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38<H1><A name="TemporalServiceDependency-Thetemporaldependencyhandler"></A>The temporal dependency handler</H1>
39<P>Regular service dependencies participate to the instance lifecycle. Moreover, the injected service object is either available or not available. A temporal dependency handler is a little different and provides a different resolution pattern. Indeed, the temporal dependency does not invalidate the instance. Moreover, if not available, the temporal dependency waits (and so blocks the current thread) for a provider. Of course, the maximum waiting time can be specified. If a timeout occurs, the handler throws a runtime exception.</P>
40<H2><A name="TemporalServiceDependency-Usingthehandler"></A>Using the handler</H2>
41<P>First of all, you need to configure the component type to use the handler such as:</P>
42<DIV class="code"><DIV class="codeContent">
43<PRE class="code-xml"><SPAN class="code-tag">&lt;iPOJO <SPAN class="code-keyword">xmlns:temporal</SPAN>=<SPAN class="code-quote">&quot;org.apache.felix.ipojo.handler.temporal&quot;</SPAN>&gt;</SPAN>
44 &lt;component
45 className=<SPAN class="code-quote">&quot;org.apache.felix.ipojo.example.Temporal&quot;</SPAN>&gt;
46
47 <SPAN class="code-tag">&lt;!-&mdash;Temporal dependency configuration --&gt;</SPAN>
48 &lt;temporal:requires field=<SPAN class="code-quote">&quot;mytemporal&quot;</SPAN>
49 /&gt;
50 <SPAN class="code-tag">&lt;provides /&gt;</SPAN>
51 <SPAN class="code-tag">&lt;/component&gt;</SPAN>
52<SPAN class="code-tag">&lt;/iPOJO&gt;</SPAN></PRE>
53</DIV></DIV>
54<P>Notice that, this handler is an external handler. So, it uses the &quot;org.apache.felix.ipojo.handler.temporal&quot; namespace.<BR>
55Once described, you can implement your component. The specified field will be mapped to the temporal dependency. As for regular field injection, aggregation, targeted service specification (i.e. interface) are discovered automatically. Filter, comparator and binding policy are also supported. However, the optional attribute is not supported. In fact, this attribute is meaningless in the case of a temporal dependency.<BR>
56Using the field in your code will try to find a matching service provider. If a provider is available, the field receives the service object immediately. Else, the thread is stopped and waits for a provider. The default wait time is 3s (you can also specify this time). If no provider is available after this time, the thread throws a RuntimeException. If a provider becomes available during this time, the field receives immediately the value and the execution can continue.</P>
57<H2><A name="TemporalServiceDependency-Configuration"></A>Configuration</H2>
58<P>The handler has only one mandatory attributes:</P>
59<UL>
60 <LI>Field: the implementation field supporting the dependency</LI>
61</UL>
62
63
64<P>The handler supports on specific optional attributes:</P>
65<UL>
66 <LI>Timeout: the maximum time waited in order to find a provider (default: 3s)</LI>
67</UL>
68
69
70<P>The attribute form regular dependencies are also supported.</P>
71<H2><A name="TemporalServiceDependency-Download"></A>Download</H2>
72<P>The handler is available on the <A href="http://felix.apache.org/site/download.html" title="Download">download</A> page.<BR>
73Sources are available on the Felix trunk at the following location: <SPAN class="nobr"><A href="https://svn.apache.org/repos/asf/felix/trunk/ipojo/temporal.dependency.handler" title="Visit page outside Confluence" rel="nofollow">https://svn.apache.org/repos/asf/felix/trunk/ipojo/temporal.dependency.handler<SUP><IMG class="rendericon" src="http://cwiki.apache.org/confluence/images/icons/linkext7.gif" height="7" width="7" align="absmiddle" alt="" border="0"></SUP></A></SPAN></P></TD>
74<TD class="confluenceTd" valign="top" width="20%">
75<H6><A name="TemporalServiceDependency-Overview"></A><B>Overview</B></H6>
76<UL>
77 <LI><A href="http://felix.apache.org/site/apache-felix-ipojo.html" title="Apache Felix iPOJO">Home Page</A></LI>
78 <LI><A href="http://felix.apache.org/site/apache-felix-ipojo-feature-overview.html" title="Apache Felix iPOJO Feature Overview">iPOJO Feature Overview</A></LI>
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82
83<H6><A name="TemporalServiceDependency-GettingStarted"></A><B>Getting Started</B></H6>
84<UL>
85 <LI><A href="http://felix.apache.org/site/ipojo-in-10-minutes.html" title="iPOJO in 10 minutes">iPOJO in 10 minutes</A></LI>
86 <LI><A href="http://felix.apache.org/site/ipojo-hello-word-maven-based-tutorial.html" title="iPOJO Hello Word (Maven-Based) tutorial">iPOJO Hello Word &#40;Maven&#45;Based&#41; tutorial</A></LI>
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91<H6><A name="TemporalServiceDependency-UserGuide"></A><B>User Guide</B></H6>
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100<H6><A name="TemporalServiceDependency-Tools"></A><B>Tools</B></H6>
101<UL>
102 <LI><A href="http://felix.apache.org/site/ipojo-eclipse-plug-in.html" title="iPOJO Eclipse Plug-in">iPOJO Eclipse Plug&#45;in</A></LI>
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105 <LI><A href="http://felix.apache.org/site/ipojo-concepts-overview.html" title="iPOJO Concepts Overview">iPOJO concepts overview</A></LI>
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107
108
109<H6><A name="TemporalServiceDependency-DeveloperGuide"></A><B>Developer Guide</B></H6>
110<UL>
111 <LI><A href="http://felix.apache.org/site/how-to-write-your-own-handler.html" title="How to write your own handler">How to write your own handler</A></LI>
112 <LI><A href="http://felix.apache.org/site/how-to-use-ipojo-manipulation-metadata.html" title="How to use iPOJO Manipulation Metadata">How to use iPOJO Manipulation Metadata</A></LI>
113</UL>
114
115
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