package xuml.tools.diagram;
   
   import xuml.tools.datastore.DatastoreText;
   import xuml.tools.datastore.DatastoreTextFactory;
   import xuml.tools.datastore.memory.DatastoreTextFactoryMemory;
   
   public class Context {
   
       private static Context instance;
  
      public synchronized static Context instance() {
          if (instance == null)
              instance = new Context();
          return instance;
      }
  
      private Context() {
          // disable constructor outside of this class
          // must use static instance
      }
  
      private DatastoreTextFactory datastoreFactory = new DatastoreTextFactoryMemory();
      private DatastoreText datastore;
  
      public void setDatastoreFactory(DatastoreTextFactory datastoreFactory) {
          this.datastoreFactory = datastoreFactory;
      }
  
      public synchronized DatastoreText getDatastore() {
          if (datastore == null)
              datastore = datastoreFactory.create();
          return datastore;
      }
  }