Eclipse: creating a weblogic-enabled project

When you create a Java project, it's NOT faceted

This project is not configured to use project facets. Converting this project to faceted form will allow you to easily control the available technologies.

and its .project file contains:

<?xml version="1.0" encoding="UTF-8"?>
<projectDescription>
 <name>WLExtensions</name>
 <comment></comment>
 <projects>
 </projects>
 <buildSpec>
  <buildCommand>
   <name>org.eclipse.jdt.core.javabuilder</name>
   <arguments>
   </arguments>
  </buildCommand>
 </buildSpec>
 <natures>
  <nature>org.eclipse.jdt.core.javanature</nature>
 </natures>
</projectDescription>

if you click on "convert to faceted form" you get an extra builder org.eclipse.wst.common.project.facet.core.builder in the .project, and an extra org.eclipse.wst.common.project.facet.core.nature nature

Once you have a faceted project, you can associate it to a Runtime:

which allows you to enable WebLogic System libraries:

Let's be frank, it could be simpler. Even because NOT all WebLogic classes are available in the System Libraries, often one has to hunt right and left for the right jar.