You can run your application in eclipse as normal java application. Create a project with all depnedencies and then you can use simply use ANT to target main class and invoke it with all other arguments and ussual settings.
This is all assuming that you have complete code on your machine. If you are trying to setup, some third party app, then getting all jars together with appropriate name could be issue as Java ws uses internal caching in your temp folder with strange naming conventions.
If you want to start webstart in eclipse by clicking jnlp file , you can setup preferences in eclipse to open .jnlp file with external tool "javaws".
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The significant problems we face cannot be solved by the same level of thinking that created them -- Albert Einstein