The postback key is initialised to a specific value for JSF 1.2 environments, but was left null with JSF 1.1, so it's been given a default value, so as not to be null.

Subversion 18908
icefaces\core\src\com\icesoft\faces\context\BridgeExternalContext.java

The NPE is thrown when doing server pushes with JSF 1.1 Basically, when <ui:debug> renders it makes a copy of the RequestParameterMap, which chokes because of a null key. The null key is from PersistentFacesState.execute() putting in the "not reload" value, under the BridgeExternalContext.PostBackKey key, but BridgeExternalContext.PostBackKey is null.

This is not a problem under JSF 1.2, with or without server push.

In your web.xml, make sure you have the actionURLSuffix context-param set, or else you will get NPE.

<context-param>
<param-name>com.icesoft.faces.actionURLSuffix</param-name>
<param-value>.iface</param-value>
</context-param>

Jacky in QA reports:

[Using a test app created by Mandeep using timezone7]
When tested on tomcat5, I got NPE non-stop. Same one described in the JIRA. On tomcat6, no NPE.
On FF3, debug window shows xml of page instead of debug screen
On IE7, a window shows up for a few sec, closes, then save dialog box appears

This feature has now been ported to ICEfaces. It's been implemented quite differently from stock Facelets, but the result is the same, that the output from the <ui:debug> tag will be served out when the special Facelets UI Debug request is made.

To use this, just add the <ui:debug> tag to your application, and press CONTROL-SHIFT-D in your app. In Firefox 3 that will also bring up a bookmarking dialog, but you can just cancel that.

Subversion 18872
icefaces\core\src\com\icesoft\faces\context\View.java
icefaces\core\src\com\icesoft\faces\facelets\FaceletsUIDebug.java

http://www.icefaces.org/JForum/posts/list/12109.page
Another forum user noticed this issue.

Following behaviour was seen when timezone7 (ICEFaces trunk revision# 18187) was tested with ui:debug tag:
1) on pressing Ctrl+Shift+d a window with url "http://localhost:8080/timezone7/timezone.xhtml?facelets.ui.DebugOutput=1232404227498" was opened. That simple displayed page code (screen shot attached)
2) Also NullPointerException was seen on Tomcat5 ( Tomcat6 server showed no exceptions)
Jan 19, 2009 3:35:40 PM com.icesoft.faces.facelets.D2DFaceletViewHandler renderR
esponse
SEVERE: Problem in renderResponse: null
java.lang.NullPointerException
at java.lang.String.compareTo(String.java:997)
at java.lang.String.compareTo(String.java:90)
at java.util.TreeMap.compare(TreeMap.java:1093)
at java.util.TreeMap.put(TreeMap.java:465)
at java.util.AbstractMap.putAll(AbstractMap.java:317)
at java.util.TreeMap.putAll(TreeMap.java:328)
at java.util.TreeMap.<init>(TreeMap.java:156)
at com.sun.facelets.util.DevTools.writeVariables(DevTools.java:158)
at com.sun.facelets.util.DevTools.writeVariables(DevTools.java:144)
at com.sun.facelets.util.DevTools.debugHtml(DevTools.java:135)
at com.sun.facelets.tag.ui.UIDebug.writeDebugOutput(UIDebug.java:92)
at com.sun.facelets.tag.ui.UIDebug.encodeBegin(UIDebug.java:81)
at com.icesoft.faces.application.D2DViewHandler.renderResponse(D2DViewHandler.java:551)
at com.icesoft.faces.application.D2DViewHandler.renderResponse(D2DViewHandler.java:559)
at com.icesoft.faces.application.D2DViewHandler.renderResponse(D2DViewHandler.java:559)
at com.icesoft.faces.application.D2DViewHandler.renderResponse(D2DViewHandler.java:559)
at com.icesoft.faces.facelets.D2DFaceletViewHandler.renderResponse(D2DFaceletViewHandler.java:282)
at com.icesoft.faces.application.D2DViewHandler.renderView(D2DViewHandler.java:156)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:107)
at com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:245)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:137)
at com.icesoft.faces.webapp.xmlhttp.PersistentFacesState.render(PersistentFacesState.java:175)
at com.icesoft.faces.webapp.xmlhttp.PersistentFacesState.executeAndRender(PersistentFacesState.java:299)
at com.icesoft.faces.async.render.RunnableRender.run(RunnableRender.java:143)
at edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:665)
at edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:690)
at java.lang.Thread.run(Thread.java:595)

Following behaviour was seen for non icefaces page:

1)Correct debug page with following url is displayed "http://localhost:8080/timezone7/timezone.jsf?facelets.ui.DebugOutput=1232404864673"
screen shot attached.
Following javascipt was seen on the page
//<![CDATA[
function faceletsDebug(URL)

;var faceletsOrigKeyup = document.onkeyup; document.onkeyup = function(e)

;
//]]>