[Play-2.6 Java] Help with a problem not really related to Play

[Enrico Morelli]

I'm developing an application that has to create graph images on fly, Using the application in my computer all works fine. 

When I try to run on the server I receive:

 Unexpected exception[AWTError: Can't connect to X11 window server using '0:0' as the value of the DISPLAY variable.]

I use

import com.mxgraph.swing.mxGraphComponent;

import com.mxgraph.util.mxCellRenderer;

import com.mxgraph.view.mxGraph;

import javax.imageio.ImageIO;

import java.awt.Color;

import java.awt.image.BufferedImage;

libraries to create the graph. The image is saved on Play public folder and showed under a modal window.

I don't understand why the awt has to access to X11 and I don't know how to solve the problem.

The following is the method called by jquery ajax that creates the image:

public Result getInteractionImage() throws IOException {

        DynamicForm requestData = formFactory.form().bindFromRequest();

        Integer lig_id = Integer.parseInt(requestData.get("lig_id"));

        String typo = requestData.get("typo");

        List<? extends InteractionHbond> interactions;

        if(typo.equals("1")) {

            interactions = ihbond.findByLigId(lig_id);

        } else {

            interactions = ivwd.findByLigId(lig_id);

        }

        //System.out.println(lig_id);

        mxGraph graph = new mxGraph();

        Object parent = graph.getDefaultParent();

        Boolean first = Boolean.TRUE;

        Object v1 = null;

        Object v = null;

        Integer y = 150;

        graph.getModel().beginUpdate();

        List<String> nBorList = new ArrayList<>();

        for (InteractionHbond ib : interactions) {

            for (Atom at : ib.getAtoms()) {

                String[] neigRes = at.getNeigh_atom_str().split(" ");

                if(first) {

                    String[] ligRes = at.getLig_atom_str().split(" ");

                    v1 = graph.insertVertex(parent, null, ligRes[0]+"_"+ligRes[1], 20, 20, 80,

                            30, "shape=ellipse;perimeter=ellipsePerimeter;strokeColor=blank;fillColor=violet");

                    first = Boolean.FALSE;

                }

                if(!nBorList.contains(neigRes[0]+"_"+neigRes[1])) {

                    nBorList.add(neigRes[0]+"_"+neigRes[1]);

                    v = graph.insertVertex(parent, null, neigRes[0]+"_"+neigRes[1], 240, y,

                        80, 30, "shape=ellipse;perimeter=ellipsePerimeter;strokeColor=black;fillColor=orange");

                    graph.insertEdge(parent, null, "", v1, v);

                    y +=50;

                }

            }

        }

        graph.getModel().endUpdate();

        mxGraphComponent graphComponent = new mxGraphComponent(graph);

        BufferedImage image = mxCellRenderer.createBufferedImage(graph, null, 1, Color.white, true, null);

        ImageIO.write(image, "PNG", new File("public/metalweb/images/" + lig_id + "_" + typo + ".png"));

        String img = "<img src=\"/assets/metalweb/images/" + lig_id + "_" + typo + ".png\" >";

        return ok(img);

    }

Is there a solution?

[Brian Smith]

A bunch of native code in java.awt relies on there being a display available.

You can try setting -Djava.awt.headless=true which will cause it to try and run in headless mode and throw if you execute code that needs a display - from distant memory I think that's ok for Images.

If not I think your options are:

- rewrite to avoid AWT 

- run an xhead (maybe one is already running just not accessible on 0:0 i.e. wrong DISPLAY or permissions)

Best of luck.

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[Enrico Morelli]

On Friday, September 15, 2017 at 7:41:33 PM UTC+2, BrianS wrote:

A bunch of native code in java.awt relies on there being a display available.

You can try setting -Djava.awt.headless=true which will cause it to try and run in headless mode and throw if you execute code that needs a display - from distant memory I think that's ok for Images.

If not I think your options are:

- rewrite to avoid AWT 

- run an xhead (maybe one is already running just not accessible on 0:0 i.e. wrong DISPLAY or permissions)

Best of luck.

Thank you for you answer. I tried to use the first suggestion but I receive:

play.api.UnexpectedException: Unexpected exception[HeadlessException: null]

at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:251)

at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:182)

at play.core.server.AkkaHttpServer$$anonfun$$nestedInanonfun$executeHandler$1$1.applyOrElse(AkkaHttpServer.scala:251)

at play.core.server.AkkaHttpServer$$anonfun$$nestedInanonfun$executeHandler$1$1.applyOrElse(AkkaHttpServer.scala:250)

at scala.concurrent.Future.$anonfun$recoverWith$1(Future.scala:412)

at scala.concurrent.impl.Promise.$anonfun$transformWith$1(Promise.scala:37)

at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:60)

at play.api.libs.streams.Execution$trampoline$.executeScheduled(Execution.scala:109)

at play.api.libs.streams.Execution$trampoline$.execute(Execution.scala:71)

at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:68)

Caused by: java.awt.HeadlessException: null

at java.awt.dnd.DragSource.<init>(DragSource.java:258)

at com.mxgraph.swing.handler.mxGraphHandler.installDragGestureHandler(Unknown Source)

at com.mxgraph.swing.handler.mxGraphHandler.<init>(Unknown Source)

at com.mxgraph.swing.mxGraphComponent.createGraphHandler(Unknown Source)

at com.mxgraph.swing.mxGraphComponent.createHandlers(Unknown Source)

at com.mxgraph.swing.mxGraphComponent.<init>(Unknown Source)

at controllers.ResultController.getInteractionImage(ResultController.java:199)

at router.Routes$$anonfun$routes$1.$anonfun$applyOrElse$20(Routes.scala:331)

at play.core.routing.HandlerInvokerFactory$$anon$3.resultCall(HandlerInvoker.scala:136)

at play.core.routing.HandlerInvokerFactory$$anon$3.resultCall(HandlerInvoker.scala:135)

 

[Brian Smith]

I'm afraid it looks like the mxgraph library you're using for generating / processing images touches parts of awt where a display is required, or at least the way you are using it does.

Some ideas:

- try also unsetting DISPLAY in the env, I've seen reports of java ignoring the headless setting if there's a DISPLAY set

- failing that the simplest solution will be to run a display manager or something like xvfb on the server

- you could see if setting various options in mxgraph avoids the calls to awt that need a display (your stack trace indicates you have a component with drag and drop enabled which I'm sure can't be a requirement on server side, can that be configured off?)

- you could use an alternative to mxgraph for generating your images

Hope that helps

Brian

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[Enrico Morelli]

On Monday, September 18, 2017 at 10:14:09 PM UTC+2, BrianS wrote:

I'm afraid it looks like the mxgraph library you're using for generating / processing images touches parts of awt where a display is required, or at least the way you are using it does.

Some ideas:

- try also unsetting DISPLAY in the env, I've seen reports of java ignoring the headless setting if there's a DISPLAY set

- failing that the simplest solution will be to run a display manager or something like xvfb on the server

- you could see if setting various options in mxgraph avoids the calls to awt that need a display (your stack trace indicates you have a component with drag and drop enabled which I'm sure can't be a requirement on server side, can that be configured off?)

- you could use an alternative to mxgraph for generating your images

Hope that helps

Brian

I tried to unset DISPLAY but I obtain the same exception. In reality the mxgraph (https://jgraph.github.io/mxgraph/docs/manual_javavis.html ) doesn't use awt, I think. I use awt to save image on disk as you see in the method code. I didn't find other way to save the image on disk, if you know other methods I'm happy to know.

[Igmar Palsenberg]

mxgraph uses X11 to do the actual rendering, and it needs a X11 server running. Your best option : Switch over to something else.

Igmar

 

[Enrico Morelli]

On Tuesday, September 19, 2017 at 3:07:16 PM UTC+2, Igmar Palsenberg wrote:

mxgraph uses X11 to do the actual rendering, and it needs a X11 server running. Your best option : Switch over to something else.

Igmar

 

Thanks. Someone know an alternative java library to create graph ?