Web App Libraries empty in Eclipse - no “jars” found

For me, the fix was simple:

• Go here in the Eclipse menu: Project | Properties | Project Facets
• Ensure "Java" and "Dynamic Web Project" are selected
• Click OK

You may need to also do this:

• Go here in the Eclipse menu: Project | Properties | Java Build Path | Libraries
• Remove "Web App Libraries"
• Click "Add Library"
• Choose "Web App Library". Click "Next"
• Choose your project in the drop down
• Click OK