ArrayStoreException on JUNG VisualizationImageServer initialization

I'm trying to get a basic JUNG graph example running - I was able to get the following code to run in a standalone java program but when I put the same code in a server-side jar built using Maven, it fails with a ArrayStoreException on the VisualizationImageServer initialization:

public Response getGraph() throws IOException {
    //log.info("Starting graph rendering");
    try {
        DirectedSparseGraph<String, Number> g = new DirectedSparseGraph();
        String[] v = createVertices(10); 
        createEdges(v); 
        vv =  new VisualizationImageServer<String,Number>(new KKLayout<String,Number>(graph), new Dimension(600,600)); 
        renderGraph(vv);
        ...}

This line fails:

        vv =  new VisualizationImageServer<String,Number>(new KKLayout<String,Number>(graph), new Dimension(600,600));

Error message snippet:

java.lang.ArrayStoreException: edu.uci.ics.jung.algorithms.layout.KKLayout
    at edu.uci.ics.jung.visualization.layout.ObservableCachingLayout.<init>(ObservableCachingLayout.java:50)
    at edu.uci.ics.jung.visualization.DefaultVisualizationModel.setGraphLayout(DefaultVisualizationModel.java:91)
    at edu.uci.ics.jung.visualization.DefaultVisualizationModel.<init>(DefaultVisualizationModel.java:74)
    at edu.uci.ics.jung.visualization.BasicVisualizationServer.<init>(BasicVisualizationServer.java:150)
    at edu.uci.ics.jung.visualization.VisualizationImageServer.<init>(VisualizationImageServer.java:40)

Solution

My best guess is that on your server side code, you have more than one version of jung that conflict with each other. On line 50 of ObservableCachingLayout in jung-visualization version 2.0, the delegate (KKLayout) is added to a org.apache.commons.collections15.Transformer[] array, because the KKLayout delegate is (supposed to be) an instance of a Transformer. Your array store exception that calls out the KKLayout as the problem makes me think that the earlier version 2.0 of ObservableCachingLayout is getting a version 2.1 or later KKLayout delegate (from jung-algorithms) that is not a Transformer, but is instead a com.google.common.base.Function. I can't verify that this is the actual problem, but I believe that this theory addresses a possible cause of the specific errors you are seeing.