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https://issues.apache.org/jira/browse/TAP5-2745?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ben Weidig resolved TAP5-2745.
------------------------------
Fix Version/s: 5.8.3
Resolution: Fixed
> Tree component with empty list of root nodes causes NullPointerException
> ------------------------------------------------------------------------
>
> Key: TAP5-2745
> URL: https://issues.apache.org/jira/browse/TAP5-2745
> Project: Tapestry 5
> Issue Type: Bug
> Components: tapestry-core
> Affects Versions: 5.8.2
> Reporter: Robert Hailey
> Assignee: Ben Weidig
> Priority: Major
> Labels: patch
> Fix For: 5.8.3
>
> Attachments: TAP5-2745-suggested-fix.patch
>
>
> An edge case, perhaps, but it seems as though attempting to create a Tree
> component with no root nodes does not produce an empty list, but throws a
> null pointer exception.
> {noformat}
> java.lang.NullPointerException: Cannot invoke
> "org.apache.tapestry5.tree.TreeNode.getValue()" because "this.val$node" is
> null
> at org.apache.tapestry5.corelib.components.Tree$4.render(Tree.java:169)
> ~[tapestry-core-5.8.2.jar:?]
> at
> org.apache.tapestry5.internal.services.RenderQueueImpl.run(RenderQueueImpl.java:79)
> ~[tapestry-core-5.8.2.jar:?]
> at
> org.apache.tapestry5.internal.services.PageRenderQueueImpl.render(PageRenderQueueImpl.java:121)
> ~[tapestry-core-5.8.2.jar:?]
> {noformat}
> To the best of my understanding, the fix is straight forward:
> {noformat}
> ---
> a/tapestry-core/src/main/java/org/apache/tapestry5/corelib/components/Tree.java
> +++
> b/tapestry-core/src/main/java/org/apache/tapestry5/corelib/components/Tree.java
> @@ -265,7 +265,12 @@ public class Tree
> writer.element("ul");
> queue.push(RENDER_CLOSE_TAG);
>
> - queue.push(toRenderCommand(nodes.first(), true));
> + TreeNode first = nodes.first();
> +
> + if (first != null)
> + {
> + queue.push(toRenderCommand(first, true));
> + }
>
> nodes.rest().each(new Worker<TreeNode>()
> {
> {noformat}
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