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<document>  <header>    <product>resin</product>    <title>A Simple Resource Bean</title>    <type>tutorial</type>    <description>      <p>      Resources are beans configured in the resin.conf or resin-web.xml and      stored in the WebBeans registry.  The tutorial shows the configuration      of a trivial bean as a resource and using it from a JSP file.      </p>      </description> <tutorial-startpage>index.jsp</tutorial-startpage></header>  <body><localtoc/><s1 title="Overview"><p>A resource in Resin is any bean configured in theresin.conf or resin-web.xml.  Resources are stored in the WebBeans registry.Because resources can be any Java class conforming to the bean configurationpatterns, resources provide a flexible configuration.</p><p>There is also more documentationfor <a href="../../doc/resin-ioc.xtp">Resin's IoC/DependencyInjection</a>.</p><p>Some typical resources include:</p><ul><li>Databases</li><li>JMS connections</li><li>EJB stateful and stateless session beans</li><li>JCA resources</li></ul><p>Because resources are configured in the resin.conf/resin-web.xml and arecreated before any servlets start, they are very convenient for globallyavailable beans, even allowing for more complex configuration beans extendingthe idea of &lt;env-entry&gt; (which stored simple Strings orIntegers in JNDI.)</p></s1><s1 title="The TestResource bean"><p>The <code>TestResource</code> bean is almost as simple as possible.It has a single String configuration parameter and does nothing butprint its value using <code>toString()</code>.</p><example title="TestResource.java">package test;public class TestResource {  private String _value = "default";  public void setValue(String value)  {    _value = value;  }  public String toString()  {    return "TestResource[" + _value + "]";  }}</example><p>In other words, you have lots of flexibility of things to configureas resources.</p></s1><s1 title="resin-web.xml configuration"><p>The resin-web.xml (or resin.conf) configures the resource with the&lt;bean&gt; tag.  The resource is created and stored in theenvironment where it is defined.  So a resource configured in the&lt;host&gt; will be available for all web-apps in that host and aresource configured in a &lt;web-app&gt; will only be available for that&lt;web-app&gt;.</p><example title="resin-web.xml">&lt;web-app xmlns="http://caucho.com/ns/resin"&gt;  &lt;bean class="test.TestResource"&gt;    &lt;init&gt;      &lt;value&gt;An Example Resource&lt;/value&gt;    &lt;/init&gt;  &lt;/bean&gt;&lt;/web-app&gt;</example><deftable><tr> <th>tag</th>  <th>description</th></tr><tr>  <td>bean</td>  <td>defines the singleton service</td></tr><tr>  <td>class</td>  <td>the class name of the resource bean</td></tr><tr>  <td>init</td>  <td>Any bean-style configuration goes here</td></tr><tr>  <td>name</td>  <td>the optional WebBeans name of the resource</td></tr><tr>  <td>value</td>  <td>The example bean's <code>setValue</code> parameter.</td></tr></deftable></s1><s1 title="Using the resource from PHP"><p>Your PHP scripts can use any WebBeans resource by using the<code>java_bean()</code> method.  The method will return the namedresource.</p><example title="test.php">&lt;php?$resource = java_bean("testResource");echo "PHP resource: " . $resource . "\n";?></example></s1><s1 title="Using the resource from JSP"><p>JSP pages can also use WebBeans resource in the JSP expressionlanguage.</p><example title="test.jsp">JSP resource: ${testResource}</example></s1><s1 title="Using the resource from a Servlet"><p>The example uses a servlet to demonstrate the resource, but anyinjectable class could use <code>@In</code> to look up and use theresource.  Because resources are stored globally in WebBeans, they canavoid the complexity of passing objects around or storing in theservlet context.</p><p>If you save the resource, it's important that the saved field is reloadedwhen the web-app restarts.  The resource has thesame lifetime as its environment: web-app, host or cluster.  When thatenvironment closes, the resource is no longer valid and must be discarded.In particular, it is important to store any resource in an object's field,<b>not</b> in a static field or static hashtable.</p><example title="TestServlet.java">package test;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.webbeans.In;public class TestServlet extends HttpServlet {  @In private TestResource _resource;    public void doGet(HttpServletRequest req, HttpServletResponse res)    throws ServletException, IOException  {    PrintWriter out = res.getWriter();    out.println("Resource: " + _resource);  }}</example><results>Resource: TestResource[An example resource]</results></s1>  </body></document>
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