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<document>  <header>    <product>resin</product>    <title>A Resource with JCA Lifecycle</title>    <type>tutorial</type>    <description>      <p>      Resources can receive lifecycle events by implementing       javax.resource.spi.ResourceAdapter.      </p>    </description> <tutorial-startpage>demo.jsp</tutorial-startpage>  </header>  <body><summary/><s1 title="ResourceAdapter"><p>Many resources can take advantage of the lifecycle events providedby the Java Connector Architecture (JCA).  In Resin, any resourcewhich implements <code>javax.resource.spi.ResourceAdapter</code> will automaticallyreceive the JCA resource events and have access to the JCAcapabilities. Resources will generally want to implement the<code>start(ctx)</code> and <code>stop()</code> methods.</p><p>The <code>start</code> method is called when the environment isstarted.  In the case of a web-app, this will be before any servlet isinitialized, but after all the resources have been added to JNDI.</p><p>The <code>ctx</code> argument provides some capabilities includingtimers, and work management.  This demo will not use those capabilities.</p><p>The <code>stop</code> method is called when the environment closes,e.g. when the web-app is destroyed.</p><p>The complete lifecycle looks like the following:</p><ol><li>The environment is created (server, host, web-app, etc.)</li><li>The resources are created and configured:<ol><li><code>new test.TestResource()</code> is called from that environment</li><li>The configuration setters configure the resource (see <a href="config|init">Bean-style initialization</a>).</li><li>The <code>init()</code> method is called if available (part of Bean-style initialization)</li></ol></li><li>The resources are started<ol><li>The <code>start(ctx)</code> method is called for the ResourceAdapters</li></ol></li><li>The load-on-startup servlets start (for web-app only)</li><li>Requests are now allowed for the environment.</li><li>The environment starts shutting down (web-app, host, server)</li><li>The <code>stop()</code> method is called for any ResourceAdapters</li></ol><p>The <code>javax.resource.spi.ResourceAdapter</code> has a few moremethods which our resource does not need.  To avoid cluttering upthe example, our resource extends from<code>com.caucho.jca.AbstractResourceAdapter</code>, which providesstubs for those methods.</p><example title="TestResource.java">package test;import javax.resource.spi.BootstrapContext;import javax.resource.spi.ResourceAdapterInternalException;import com.caucho.jca.AbstractResourceAdapter;public class TestResource extends AbstractResourceAdapter {  private String _status = "new";  /**   * Called when the resource adapter starts.   */  public void start(BootstrapContext ctx)    throws ResourceAdapterInternalException  {    _status = "started";  }    /**   * Called when the resource adapter stops.   */  public void stop()    throws ResourceAdapterInternalException  {    _status = "stopped";  }  public String toString()  {    return "TestResource[" + _status + "]";  }}</example><p>The web.xml configuration is identical to any other resourceconfiguration.  Resin detects that <code>TestResource</code> hasimplemented <code>ResourceAdapter</code> and adds the capabilities.</p><example title="web.xml">&lt;web-app xmlns="http://caucho.com/ns/resin"&gt;  &lt;resource jndi-name="jca/test" type="test.TestResource"&gt;  &lt;/resource&gt;&lt;/web-app&gt;</example><p>The demonstration page is simple.  It just looks up the resource inJNDI and displays it.  Because the <code>toString()</code> methodcontains the <code>_status</code> value, we actuallysee something useful.</p><example title="demo.jsp">&lt;%@ page import='javax.naming.InitialContext' %&gt;&lt;%= new InitialContext().lookup("java:comp/env/jca/test") %&gt;</example><results>TestResult[started]</results></s1><s1 title="Compatibility"><p>Because the <code>ResourceAdapter</code> interface is part of theJCA spec, you can write ResourceAdapters in a portable manner.  So ifyou were forced to use another application server for some reason, youcould still use your architecture and your resource.  (Theconfiguration on the other app server would probably be morecumbersome and involve creating rar files and XML configuration, butthat's why you're using Resin.)</p></s1>  </body></document>
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