转载： http://www.cnblogs.com/relucent/p/4341295.html

XMPP是一种基于标准通用标记语言的子集XML的协议，它继承了在XML环境中灵活的发展性。

Smack是一个开源的用 java 写的XMPP(jabber)客户端代码库

因为XMPP是XML，所以进行扩展十分方便。而Smack也提供了对Message扩展的支持。

Smack对Message扩展主要需要两个接口

org.jivesoftware.smack.packet.PacketExtension
org.jivesoftware.smack.provider.PacketExtensionProvider

假设我们需要扩展一个消息回执，需要在Message中定义一个Received节点：

package org.jivesoftware.smack.packet;

import org.jivesoftware.smack.packet.PacketExtension;
import org.jivesoftware.smack.util.StringUtils;

public class Received implements PacketExtension { public static final String NAME = "received"; public static final String NAME_SPACE = "urn:xmpp:receipts"; private String id = ""; private Integer status = 0; /** * @return the id */ public String getId() { return id; } /** * @param id the id to set */ public void setId(String id) { this.id = id; } /** * @return the status */ public Integer getStatus() { return status; } /** * @param status the status to set */ public void setStatus(Integer status) { this.status = status; } @Override public String getElementName() { return "received"; } @Override public String getNamespace() { return "urn:xmpp:receipts"; } @Override public String toXML() { StringBuilder buffer = new StringBuilder(); buffer.append("<received xmlns=\"urn:xmpp:receipts\"");
        buffer.append(" id=\"").append(StringUtils.escapeForXML(id)).append("\"");
        buffer.append(" status=\"").append(status).append("\"");
        buffer.append("/>");
        return buffer.toString();
    }
}

然后我们需要定义一个Received的解析器

package org.jivesoftware.smack.provider;

import org.jivesoftware.smack.packet.PacketExtension;
import org.jivesoftware.smack.packet.Received;
import org.xmlpull.v1.XmlPullParser;

public class ReceivedProvider implements PacketExtensionProvider { @Override public PacketExtension parseExtension(XmlPullParser parser) throws Exception { boolean done = false; Received received = new Received(); while (!done) { int eventType = parser.next(); String name = parser.getName();//XML Tab标签 if (eventType == XmlPullParser.START_TAG) { if (name.equals("id")) { received.setId(parser.nextText()); } if (name.equals("status")) { received.setStatus(Integer.parseInt(parser.nextText().trim())); } } if (eventType == XmlPullParser.END_TAG) { if (Received.NAME.equals(name)) { done = true; } } } return received; } }

我们在使用Smack的时候需要将扩展的Provider添加到ProviderManager

ProviderManager.getInstance().addExtensionProvider(Received.NAME,Received.NAME_SPACE,new ReceivedProvider());

XML的格式

<message id="CJq74-1" to="to" from="from"><received xmlns="urn:xmpp:receipts" id="CJq74-0" status="1"/></message>

我们可以这样获得received

Received received=(Received)message.getExtension(Received.NAME,Received.NAME_SPACE);