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：

<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 = ;
            for (String key : itemsPending.keySet()) {
                if (!itemCache.containsKey(key)) {
                    itemCache.put(key, (((RetryWrapper)itemsPending.get(key).object)).get());
                    copied++;
                }
            }
            if (log.isDebugEnabled() && copied > ) {
                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