[WW-4663] NullPointerException when displaying a form without action attribute

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.3.28, 2.3.29, 2.3.30
• Fix Version/s: 2.5.12
• Assignee: Lukasz Lenart
• Reporter: Yan Soulliaert
• Created: 20/Jul/16 10:06
• Updated: 13/Jul/17 19:28
• Resolved: 04/Apr/17 07:17

Description

Hello,

I'm currently trying to upgrade Struts from V2.3.20 to V2.3.30.
Starting from V2.3.28, I'm having a yellow FreeMarker stack at the end of some pages. These pages have a <s:form> tag without "action" attribute.

Here is some part of the displayed error :

Java method "org.apache.struts2.components.Form.getValidators(String)" threw an exception when invoked on org.apache.struts2.components.Form object "org.apache.struts2.components.Form@3d354929"; see cause exception in the Java stack trace.
FTL stack trace ("~" means nesting-related):
	- Failed at: #list tag.getValidators("\$\{tagName\}"...  [in template "template/~~~css_xhtml/form-close-validate.ftl" at line 66, column 9]
	- Reached through: #include "/\$\{parameters.templateDir\}...  [in template "template/xhtml/form-close.ftl" at line 25, column 1]
...
Caused by: java.lang.NullPointerException
	at org.apache.struts2.util.ComponentUtils.containsExpression(ComponentUtils.java:51)
	at org.apache.struts2.components.Component.findValue(Component.java:376)
	at org.apache.struts2.components.Component.findString(Component.java:226)
	at org.apache.struts2.components.Form.getValidators(Form.java:276)

Here are the results of my research :

• When the method org.apache.struts2.components.Form.getValidators(String name) is called at the end of the page display, the "action" var is null.
• findString(action) is called, leading to org.apache.struts2.components.Component.findValue(String expr, Class toType) with expr=null
• Starting from V2.3.28, a new condition has been added to this method : if (ComponentUtils.containsExpression(expr)). This raises the NPE.

Is this a bug, or am I doing something wrong ?

Thanks in advance,
Yan