title: Java - Hot deployment
body: <p>Recently, I was reading book about Erlang which has hot deployment feature. The deployment can be done without bringing the system down. All the existing requests will be handled by old version of code and all the new request after deployment will be served by the new code. In these case, both the versions of code available in runtime for sometime till all the old requests are served. Is there any approach in Java where we can keep 2 versions of jar files? Is there any app/web servers support this?</p>