title: Dynamic Web Module 3.0 -- 3.1
body: <p>I have a mavenized codebased configured Spring 3.2.4 web app. 
  When I build the app with Maven/pom.xml first I got an error that web.xml is missing. 
  first I tried to create an empty web.xml. this was the moment when The project facets changed (and I don't know why). It switched from dynamic Web Module 3.0 to 3.1 and this is irreversible. 
  How can I change it again into Dynamic Web Modules 3.0??? </p>
  
  <p><img src="https://i.stack.imgur.com/4pmqT.png" alt="enter image description here"></p>
  
  <p>Additionally I can't remove the JAX-RS. Trying this it results in:</p>
  
  <pre><code>Failed while uninstalling JAX-RS (REST Web Services) 1.0.
  org.eclipse.jst.javaee.web.internal.impl.WebAppImpl cannot be cast to org.eclipse.jst.j2ee.webapplication.WebApp
  </code></pre>
  
  <p>Later I found out that I can avoid the Maven compile error by inserting the according plugin into pom.xml:</p>
  
  <pre><code>&lt;plugin&gt;
      &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
      &lt;artifactId&gt;maven-war-plugin&lt;/artifactId&gt;
      &lt;version&gt;2.4&lt;/version&gt;
      &lt;configuration&gt;
          &lt;failOnMissingWebXml&gt;false&lt;/failOnMissingWebXml&gt;
      &lt;/configuration&gt;
  &lt;/plugin&gt;
  </code></pre>