Question

I received a ConcurrentNodificationException when I implemented a rich:tree with dynamic loading of the nodes.

I’m using JSF1.2, Tomcat 6.0, RichFaces 3.3.3, and Java 6u31.

in JSF page I have this rich tree component

<rich:tree id="treeAreas" value="#{areaArmazenamento.treeAreas}"
    var="node"
    adviseNodeOpened="#{storageArea.adviseNodeOpenedTreeAreas}"
    adviseNodeSelected="#{storageArea.adviseNodeSelectedTreeAreas}"
    ajaxSubmitSelection="true"
    componentState="#{storageArea.treeAreasState}"
    nodeSelectListener="#{storageArea.selectNodeArea}"
    nodeFace="#{node.type}" similarityGroupingId="true"
    ondragstart="hideContextMenu();" disableKeyboardNavigation="true"
    rightClickSelection="true" toggleOnClick="true" requestDelay="150"
    changeExpandListener="#{storageArea.expandNodeListener}">

In Managed Bean storageArea I’have the code that load nodes, and on first time the method is called the first level of nodes is loaded, when a click in a node the substructure of this node is loaded.

On load the first level is validated the user’s permissions, and this validation use the iterator of list that stores the tree nodes, this validation remove nodes that the user access is denied. some like this:

List<AreaArmazenamento> areas = root.getPastas();
synchronized (areas) {      
    Iterator<AreaArmazenamento> it = areas.iterator();
    while(it.hasNext())
    {
        area = it.next();
        boolean havePermission = ControllerPermission.havePermission(null, area, Permissions.VIEW, false);
        if(!havePermission)
        {
                it.remove();
        }
    }
}

When I click on any node, I select the sub nodes of database and add the substructure in selected node, this working but sometimes on select node is throwed a ConcurrentNodificationException on Hashtable which is in TreeDataModule of Rich Tree.

This is a trace of exception:

Caused by: java.util.ConcurrentModificationException
at java.util.Hashtable$Enumerator.next(Hashtable.java:1031)
at org.richfaces.model.TreeDataModel.doWalk(TreeDataModel.java:136)
at org.richfaces.model.TreeDataModel.doWalk(TreeDataModel.java:154)
at org.richfaces.model.TreeDataModel.doWalk(TreeDataModel.java:154)
at org.richfaces.model.TreeDataModel.walk(TreeDataModel.java:178)
at org.richfaces.component.UITree.walk(UITree.java:422)
at org.richfaces.renderkit.TreeRendererBase.writeContent(TreeRendererBase.java:683)

anything about it may be causing this error? and why?

Answer 1

I Found the problem…

  while(it.hasNext())
{
    area = it.next();
    boolean havePermission = ControllerPermission.havePermission(null, area, Permissions.VIEW, false);
    if(!havePermission)
    {
            it.remove(); //problem here
    }
}

I was removing items from the list on iteration…