title: How to use GWT - RPC to Tomcat server
body: <ol>
  <li>Installed Tomcat 6</li>
  <li>Installed Eclipse + GWT plugin</li>
  <li>Created GWT project with sample
  generated code</li>
  <li>Compliled GWT project (GWT compile)</li>
  <li>Copied war (compiled) directory from
  eclipse's workspace to TOMCAT
  webapps/ROOT folder</li>
  <li>Run localhost:8080 at my browser</li>
  </ol>
  
  <p>The sample.html page from the GWT project displays correct but when i try to make a server call an error occurs.</p>
  
  <ul>
  <li>No problem with jetty
  (Eclipse GWT develpment mode) - rpc
  work's fine</li>
  <li>PROBLEM at TOMCAT.</li>
  </ul>
  
  <p>The catalina.out log at TOMCAT says:</p>
  
  <blockquote>
    <p>Error deploying web application
    directory ROOT
    java.lang.UnsupportedClassVersionError:
    Bad version number in .class file
    (unable to load class
    com.tomcat.server.GreetingServiceImpl)</p>
  </blockquote>
  
  <p>I guess there might be a problem at WEB_INF/web.xml at servlet definition, here's my web.xml</p>
  
  <pre><code>&lt;web-app xmlns="http://java.sun.com/xml/ns/javaee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
     version="2.5"&gt;
  
    &lt;display-name&gt;Welcome to Tomcat&lt;/display-name&gt;
    &lt;description&gt;
       Welcome to Tomcat
    &lt;/description&gt;
  
    &lt;!-- Servlets --&gt;
    &lt;servlet&gt;
      &lt;servlet-name&gt;greetServlet&lt;/servlet-name&gt;
      &lt;servlet-class&gt;com.tomcat.server.GreetingServiceImpl&lt;/servlet-class&gt;
    &lt;/servlet&gt;
  
    &lt;servlet-mapping&gt;
      &lt;servlet-name&gt;greetServlet&lt;/servlet-name&gt;
      &lt;url-pattern&gt;/tomcat/greet&lt;/url-pattern&gt;
    &lt;/servlet-mapping&gt;
  
    &lt;!-- Default page to serve --&gt;
    &lt;welcome-file-list&gt;
      &lt;welcome-file&gt;Tomcat.html&lt;/welcome-file&gt;
    &lt;/welcome-file-list&gt;
  
  &lt;/web-app&gt;
  </code></pre>