java - Difference between Deployment Assembly and J2EE Module Dependencies in Eclipse

Question

When using a Eclipse 3.7 Indigo for Java EE Developers, there is something called Deployment Assembly . I could find on google and understood that it is similar to the J2EE Module dependencies where in we could select the jar and which goes and sits in the EAR folder or in WEB-INF/lib in case of WAR. Now the doubt I have is,

I have a JavaProject Dependencies. I have added all the dependent Jars via classpath variable. Now the Dependencies Project is added as dependency to my Web Project TestWebProject. The compilation of the Web Project is correct but during runtime I get an error because some jar was not found. I could fix this my include jar in Deployment Assembly of Dependencies Project, which is a standalone project.

The question is that, why I had to fix the jar in deployment assembly since ,first, its a standalone project and second is if I would not have this deployment assembly , how could this be fixed?

Answer 1

I could find on google and understood that it is similar to the J2EE Module dependencies

It was called "J2EE Module Dependencies" until with Eclipse 3.5. After that version, it was renamed to "Deployment Assembly". But it's effectively the same in case of Java EE web projects.

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The question is that, why I had to fix the jar in deployment assembly since its a standalone project

Because this way Eclipse will autobuild a JAR file of the project and put in /WEB-INF/lib of the web project's deployment. If you don't do that, the JAR isn't available during webapp's runtime, but only during compiletime and Eclipse expects that you've already built and placed it anywhere else in runtime classpath, e.g. server's own /lib.

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if I would not have this deployment assembly , how could this be fixed?

Manually build/export the JAR and drop in webapp's own /WEB-INF/lib or server's own /lib. The "Deployment Assembly" configuration is however more easy and the recommended way.

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