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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><!--NewPage--><HTML><HEAD><TITLE>DiscoveryService (Project JXTA J2SE)</TITLE><META NAME="keywords" CONTENT="net.jxta.discovery.DiscoveryService interface"><LINK REL ="stylesheet" TYPE="text/css" HREF="../../../stylesheet.css" TITLE="Style"><SCRIPT type="text/javascript">function windowTitle(){ parent.document.title="DiscoveryService (Project JXTA J2SE)";}</SCRIPT></HEAD><BODY BGCOLOR="white" onload="windowTitle();"><!-- ========= START OF TOP NAVBAR ======= --><A NAME="navbar_top"><!-- --></A><A HREF="#skip-navbar_top" title="Skip navigation links"></A><TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0" SUMMARY=""><TR><TD COLSPAN=3 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"><A NAME="navbar_top_firstrow"><!-- --></A><TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3" SUMMARY=""> <TR ALIGN="center" VALIGN="top"> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../overview-summary.html"><FONT CLASS="NavBarFont1"><B>Overview</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-summary.html"><FONT CLASS="NavBarFont1"><B>Package</B></FONT></A> </TD> <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> <FONT CLASS="NavBarFont1Rev"><B>Class</B></FONT> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="class-use/DiscoveryService.html"><FONT CLASS="NavBarFont1"><B>Use</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>Tree</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>Deprecated</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../index-all.html"><FONT CLASS="NavBarFont1"><B>Index</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../help-doc.html"><FONT CLASS="NavBarFont1"><B>Help</B></FONT></A> </TD> </TR></TABLE></TD><TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM><a href='http://www.jxta.org' target='_blank'>Project JXTA</a></EM></TD></TR><TR><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../../net/jxta/discovery/DiscoveryListener.html" title="interface in net.jxta.discovery"><B>PREV CLASS</B></A> NEXT CLASS</FONT></TD><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../../index.html" target="_top"><B>FRAMES</B></A> <A HREF="DiscoveryService.html" target="_top"><B>NO FRAMES</B></A> <SCRIPT type="text/javascript"> <!-- if(window==top) { document.writeln('<A HREF="../../../allclasses-noframe.html"><B>All Classes</B></A>'); } //--></SCRIPT><NOSCRIPT> <A HREF="../../../allclasses-noframe.html"><B>All Classes</B></A></NOSCRIPT></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2"> SUMMARY: NESTED | <A HREF="#field_summary">FIELD</A> | CONSTR | <A HREF="#method_summary">METHOD</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">DETAIL: <A HREF="#field_detail">FIELD</A> | CONSTR | <A HREF="#method_detail">METHOD</A></FONT></TD></TR></TABLE><A NAME="skip-navbar_top"></A><!-- ========= END OF TOP NAVBAR ========= --><HR><!-- ======== START OF CLASS DATA ======== --><H2><FONT SIZE="-1">net.jxta.discovery</FONT><BR>Interface DiscoveryService</H2><DL><DT><B>All Superinterfaces:</B> <DD><A HREF="../../../net/jxta/platform/Module.html" title="interface in net.jxta.platform">Module</A>, <A HREF="../../../net/jxta/service/Service.html" title="interface in net.jxta.service">Service</A></DD></DL><DL><DT><B>All Known Implementing Classes:</B> <DD><A HREF="../../../net/jxta/impl/discovery/DiscoveryServiceImpl.html" title="class in net.jxta.impl.discovery">DiscoveryServiceImpl</A>, <A HREF="../../../net/jxta/impl/discovery/DiscoveryServiceInterface.html" title="class in net.jxta.impl.discovery">DiscoveryServiceInterface</A></DD></DL><HR><DL><DT>public interface <B>DiscoveryService</B><DT>extends <A HREF="../../../net/jxta/service/Service.html" title="interface in net.jxta.service">Service</A></DL><P>The JXTA DiscoveryService provides an asynchronous mechanism for discovering Peer Advertisements, Group Advertisements, and other general JXTA Advertisements (pipe, service, etc.). The scope of discovery can be controlled by specifying name and attribute pair, and a threshold. The threshold is an upper limit the requesting peer specifies for responding peers not to exceed. Each JXTA Peer Group has an instance of a DiscoveryService. The scope of discovery is limited to the group. For example : <p/>A peer in the soccer group invokes the soccer group's DiscoveryService to discover pipe advertisements in the group, and is interested in a maximum of 10 Advertisements from each peer: <pre> discovery.getRemoteAdvertisements(null, discovery.ADV, null, null, 10, null); </pre> <p/>In the above example, peers that are part of the soccer group would respond. After a getRemoteAdvertisements call is made and the peers respond, a call to getLocalAdvertisements can be made to retrieve results that have been found and added to the local group cache. Alternately, a call to addDiscoveryListener() will provide asynchronous notification of discovered advertisements. <p/>Advertisement indexes are shared with a rendezvous peer upon connect, and subsequent publications are shared at 30 second intervals <p/>DiscoveryService also provides a mechanism for publishing advertisements, so that they may be discovered. The rules to follow when publishing are: <ul> <li> use the current discovery service to publish advertisements private to the group. <pre>discovery.publish(adv,discovery.ADV); </pre></li> <li>Use the parent's discovery to publish advertisements that public outside of the group. Example : a peer would like publish the "soccer" group in the NetPeerGroup <pre> parent=soccerGroup.getParent(); discovery= parent.getDiscoveryService() discovery.publish(adv,discovery.ADV); </pre></li> </ul> <p/>The threshold can be utilized in peer discovery in situations where a peer is only interested in other peers, and not about additional peers they may know about. To achieve this effect for peer discovery set the Threshold to <code>0</code> <p/>Advertisements are often stored in a persistant local cache. When a peer restarts up the same cache is referenced. this is an area where several optimizations can take place, and intelligence about discovery patterns, etc. <p/>Another feature of discovery is automatic discovery, a peer initiates a discovery message by including it's own Advertisement in the discovery message, which also can be viewed as a announcement. <p/>Another feature of discovery is a learning about other rendezvous, i.e. when discovery comes across a peer advertisement of a rendezvous peer it passes the information down to the endpoint router.<P><P><DL><DT><B>See Also:</B><DD><A HREF="../../../net/jxta/service/Service.html" title="interface in net.jxta.service"><CODE>Service</CODE></A>, <A HREF="../../../net/jxta/resolver/ResolverService.html" title="interface in net.jxta.resolver"><CODE>ResolverService</CODE></A>, <A HREF="../../../net/jxta/protocol/DiscoveryQueryMsg.html" title="class in net.jxta.protocol"><CODE>DiscoveryQueryMsg</CODE></A>, <A HREF="../../../net/jxta/protocol/DiscoveryResponseMsg.html" title="class in net.jxta.protocol"><CODE>DiscoveryResponseMsg</CODE></A>, <A HREF="../../../net/jxta/protocol/ResolverQueryMsg.html" title="class in net.jxta.protocol"><CODE>ResolverQueryMsg</CODE></A>, <A HREF="../../../net/jxta/protocol/ResolverResponseMsg.html" title="class in net.jxta.protocol"><CODE>ResolverResponseMsg</CODE></A></DL><HR><P><!-- ======== NESTED CLASS SUMMARY ======== --><!-- =========== FIELD SUMMARY =========== --><A NAME="field_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Field Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static int</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#ADV">ADV</A></B></CODE><BR> DiscoveryService type Advertisement</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static long</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#DEFAULT_EXPIRATION">DEFAULT_EXPIRATION</A></B></CODE><BR> Default expiration time for advertisements. </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static long</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#DEFAULT_LIFETIME">DEFAULT_LIFETIME</A></B></CODE><BR> Default lifetime time for advertisements. </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static int</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#GROUP">GROUP</A></B></CODE><BR> DiscoveryService type Group</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static long</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#INFINITE_LIFETIME">INFINITE_LIFETIME</A></B></CODE><BR> Infintite lifetime for advertisements. </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static long</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#NO_EXPIRATION">NO_EXPIRATION</A></B></CODE><BR> Specifies that the advertisment will have no expiration and will be kept indefinitly.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static int</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#PEER">PEER</A></B></CODE><BR> DiscoveryService type Peer</TD></TR></TABLE> <A NAME="fields_inherited_from_class_net.jxta.platform.Module"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor"><TD><B>Fields inherited from interface net.jxta.platform.<A HREF="../../../net/jxta/platform/Module.html" title="interface in net.jxta.platform">Module</A></B></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><A HREF="../../../net/jxta/platform/Module.html#START_AGAIN_PROGRESS">START_AGAIN_PROGRESS</A>, <A HREF="../../../net/jxta/platform/Module.html#START_AGAIN_STALLED">START_AGAIN_STALLED</A>, <A HREF="../../../net/jxta/platform/Module.html#START_OK">START_OK</A></CODE></TD></TR></TABLE> <!-- ======== CONSTRUCTOR SUMMARY ======== --><!-- ========== METHOD SUMMARY =========== --><A NAME="method_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Method Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> void</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#addDiscoveryListener(net.jxta.discovery.DiscoveryListener)">addDiscoveryListener</A></B>(<A HREF="../../../net/jxta/discovery/DiscoveryListener.html" title="interface in net.jxta.discovery">DiscoveryListener</A> listener)</CODE><BR> register a discovery listener, to notified on discovery events</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> void</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#flushAdvertisement(net.jxta.document.Advertisement)">flushAdvertisement</A></B>(<A HREF="../../../net/jxta/document/Advertisement.html" title="class in net.jxta.document">Advertisement</A> adv)</CODE><BR> flush a stored Advertisement</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> void</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#flushAdvertisements(java.lang.String, int)">flushAdvertisements</A></B>(java.lang.String id, int type)</CODE><BR> flushs stored Advertisement(s),</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> long</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#getAdvExpirationTime(net.jxta.document.Advertisement)">getAdvExpirationTime</A></B>(<A HREF="../../../net/jxta/document/Advertisement.html" title="class in net.jxta.document">Advertisement</A> adv)</CODE><BR> Returns the maximum duration in milliseconds for which this document should be cached by those other than the publisher. </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> long</CODE></FONT></TD><TD><CODE><B><A HREF="../../../net/jxta/discovery/DiscoveryService.html#getAdvExpirationTime(net.jxta.id.ID, int)">getAdvExpirationTime</A></B>(<A HREF="../../../net/jxta/id/ID.html" title="class in net.jxta.id">ID</A> id, int type)</CODE><BR> Returns the maximum duration in milliseconds for which this document should be cached by those other than the publisher. </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">⌨️ 快捷键说明
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