Error After Switching Oxygen Products in Eclipse

Problem

On an Eclipse deployment, after installing and using the Editor product, I later decided to uninstall it and use Author or Developer instead. After installing the new product, I received an error that looked like this:
java.lang.Exception
      at org.eclipse.ui.internal.ViewReference.createErrorPart(ViewReference.java:112)
      at org.eclipse.ui.internal.ViewReference.createPart(ViewReference.java:98)
      at org.eclipse.ui.internal.e4.compatibility.CompatibilityPart.createPart
                                                          (CompatibilityPart.java:279)
      at org.eclipse.ui.internal.e4.compatibility.CompatibilityPart.create
                                                          (CompatibilityPart.java:317)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke
                                                (DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
...

Solution

You need to manually delete the perspective for the product you uninstalled by following this procedure:
  1. Go to Window > Preferences > General > Perspectives.
  2. Select the perspective for the product you uninstalled (for example, <oXygen/> XML) and click Delete.
  3. Restart Eclipse.
  4. Go to Window > Open Perspective and select the perspective for the new product (for example, <oXygen/> XML Author).