<html><head><META http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Creating PARs and Web Applications</title><meta content="DocBook XSL Stylesheets V1.76.0" name="generator"><link rel="home" href="index.html" title="Virgo Programmer Guide"><link rel="up" href="ch04.html" title="Chapter&nbsp;4.&nbsp;Developing Applications"><link rel="prev" href="ch04.html" title="Chapter&nbsp;4.&nbsp;Developing Applications"><link rel="next" href="ch04s03.html" title="Creating Plans"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table summary="Navigation header" width="100%"><tr><td align="left" width="20%"><a accesskey="p" href="ch04.html">Prev</a>&nbsp;</td><th align="center" width="60%">&nbsp;</th><td align="right" width="20%">&nbsp;<a accesskey="n" href="ch04s03.html">Next</a></td></tr></table><hr></div><div class="section" title="Creating PARs and Web Applications"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="developing-applications-packaging"></a>Creating PARs and Web Applications</h2></div></div></div><p>
			Virgo supports two OSGi-oriented ways of packaging applications: the PAR format 
			and application bundles (including web bundles). The VTS also supports three
			distinct WAR deployment and packaging formats: standard Java EE WAR, Shared Libraries WAR, Shared Services WAR.
		</p><p>
			Virgo also supports plans as a way to describe an application. This method is similar to a PAR 
			in that it encapsulates all the artifacts of an application as a single unit, but differs in that a plan simply 
			lists the bundles in an XML file rather than packaging all the bundles in a single JAR file.  The use of plans 
			offers additional benefits to using PARs; for this reason, we recommend their use.  For details, see 
			<a class="link" href="ch04s03.html" title="Creating Plans">Creating Plans</a>.
		</p><div class="section" title="PARs"><div class="titlepage"><div><div><h3 class="title"><a name="developing-applications-packaging-par"></a>PARs</h3></div></div></div><p>
				An OSGi application is packaged as a JAR file, with extension <code class="literal">.par</code>. A PAR artifact offers several benefits:
				</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">A PAR file has an application name, version, symbolic name, and description.</li><li class="listitem">The artifacts of a PAR file are scoped so that they cannot
						be shared accidentally by other applications. The scope forms a boundary for automatic
						propagation of load time weaving and bundle refresh.
						See <a class="link" href="ch04s03.html#developing-applications-plans-scoping" title="Plans and Scoping">Plans and Scoping</a> for more on scoping.
					</li><li class="listitem">Since a PAR is scoped, its artifacts have their exported packages imported by the
						synthetic context bundle which is used for thread context class loading. So,
						for example, hibernate will be able to load classes of any of the exported
						packages of the bundles in a PAR file using the thread context class loader.</li><li class="listitem">A PAR file is visible to management interfaces.</li><li class="listitem">A PAR file can be undeployed and redeployed as a unit.</li><li class="listitem">
						A PAR file is <span class="emphasis"><em>atomic</em></span> in that it ties together the lifecycle of its artifacts. If you start, stop, or uninstall 
						one of a PAR's artifacts, Virgo escalates the operation to the whole PAR file.
						So Virgo prevents artifacts of a PAR from being in inconsistent states.
						For example, if one artifact should fail to start, then Virgo stops all artifacts in the PAR.
					</li></ul></div><p>
				See <a class="link" href="ch04s03.html#developing-applications-plans-scoping" title="Plans and Scoping">Plans and Scoping</a> for more information on scoping.
			</p><p>
				A PAR includes one or more application bundles and its manifest specifies the following
				manifest headers:
				</p><div class="table"><a name="developing-applications-packaging-par-headers-table"></a><p class="title"><b>Table&nbsp;4.1.&nbsp;PAR file headers</b></p><div class="table-contents"><table summary="PAR file headers" border="1"><colgroup><col><col></colgroup><thead><tr><th>Header</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">Application-SymbolicName</code></td><td>Identifier for the application which, in combination with Application-Version, uniquely identifies an application</td></tr><tr><td><code class="literal">Application-Name</code></td><td>Human readable name of the application</td></tr><tr><td><code class="literal">Application-Version</code></td><td>Version of the application</td></tr><tr><td><code class="literal">Application-Description</code></td><td>Short description of the application</td></tr></tbody></table></div></div><p><br class="table-break">
			</p><p>
				The following code shows an example MANIFEST.MF in a PAR file:
			</p><pre class="programlisting"><span class="bold"><strong>Application-SymbolicName</strong></span>: com.example.shop
<span class="bold"><strong>Application-Version</strong></span>: 1.0
<span class="bold"><strong>Application-Name</strong></span>: Online Shop
<span class="bold"><strong>Application-Description</strong></span>: Example.com&rsquo;s Online Shopping Application</pre><p>
			</p></div><div class="section" title="Web Application Bundles"><div class="titlepage"><div><div><h3 class="title"><a name="developing-applications-web-application-bundles"></a>Web Application Bundles</h3></div></div></div><p>
				Virgo Server for Apache Tomcat supports Web Application Bundles that are compliant with the OSGi Web Applications specification. 
				The defining property of a Bundle that makes it a Web Application Bundle is a manifest header, <code class="literal">Web-ContextPath</code>. 
				This defines the context path the web application will be registered under. 
			</p><p>
				See <a class="link" href="ch04s05.html" title="Using Spring, Spring DM, and Blueprint">Using Spring and Spring DM</a> for information on using Spring or Spring DM in a Web Application Bundle.
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