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<td width="100%"><h1>View Providers</h1></td>
<td align="right" valign="middle" nowrap><a href="Architecture.html" title="Backward to Understanding the Architecture of a Client Application"><img src="../../../images/backward.png" border="0"></a> <a href="../server/index.html" title="Forward to Dealing with Servers"><img src="../../../images/forward.png" border="0"></a></td>
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<p class="author">Author: Victor Roldan Betancort</p>
<p>
A <a href="../../../javadoc/org/eclipse/emf/cdo/view/CDOViewProvider.html" title="Interface in org.eclipse.emf.cdo.view"><code>view provider</code></a> allows clients to inject custom logic into the <a href="../../../javadoc/org/eclipse/emf/cdo/eresource/CDOResourceFactory.html" title="Interface in org.eclipse.emf.cdo.eresource"><code>resource factory</code></a> mechansim, capable of handling the whole <a href="../../../javadoc/org/eclipse/emf/cdo/session/CDOSession.html" title="Interface in org.eclipse.emf.cdo.session"><code>session</code></a> and <a href="../../../javadoc/org/eclipse/emf/cdo/view/CDOView.html" title="Interface in org.eclipse.emf.cdo.view"><code>view</code></a>
instantiation process. This permits to obtain <a href="http://download.eclipse.org/modeling/emf/emf/javadoc/2.7.0/org/eclipse/emf/ecore/resource/Resource.html" title="Interface in org.eclipse.emf.ecore.resource"><code>resources</code></a> through the <a href="http://download.eclipse.org/modeling/emf/emf/javadoc/2.7.0/org/eclipse/emf/ecore/resource/ResourceSet.html" title="Interface in org.eclipse.emf.ecore.resource"><code>resource set</code></a>
API transparently, without any prior CDO client API code. The view provider automatically kicks in the middle of the
<a href="http://download.eclipse.org/modeling/emf/emf/javadoc/2.7.0/org/eclipse/emf/ecore/resource/ResourceSet.html" title="Interface in org.eclipse.emf.ecore.resource"><code>ResourceSet.getResource()</code></a> call, forgetting
about the whole openning session / openning transaction process, which happens behind the scenes.
<p>
This is quite useful when integrating CDO with EMF-based frameworks and tools that are not prepared for a CDO
scenario themselves.
<p>
<b>Table of Contents</b> <p>
<table border="0">
<tr><td>1 </td><td colspan="3"><a href="ViewProviders.html#ProviderImplementation" title="Chapter in CDO Model Repository Documentation">Implementing a View Provider</a></td></tr>
<tr><td>2 </td><td colspan="3"><a href="ViewProviders.html#ContributeProviderProgrammatically" title="Chapter in CDO Model Repository Documentation">Contributing View Providers Programmatically</a></td></tr>
<tr><td>3 </td><td colspan="3"><a href="ViewProviders.html#ContributeProviderUsingExtensionPoint" title="Chapter in CDO Model Repository Documentation">Contributing View Providers Using Extension Points</a></td></tr>
</table>
</p>
<h2><a name="ProviderImplementation"></a>1 Implementing a View Provider</h2>
<p>
Clients should implement the <a href="../../../javadoc/org/eclipse/emf/cdo/view/CDOViewProvider.html" title="Interface in org.eclipse.emf.cdo.view"><code>CDOViewProvider</code></a> interface, or sub class the <a href="../../../javadoc/org/eclipse/emf/cdo/view/AbstractCDOViewProvider.html" title="Class in org.eclipse.emf.cdo.view"><code>AbstractCDOViewProvider</code></a>
class, which provides common functionality.
<p>
The example below shows a simple implementation that opens a <b>new</b> <a href="../../../javadoc/org/eclipse/emf/cdo/session/CDOSession.html" title="Interface in org.eclipse.emf.cdo.session"><code>session</code></a> to a local
server and a <b>new</b> <a href="../../../javadoc/org/eclipse/emf/cdo/transaction/CDOTransaction.html" title="Interface in org.eclipse.emf.cdo.transaction"><code>transaction</code></a> on that session.
<p>
<div class="snippet" style="margin-left:24px;" align="left">
<a name="snippet_example"></a>
<table border="0" cellspacing="0" cellpadding="0">
<tr>
<td><img src="../../../images/editor-top-left-java.png"></td>
<td style="background-image:url(../../../images/editor-top1.png); background-repeat:repeat-x;" width="1px"><font face="Segoe UI,Arial" size="-1">ExampleViewProvider.java</font></td>
<td width="1px"><img src="../../../images/editor-close.png"></td>
<td style="background-image:url(../../../images/editor-top2.png); background-repeat:repeat-x;"> </td>
<td><img src="../../../images/editor-top-right.png"></td>
</tr>
<tr>
<td style="background-image:url(../../../images/editor-left.png); background-repeat:repeat-y;"> </td>
<td colspan="3" align="left" valign="top" nowrap>
<div style="margin:10px 0px 10px 0px;">
<code>
<a name="callout_example_1_code" href="#callout_example_1" alt="The example provider catches all URIs with shape "cdo.local:"." title="The example provider catches all URIs with shape "cdo.local:"."><img src="../../../images/callout-1.png" width="16" height="16" border="0" align="top"></a> <font color="#7f0055"><b>new </b></font>AbstractCDOViewProvider(<font color="#2a00ff">"cdo\\.local:.*"</font>, <font color="#990000">100</font>)<br/>
{<br/>
<font color="#7f0055"><b>private </b></font>IManagedContainer container;<br/>
<br/>
<a name="callout_example_2_code" href="#callout_example_2" alt="Register the provider with CDOViewProviderRegistry." title="Register the provider with CDOViewProviderRegistry."><img src="../../../images/callout-2.png" width="16" height="16" border="0" align="top"></a> <font color="#7f0055"><b>public </b></font>CDOView getView(URI uri, ResourceSet resourceSet)<br/>
{<br/>
<font color="#7f0055"><b>if </b></font>(container == <font color="#7f0055"><b>null</b></font>)<br/>
{<br/>
container = <font color="#7f0055"><b>new </b></font>ManagedContainer();<br/>
Net4jUtil.prepareContainer(container);<br/>
TCPUtil.prepareContainer(container);<br/>
container.activate();<br/>
}<br/>
<br/>
<font color="#7f0055"><b>int </b></font>startIndex = uri.toString().indexOf(<font color="#990000">':'</font>);<br/>
String repoName = uri.toString().substring(startIndex);<br/>
<br/>
IConnector connector = (IConnector)container.getElement(<font color="#2a00ff">"org.eclipse.net4j.connectors"</font>, <font color="#2a00ff">"tcp"</font>, <font color="#2a00ff">"localhost"</font>);<br/>
<br/>
CDONet4jSessionConfiguration config = CDONet4jUtil.createNet4jSessionConfiguration();<br/>
config.setConnector(connector);<br/>
config.setRepositoryName(repoName);<br/>
<br/>
CDOSession session = config.openNet4jSession();<br/>
<font color="#7f0055"><b>return </b></font>session.openTransaction();<br/>
}<br/>
};
</code>
</div>
</td>
<td style="background-image:url(../../../images/editor-right.png); background-repeat:repeat-y;"> </td>
</tr>
<tr>
<td><img src="../../../images/editor-bottom-left.png"></td>
<td style="background-image:url(../../../images/editor-bottom.png); background-repeat:repeat-x;" colspan="3"> </td>
<td><img src="../../../images/editor-bottom-right.png"></td>
</tr>
</table>
</div>
<p>
<div style="margin-left:24px;"><a name="callout_example_1" href="#callout_example_1_code" alt="Jump to snippet..." title="Jump to snippet..."><img src="../../../images/callout-1.png" width="16" height="16" border="0" align="top"></a> The example provider catches all URIs with shape "cdo.local:<repoName>".
</div>
<div style="margin-left:24px;"><a name="callout_example_2" href="#callout_example_2_code" alt="Jump to snippet..." title="Jump to snippet..."><img src="../../../images/callout-2.png" width="16" height="16" border="0" align="top"></a> Register the provider with <a href="../../../javadoc/org/eclipse/emf/cdo/view/CDOViewProviderRegistry.html" title="Interface in org.eclipse.emf.cdo.view"><code>CDOViewProviderRegistry</code></a>.
</div>
<p>
<h2><a name="ContributeProviderProgrammatically"></a>2 Contributing View Providers Programmatically</h2>
<p>
A client's view provider implementation can be contributed programmatically to the <a href="../../../javadoc/org/eclipse/emf/cdo/view/CDOViewProviderRegistry.html" title="Interface in org.eclipse.emf.cdo.view"><code>CDOViewProviderRegistry</code></a>,
as the following example suggests:
<p>
<div class="snippet" style="margin-left:24px;" align="left">
<a name="snippet_snippet2"></a>
<table border="0" cellspacing="0" cellpadding="0">
<tr>
<td><img src="../../../images/editor-top-left-java.png"></td>
<td style="background-image:url(../../../images/editor-top1.png); background-repeat:repeat-x;" width="1px"><font face="Segoe UI,Arial" size="-1">ProviderContribution.java</font></td>
<td width="1px"><img src="../../../images/editor-close.png"></td>
<td style="background-image:url(../../../images/editor-top2.png); background-repeat:repeat-x;"> </td>
<td><img src="../../../images/editor-top-right.png"></td>
</tr>
<tr>
<td style="background-image:url(../../../images/editor-left.png); background-repeat:repeat-y;"> </td>
<td colspan="3" align="left" valign="top" nowrap>
<div style="margin:10px 0px 10px 0px;">
<code>
<font color="#3f7f5f">// Instantiate your view provider</font><br/>
CDOViewProvider viewProvider = <a name="callout_snippet2_1_code" href="#callout_snippet2_1" alt="Get the target CDOViewProvider implementation." title="Get the target CDOViewProvider implementation."><img src="../../../images/callout-1.png" width="16" height="16" border="0" align="top"></a> org.eclipse.emf.internal.cdo.view.PluginContainerViewProvider.INSTANCE;<br/>
<br/>
<font color="#3f7f5f">// Add the instance to the registry</font><br/>
<a name="callout_snippet2_2_code" href="#callout_snippet2_2" alt="Add the provider instance to CDOViewProviderRegistry." title="Add the provider instance to CDOViewProviderRegistry."><img src="../../../images/callout-2.png" width="16" height="16" border="0" align="top"></a> CDOViewProviderRegistry.INSTANCE.addViewProvider(viewProvider);
</code>
</div>
</td>
<td style="background-image:url(../../../images/editor-right.png); background-repeat:repeat-y;"> </td>
</tr>
<tr>
<td><img src="../../../images/editor-bottom-left.png"></td>
<td style="background-image:url(../../../images/editor-bottom.png); background-repeat:repeat-x;" colspan="3"> </td>
<td><img src="../../../images/editor-bottom-right.png"></td>
</tr>
</table>
</div>
<p>
<div style="margin-left:24px;"><a name="callout_snippet2_1" href="#callout_snippet2_1_code" alt="Jump to snippet..." title="Jump to snippet..."><img src="../../../images/callout-1.png" width="16" height="16" border="0" align="top"></a> Get the target <a href="../../../javadoc/org/eclipse/emf/cdo/view/CDOViewProvider.html" title="Interface in org.eclipse.emf.cdo.view"><code>CDOViewProvider</code></a> implementation.
</div>
<div style="margin-left:24px;"><a name="callout_snippet2_2" href="#callout_snippet2_2_code" alt="Jump to snippet..." title="Jump to snippet..."><img src="../../../images/callout-2.png" width="16" height="16" border="0" align="top"></a> Add the provider instance to <a href="../../../javadoc/org/eclipse/emf/cdo/view/CDOViewProviderRegistry.html" title="Interface in org.eclipse.emf.cdo.view"><code>CDOViewProviderRegistry</code></a>.
</div>
<p>
<h2><a name="ContributeProviderUsingExtensionPoint"></a>3 Contributing View Providers Using Extension Points</h2>
<p>
A specific <a href="../../../javadoc/org/eclipse/emf/cdo/view/CDOViewProvider.html" title="Interface in org.eclipse.emf.cdo.view"><code>CDOViewProvider</code></a> implementation can also be contributed using the
<code>org.eclipse.emf.cdo.viewProviders</code> extension point. Clients specify:
<p>
<ul>
<li>A mandatory <b><code>class</code></b> implementing the <a href="../../../javadoc/org/eclipse/emf/cdo/view/CDOViewProvider.html" title="Interface in org.eclipse.emf.cdo.view"><code>CDOViewProvider</code></a> interface.
<li>A mandatory <b>regular expression</b> string indicating the shape of <a href="http://download.eclipse.org/modeling/emf/emf/javadoc/2.7.0/org/eclipse/emf/common/util/URI.html" title="Class in org.eclipse.emf.common.util"><code>URIs</code></a> that should match with the contributed provider.
<li>An optional <b><code>priority</code></b> integer value, to indicate preference over other implementations
matching the same regular expression. A higher value indicates a higher priority, <a href="http://download.oracle.com/javase/1.5.0/docs/api/java/lang/Integer.html" title="Class in java.lang"><code>Integer#MAX_VALUE</code></a> being
the maximum priority value and <a href="http://download.oracle.com/javase/1.5.0/docs/api/java/lang/Integer.html" title="Class in java.lang"><code>Integer#MIN_VALUE</code></a> the minimum.
</ul>
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<a href="Architecture.html" title="Backward to Understanding the Architecture of a Client Application"><img src="../../../images/backward.png" border="0"></a> <a href="../server/index.html" title="Forward to Dealing with Servers"><img src="../../../images/forward.png" border="0"></a></p>
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<i>Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.</i>
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