I tried making a windows-explorer tree using a richfaces:tree... At first I tried storing my tree state in conversation context, but then I had bugs because the richfaces tree would not always pass the correct conversation context when clicking on nodes. So then I stored my tree state in the session... but then I got LazyInitializationExceptions. So then I tried using the unseamly approach of using a session-scoped entityManager. But then I had various of other bugs with the tree, and it was really slow... so then I got rid of it and decided to display my tree structure using regular html links. No bugs, and much faster. This was with richfaces 3.0.1 though... I saw that they made improvements in 3.1.0 (like recursiveTreeNodeAdapter) but my experience with with the 3.0.1 was so buggy and slow I don't want to try it again.

http://fisheye.jboss.com/browse/~raw,r=1.1/JBoss/jboss-seam/examples/wiki/src/main/org/jboss/seam/wiki/core/nestedset/package.html

http://fisheye.jboss.com/browse/JBoss/jboss-seam/examples/wiki/src/main/org/jboss/seam/wiki/core/nestedset

 public TreeNode getTree() {
 if (directoryTree == null) {
 directoryTree = new WikiTreeNodeAdapter(getInstance(), getNodeDAO().getComparatorDisplayPosition(), 2l);
 directoryTree.loadChildren();
 }
 }

 <h:form id="dirTree" rendered="false">
 <ui:include src="includes/statusIndicator.xhtml"/>

 #{directoryHome.instance.name}:
 <rich:tree value="#{directoryHome.tree}" var="nodeWrapper"
 switchType="ajax" status="dirTree\:status"
 nodeFace="#{wiki:getType(nodeWrapper.wrappedNode)}">

 <rich:treeNode type="Directory">
 <f:facet name="icon">
 <h:graphicImage value="/themes/#{wikiPreferences.themeName}/img/icon.dir.gif" width="18" height="20"/>
 </f:facet>
 <f:facet name="iconLeaf">
 <h:graphicImage value="/themes/#{wikiPreferences.themeName}/img/icon.dir.gif" width="18" height="20"/>
 </f:facet>
 <h:outputText value="#{nodeWrapper.wrappedNode.name}"/> (#{nodeWrapper.level})
 </rich:treeNode>

 <rich:treeNode type="Document">
 <f:facet name="icon">
 <h:graphicImage value="/themes/#{wikiPreferences.themeName}/img/icon.doc.gif" width="18" height="20"
 rendered="#{nodeWrapper.wrappedNode != nodeWrapper.wrappedParent.wrappedNode.defaultDocument}"/>
 <h:graphicImage value="/themes/#{wikiPreferences.themeName}/img/icon.doc.default.gif" width="18" height="20"
 rendered="#{nodeWrapper.wrappedNode == nodeWrapper.wrappedParent.wrappedNode.defaultDocument}"/>
 </f:facet>
 <f:facet name="iconLeaf">
 <h:graphicImage value="/themes/#{wikiPreferences.themeName}/img/icon.doc.gif" width="18" height="20"
 rendered="#{nodeWrapper.wrappedNode != nodeWrapper.wrappedParent.wrappedNode.defaultDocument}"/>
 <h:graphicImage value="/themes/#{wikiPreferences.themeName}/img/icon.doc.default.gif" width="18" height="20"
 rendered="#{nodeWrapper.wrappedNode == nodeWrapper.wrappedParent.wrappedNode.defaultDocument}"/>
 </f:facet>
 <h:outputText value="#{nodeWrapper.wrappedNode.name}"/> (#{nodeWrapper.level})
 </rich:treeNode>

 <rich:treeNode type="File">
 <f:facet name="icon">
 <h:graphicImage value="/themes/#{wikiPreferences.themeName}/img/#{fileMetaMap[nodeWrapper.wrappedNode.contentType].displayIcon}"
 width="18" height="20"
 rendered="#{!empty fileMetaMap[nodeWrapper.wrappedNode.contentType]}"/>
 <h:graphicImage value="/themes/#{wikiPreferences.themeName}/img/#{fileMetaMap['generic'].displayIcon}"
 width="18" height="20"
 rendered="#{empty fileMetaMap[nodeWrapper.wrappedNode.contentType]}"/>
 </f:facet>
 <f:facet name="iconLeaf">
 <h:graphicImage value="/themes/#{wikiPreferences.themeName}/img/#{fileMetaMap[nodeWrapper.wrappedNode.contentType].displayIcon}"
 width="18" height="20"
 rendered="#{!empty fileMetaMap[nodeWrapper.wrappedNode.contentType]}"/>
 <h:graphicImage value="/themes/#{wikiPreferences.themeName}/img/#{fileMetaMap['generic'].displayIcon}"
 width="18" height="20"
 rendered="#{empty fileMetaMap[nodeWrapper.wrappedNode.contentType]}"/>
 </f:facet>
 <h:outputText value="#{nodeWrapper.wrappedNode.name}"/> (#{nodeWrapper.level})
 </rich:treeNode>

 </rich:tree>
 </h:form>

I have an extremely similar situation in my app. I have a large tree structure that is displayed on every page. The tree can have arbitrary numbers of nodes so lazy loading is must.

I needed to be able to do drag-n-drop to move nodes and folders. I first tried icefaces but had to give up because of their drag and drop support was pitiful (it had no way to add javascript hooks for things like confirm dialogs --i.e. 'are you sure you want to move this node?'). Then I tried Richfaces, god was that a nightmare. Their tree datastructure is truly bazaar and I found the performance to be horrendous. I basically wasted 4 months on icefaces and richfaces (though it's possible that their implementations have gotten better in recent versions).

Then I tried ext.js and just passed my treenodes via json from a servlet. This solution has been perfect. Tree response is very fast, and I can control the drag and drop operations any way I want (plus their dnd implementation is designed to handle many many nodes).

my 2 cents..

dustin

I save the tree state in the session as its accessed on every page. My node objects are fairly light and I remove the nodes in closed folders (so the memory is freed) so I'm not that concerned about it being a scaling issue. If a user had tens of thousands of nodes viewable at the same time the page would be unusable slow to load.

-Dustin