title: ClassNotFoundException/NoClassDefFoundError in my Java web application
body: <p>I developer a web application using Java. When I deploy it to my application server (Jetty, Tomcat, JBoss, GlassFish, etc.) throws an error. I can see this error message in the stacktrace:</p>
  
  <pre><code>java.lang.ClassNotFoundException
  </code></pre>
  
  <p>Or</p>
  
  <pre><code>java.lang.NoClassDefFoundError
  </code></pre>
  
  <p>What does this mean and how can I fix it?</p>