(); } if(myNode == null){ myNode = manager.createNode(nodeId); } String id1 = "1001"; SimplePayload payload1 = new SimplePayload("message","pubsub:cvtalk","<message xmlns='pubsub:cvtalk'><body>"+ id1+":消息发布:"+ new Date().toString()+"</body></message>" ); //设置叶子节点参数，目前失灵 ConfigureForm f = new ConfigureForm(FormType.submit); //配置参数 f.setPersistentItems(true); //是否持久化 f.setDeliverPayloads(true); f.setAccessModel(AccessModel.open); f.setPublishModel(PublishModel.publishers); //f.setSubscribe(true); //通过设置创建叶子 //myNode =(LeafNode)manager.createNode(nodeId, f); PayloadItem<SimplePayload> item1 = new PayloadItem<SimplePayload>(id1, payload1); //不带itemID的SimplePayload，同样是OK的 //PayloadItem<SimplePayload> item1 = new PayloadItem<SimplePayload>(payload1); myNode.publish(item1); System.out.println("-----publish item1-----------"); } catch(Exception E) {E.printStackTrace();} } }
订阅者，这里的代码请写到spark的LoginDialog的login()方法 ：
private boolean login() { ....... connection.login(....... .......
PubSubManager manager = new PubSubManager(connection,"pubsub.im"); Node eventNode = manager.getNode("NodeID_003"); eventNode.addItemEventListener(new ItemEventListener<PayloadItem>() { public void handlePublishedItems(ItemPublishEvent evt) { System.out.println("收到订阅的载荷数量=" + evt.getItems().size()); for (Object obj : evt.getItems()) { PayloadItem<SimplePayload> item = (PayloadItem<SimplePayload>) obj; System.out.println("订阅项目=" + item.getPayload().toString()); } } }); eventNode.subscribe(connection.getUser());
......
订阅到达的消息
<message id="NodeID_003__wangxin@im__0K463" to="wangxin@im/PC" from="pubsub.im"> <thread>n4Ch63</thread> <event xmlns="http://jabber.org/protocol/pubsub#event"> <items node="NodeID_003"> <item id="1001"> <message xmlns="pubsub:cvtalk"> <body>1001:消息发布:Tue Dec 08 15:36:59 CST 2015</body> </message> </item> </items> </event> <headers xmlns="http://jabber.org/protocol/shim"> <header name="pubsub#subid">GP00jOONb9Lg2PRr0K0T01xunpquPmVC2q7QhjYg</header> </headers> </message>
smack中的pubsub的其他操作
获取节点配置
public ConfigureForm getDefaultConfiguration() throws XMPPException { // Errors will cause exceptions in getReply, so it only returns // on success. PubSub reply = (PubSub)sendPubsubPacket(Type.GET, new NodeExtension(PubSubElementType.DEFAULT), PubSubElementType.DEFAULT.getNamespace()); return NodeUtils.getFormFromPacket(reply, PubSubElementType.DEFAULT); }
删除节点
public void deleteNode(String nodeId) throws XMPPException { sendPubsubPacket(Type.SET, new NodeExtension(PubSubElementType.DELETE, nodeId), PubSubElementType.DELETE.getNamespace()); nodeMap.remove(nodeId); }
监听器
一共有3个监听：
- ItemDeleteListener
- ItemEventListener
- NodeConfigListener
其中 ItemEventListener使用的是泛型参数，类型是 org.jivesoftware.smackx.pubsub.Item
public interface ItemEventListener <T extends Item> { /** * Called whenever an item is published to the node the listener * is registered with. * * @param items The publishing details. */ void handlePublishedItems(ItemPublishEvent<T> items); }
另外，Personal Event Publishing (XEP-163) 也是基于发布订阅，xmpp包体结构很类似，发布的代码：
PEPManager pepManager = new PEPManager(smackConnection); pepManager.addPEPListener(new PEPListener() { public void eventReceived(String inFrom, PEPEvent inEvent) { LOGGER.debug("Event received: " + inEvent); } }); PEPProvider pepProvider = new PEPProvider(); pepProvider.registerPEPParserExtension("http://jabber.org/protocol/tune", new TuneProvider()); ProviderManager.getInstance().addExtensionProvider("event", "http://jabber.org/protocol/pubsub#event", pepProvider); Tune tune = new Tune("jeff", "1", "CD", "My Title", "My Track"); pepManager.publish(tune);
接收的监听：
public interface PEPListener { /** * Called when PEP events are received as part of a presence subscribe or message filter. * * @param from the user that sent the entries. * @param event the event contained in the message. */ public void eventReceived(String from, PEPEvent event); }
最后一个问题，在openfire中叶子节点上的新项目持久化到哪里了？
PubSubPersistenceManager类中writePendingItems负责持久化到数据库
private static void writePendingItems(Connection con, LinkedListNode<RetryWrapper> addItem, boolean batch) throws SQLException
但每次发布却看不到数据库中的记录，可以在下面代码找到答案，原来都提交内存了
writePendingItems(Connection con, LinkedList<RetryWrapper> addList, LinkedList<PublishedItem> delList) 将数据库中的记录删除了
/** * Flush the cache(s) of items to be persisted (itemsToAdd) and deleted (itemsToDelete). * @param sendToCluster If true, delegate to cluster members, otherwise local only */ public static void flushPendingItems(boolean sendToCluster) { // forward to other cluster members and wait for response if (sendToCluster) { CacheFactory.doSynchronousClusterTask(new FlushTask(), false); } if (itemsToAdd.getFirst() == null && itemsToDelete.getFirst() == null) { return; // nothing to do for this cluster member } Connection con = null; boolean rollback = false; LinkedList<RetryWrapper> addList = null; LinkedList<PublishedItem> delList = null; // Swap pending items so we can parse and save the contents from this point in time // while not blocking new entries from being cached. synchronized(itemsPending) { addList = itemsToAdd; delList = itemsToDelete; itemsToAdd = new LinkedList<RetryWrapper>(); itemsToDelete = new LinkedList<PublishedItem>(); // Ensure pending items are available via the item read cache; // this allows the item(s) to be fetched by other request threads // while being written to the DB from this thread int copied = 0; for (String key : itemsPending.keySet()) { if (!itemCache.containsKey(key)) { itemCache.put(key, (((RetryWrapper)itemsPending.get(key).object)).get()); copied++; } } if (log.isDebugEnabled() && copied > 0) { log.debug("Added " + copied + " pending items to published item cache"); } itemsPending.clear(); } // Note that we now make multiple attempts to write cached items to the DB: // 1) insert all pending items in a single batch // 2) if the batch insert fails, retry by inserting each item separately // 3) if a given item cannot be written, return it to the pending write cache // By default step 3 will be tried once per item, but this can be configured // (or disabled) using the "xmpp.pubsub.item.retry" property. In the event of // a transaction rollback, items that could not be written to the database // will be returned to the pending item write cache. try { con = DbConnectionManager.getTransactionConnection(); writePendingItems(con, addList, delList); } catch (SQLException se) { log.error("Failed to flush pending items; initiating rollback", se); // return new items to the write cache LinkedListNode<RetryWrapper> node = addList.getLast(); while (node != null) { savePublishedItem(node.object); node.remove(); node = addList.getLast(); } rollback = true; } finally { DbConnectionManager.closeTransactionConnection(con, rollback); } }
参考网页：
http://xmpp.org/extensions/xep-0060.html
http://xmpp.org/extensions/xep-0163.html
https://community.igniterealtime.org/thread/38433
http://www.igniterealtime.org/support/articles/pubsub.jsp
http://blog.csdn.net/u011163195/article/details/17683741