WAR vs EAR for web application with no EJB?

Question

I have a JEE web application that does not make use of EJBs. I am targeting Jetty/Tomcat for deployment some of the time and thus need a WAR packaging. However, I am also target JBoss and Websphere some of the time.

My understanding is that full-blown JEE application servers can take either EAR or WAR formats. When would I use one over the other and why? I understand they are both standard compressed file formats and I have read 10 different snippets that try to explain them (including this one), but am no closer to understanding the pros and cons of each.

Answer 1

If you have only web modules - use WAR file. If you have different J2EE modules - use EAR. Though you can deliver only web modules in EAR - there is no point in doing this (and you will need to do more complex deployment configuration)

Answer 2

The crucial point is if you need anything provided in an EAR file (which may contain said WAR file). If so, then it makes sense to deploy as an EAR.

It can also wire up some of the configuration you need to do manually in Tomcat etc. A typical example is the URL bound to the web application, where you need to override the default heuristic with a container specific configuration file for a WAR, but you can put it directly in the EAR configuration file.

Also, during development WARs can frequently be hotdeployed directly in exploded form, where EARs must be unpacked and deployed. For Glassfish from Eclipse the difference is quite noticeable.