[TAPESTRY-1177] ForBean can cause NullPointerException when rendered without a template

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 4.1.1
• Fix Version/s: 4.1.1
• Component/s: Framework
• Assignee: Jesse Kuhnert
• Reporter: Phil McCarthy
• Created: 08/Dec/06 10:13
• Updated: 08/Dec/06 21:00
• Resolved: 08/Dec/06 21:00

Description

Create a component which doesn't implement ITemplateComponent. In the component specification, declare a For component, but don't bind its optional "element" parameter. Call the For component's render() method.

Stacktrace is:

java.lang.NullPointerException
Stack Trace:

• org.apache.tapestry.markup.MarkupWriterImpl.end(MarkupWriterImpl.java:261)
• org.apache.tapestry.components.ForBean.renderComponent(ForBean.java:183)
• ...

The problem is caused by line 140 of ForBean.java:

String element = HiveMind.isNonBlank(getElement()) ? getElement() : getTemplateTagName();

Because no element binding was specified, and there's no template, this returns null. The markup writer pushes the null value when begin(null) is called, then barfs when it is popped in end().

Fix is to not call loopWriter.begin()/end() when element is null.