title: Deploying an application without undeploying previous one and with no downtime?
body: <p>I use Glassfish Java, and JSP over MySQL for my web applications. Many online people uses this web application and that web-site should not be down. </p>
  
  <p>When I want to deploy a new war file, I should undeploy and deploy the new one for my application at server.</p>
  
  <p>My question is that;</p>
  
  <p><code>Is there any technology that doesn't need to undeploy my application and just change the appropriate classes so no need to redoploy it again?</code></p>