When you open a file in JDeveloper, the mode that is used as the default might not be what you as a developer want.  If, for example, every time you open a .jsp(x) file you click on the source tab at the bottom of the window so that you can edit the jsp(x) file in source code mode, you may want to consider changing the default editor for that file type.  This is easy to do in the JDeveloper tool preferences and can be a time saver in the long run, since some editors can take a while to start up and if you don't need them often, this would just be lost time.  Here are the steps:
 

1. From the JDeveloper menu, select Tools->Preferences...
2. Select "File Types" in the tree component on the left side of the preferences dialog.
3. Click on the "Default Editors" tab.
4. Scroll to the file type you want to change.
5. In the details section at the bottom of the dialog, use the "Default Editor" select list to change the default to your liking.