catalogexchangequery.java

基于jxta的文件共享和聊天系统源代码,下载下来分析吧

/*
 * Created on 27-nov-2005
 *
 */
/**
 * @author magowiz
 *
 */
package catalog_exchange;

import java.io.InputStream;
import java.io.StringWriter;
import java.net.URL;
import java.util.Date;
import java.util.Enumeration;

import net.jxta.document.Document;
import net.jxta.document.Element;
import net.jxta.document.MimeMediaType;
import net.jxta.document.StructuredDocument;
import net.jxta.document.StructuredDocumentFactory;
import net.jxta.document.StructuredTextDocument;
import net.jxta.document.TextElement;

/**
 * Object that implements a Catalog Exchange Query, a XML JXTA Message that
 * will be sent by a peer who wants to download from another a catalog. 
 * */

public class CatalogExchangeQuery {
	
	
	private Date dateLastUpdate; /**The date of the last update of the owned catalog, if present*/
	private URL catalogUrl;/**The url from which the catalog can be downloaded*/
	private String catalogName;	/**The name of the catalog, identifies the catalog*/
	
	/**
     * Returns the last update date of the catalog if the querying peer
     * has got one. 
     */	
	public long getDateUpdate()
	{
	 long n=-1;
	 if (dateLastUpdate!=null)
	 	n=dateLastUpdate.getTime(); 
	 return n;
	}
	
	/**
     * Returns the url of the catalog.
     */	
	public URL getCatalogUrl()
	{
	 return catalogUrl;
	}
	
	/**
     * Catalog Name getter
     * 
     * @return Returns the name of the catalog.
     */
	public String getCatalogName()
	{
	 return catalogName;
	}
	
	/**
     * Empty constructor, doesn't do anything.
     * @deprecated
     */
	public CatalogExchangeQuery()
	{
	}
	
	
	/**
     * Constructor needed if a peer has got the catalog and wants to check
     * if any other peer has got a newer version.
     * @param cn the name of the catalog
     * @param curl the url which the catalog can be downloaded from
     * @param du the date of the last update of local catalog, in long format(milliseconds)
     */
	public CatalogExchangeQuery(String cn,URL curl,long du)
	{
		catalogName=cn;
		dateLastUpdate=new Date(du);
		catalogUrl=curl;
		
	}
	
	/**
     * Constructor needed if a peer hasn't got the catalog and wants to download
     * it from another peer.
     * @param cn the name of the catalog
     * @param curl the url which the catalog can be downloaded from
     */
	public CatalogExchangeQuery(String cn,URL curl)
	{
		catalogName=cn;
		catalogUrl=curl;
		dateLastUpdate=null;
	}
	
	/**
     * Method that creates and return the xml document which represents
     * the query.
     * @param asMimeType MimeType of the output document.
     * @return The query in xml document format.
     */
	public Document getDocument(MimeMediaType asMimeType)  	
	  {
		 StructuredDocument document = (StructuredTextDocument) 
	          StructuredDocumentFactory.newStructuredDocument(
	              asMimeType, "example:ExampleQuery");
	      Element element;
	      element = document.createElement("catalogName",catalogName);
	      document.appendChild(element);
	  	  element=document.createElement("catalogUrl",catalogUrl.toString());
	      document.appendChild(element);	
	      if(dateLastUpdate!=null)
	      	{element=document.createElement("dateLastUpdate",String.valueOf(dateLastUpdate.getTime()));
	  	  	document.appendChild(element);}
	      return document;
	  }

	/**
     * Constructor needed for the peer who receive the query to easily extract
     * info from query.
     * @param stream is the query xml document received
     */
	public CatalogExchangeQuery (InputStream stream) 
	 {
		StructuredTextDocument document=null;
	    try{ 
		 document = (StructuredTextDocument) 
	         StructuredDocumentFactory.newStructuredDocument(
	             new MimeMediaType("text/xml"), stream);
	    }
	    catch(Exception e){e.printStackTrace();}

	     Enumeration elements = document.getChildren();
	     
	     elements = document.getChildren();
	     while (elements.hasMoreElements())
	     {
	        
	         Element el = (Element) elements.nextElement();
	         TextElement element = (TextElement) el;
	         if(element.getName().equals("catalogName"))
	         {
	             catalogName = element.getTextValue();
	             continue;
	         }
	         if(element.getName().equals("catalogUrl"))
	         {
	             try{catalogUrl = new URL (element.getTextValue());}
	             catch (Exception e){e.printStackTrace();}
	             continue;
	         }
	         if(element.getName().equals("dateLastUpdate"))
	         {
	         	 long t=Long.valueOf(element.getTextValue()).longValue();
	             dateLastUpdate = new Date(t);
	             continue;
	         }
	         
	         
	         
	     } 
	     
	 }
	 
	
	/**
     * Method that returns the xml query document as String.
     * @return String rapresentation of the query.
     */
	 public String toString()
	 {
	     try
	     {
	         StringWriter out = new StringWriter();
	         StructuredTextDocument doc = 
	             (StructuredTextDocument) getDocument(
	                 new MimeMediaType("text/xml"));
	         doc.sendToWriter(out);

	         return out.toString();
	     }
	     catch (Exception e)
	     {
	        e.printStackTrace(); 
	     	return "";
	     }
	 }
	

}