开发创建XMPP“发布订阅”扩展（xmpp pubsub extend）

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：

 

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：

 

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