Exception when "pulling changes" from local database

[m-mauersberger]

JabRef 5.2--2020-09-29--2d92025
Linux 4.12.14-lp151.28.67-default amd64
Java 15

• I have tested the latest development version from http://builds.jabref.org/master/ and the problem persists

Steps to reproduce the behavior:

1. Load a local database.
2. Click on "Pull changes from shared database"
3. Exception has been thrown.

Log File

java.lang.NullPointerException: Cannot invoke "org.jabref.logic.shared.DatabaseSynchronizer.pullChanges()" because "<local1>" is null
      at org.jabref.gui.shared.PullChangesFromSharedAction.lambda$execute$0(Unknown Source) ~[org.jabref:?]
      at java.util.Optional.ifPresent(Unknown Source) ~[?:?]
      at org.jabref.gui.shared.PullChangesFromSharedAction.execute(Unknown Source) ~[org.jabref:?]
      at org.jabref.gui.actions.JabRefAction.lambda$new$2(Unknown Source) ~[org.jabref:?]
      at org.controlsfx.control.action.Action.handle(Unknown Source) ~[org.jabref.merged.module:?]
      at org.controlsfx.control.action.Action.handle(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at javafx.event.Event.fireEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at javafx.scene.control.MenuItem.fire(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.scene.control.ContextMenuContent$MenuItemContainer.doSelect(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.scene.control.ContextMenuContent$MenuItemContainer.lambda$createChildren$12(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at javafx.event.Event.fireEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at javafx.scene.Scene$MouseHandler.process(Unknown Source) ~[org.jabref.merged.module:?]
      at javafx.scene.Scene.processMouseEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at javafx.scene.Scene$ScenePeerListener.mouseEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source) ~[org.jabref.merged.module:?]
      at java.security.AccessController.doPrivileged(Unknown Source) ~[?:?]
      at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.glass.ui.View.handleMouseEvent(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.glass.ui.View.notifyMouse(Unknown Source) ~[org.jabref.merged.module:?]
      at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method) ~[org.jabref.merged.module:?]
      at com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$11(Unknown Source) ~[org.jabref.merged.module:?]
      at java.lang.Thread.run(Unknown Source) [?:?]

[Siedlerchr]

The solution would be to create another BooleanExpression in the ActionHelper class, e..g needsSharedDatabase
filter there
And in the action you can then bind it, e..g:
this.executable.bind(ActionHelper.needsEntriesSelected(stateManager));

[luis-valdez]

Hi! Can I work on this?

[Siedlerchr]

Sure. Go ahead, if you have any questions ask here or in our gitter channel

[luis-valdez]

Hello I'm back. I think I have a solution almost worked out but I need a little help.

I added the binding in PullChangesFromSharedAction.java

    public PullChangesFromSharedAction(StateManager stateManager) {
        this.stateManager = stateManager;

        this.executable.bind(ActionHelper.needsDatabase(stateManager));
        this.executable.bind(ActionHelper.needsSharedDatabase(stateManager)); //new
    }

The problem is I'm still not sure how to make the validation in the ActionHelper.java. So far my approach is something like this:

    public static BooleanExpression needsSharedDatabase(StateManager stateManager){
        return stateManager.activeDatabaseProperty().isEqualTo("shared");
    }

The problem is that in the .isEqualTo I'm not sure with what I should compare it to detect when the user is not using a shared database.

I would really appreciate some help to make my first contribution!

[Siedlerchr]

Idea is good so far, for checking if it's a shared database you better check the bibdatabasecontect e.g
databaseContext.getLocation() == DatabaseLocation.SHARED)

[calixtus]

Bindings.createBooleanBinding is probably your friend here. Be aware that you can combine two Bindings with .and()

[luis-valdez]

Update:

I came up with this solution:

    public static BooleanExpression needsSharedDatabase(StateManager stateManager) {
        BibDatabaseContext databaseContext = stateManager.activeDatabaseProperty().orElse(null).get();
        return Bindings.createBooleanBinding(() -> databaseContext != null && databaseContext.getLocation() == DatabaseLocation.SHARED);
    }

But now the problem is that the validation is only being done at the start when I run the program. I'm guessing It's related to the StateManager.java but I'm fairly new to JavaFX so I'll keep looking into it.

[Siedlerchr]

You need to add the check for the active database property in the booleanBinding itself. The Bindings are wrapper around Observables. Observables update whenever their values changes.
Some background info: https://docs.oracle.com/javase/8/javafx/properties-binding-tutorial/binding.htm

I think something like this could work:
you may need to add some null checks

     var binding = Bindings.createBooleanBinding(()->
        stateManager.activeDatabaseProperty().getValue().filter(context->context.getLocation() == DatabaseLocation.SHARED).isPresent(),
        stateManager.activeDatabaseProperty());
  
        return BooleanExpression.booleanExpression(binding);

[luis-valdez]

Thanks a lot @Siedlerchr I really appreciate your help. I'll look into it.

[calixtus]

orElse(null) is always a bad idea...
Try using .isEmpty() inside the lambda expression.