How do I open an editor on a file outside the workspace?

Since 3.3 you can use the new EFS support to open an text editor on a file outside the workspace:

   String name =   new  FileDialog(aShell, SWT.OPEN).open();
    if  (name  ==   null )
       return ;
   IFileStore fileStore =   EFS.getLocalFileSystem().getStore( new  Path(filterPath));
   fileStore =   fileStore.getChild(names[i]);
    if  ( ! fileStore.fetchInfo().isDirectory()  &&  fileStore.fetchInfo().exists())  ... {
     IWorkbenchPage page=  window.getActivePage();
     try ...{
       IDE.openEditorOnFileStore(page, fileStore);
     } catch (PartInitException e) ...{
       /**//* some code */
     }

Alternatively, you can create a linked resource in an existing project, which points to a file elsewhere in the file system. This example snippet creates a project called “External Files,” and then prompts the user to select any file in the file system. The code then creates a linked resource in the project to that external file, allowing the platform to open the file in read/write mode in one of the standard editors:

 
  
  
  
  

  
  
  
  
  
 
  
 
  
   
   
   
   
 
     
       IWorkspace ws  
    = 
     ResourcesPlugin.getWorkspace();
   IProject project  
    = 
     ws.getRoot().getProject( 
    " 
    External Files 
    " 
    );
    
    if 
     ( 
    ! 
    project.exists())
      project.create( 
    null 
    );
    
    if 
     ( 
    ! 
    project.isOpen())
      project.open( 
    null 
    );
   Shell shell  
    = 
     window.getShell();
   String name  
    = 
      
    new 
     FileDialog(shell, SWT.OPEN).open();
    
    if 
     (name  
    == 
      
    null 
    )
       
    return 
    ;
   IPath location  
    = 
      
    new 
     Path(name);
   IFile file  
    = 
     project.getFile(location.lastSegment());
   file.createLink(location, IResource.NONE,  
    null 
    );
   IWorkbenchPage page  
    = 
     window.getActivePage();
    
    if 
     (page  
    != 
      
    null 
    )
      page.openEditor(file);