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POJSF ViewHandlerWrapper causes NullPointerException
 

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  1. POJSF ViewHandlerWrapper causes NullPointerException
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    <p>I have a little issue with a JSF ViewHandlerWrapper that I've coded. It works fine most of the times, but at times I will get a NullPointerException from the very core of Mojarra and thus started to wonder whether I implemented my ViewHandlerWrapper correctly.</p> <pre><code>public class TokenViewHandler extends ViewHandlerWrapper { private ViewHandler parent; public TokenViewHandler(ViewHandler parent) { this.parent = parent; } @Override public ViewHandler getWrapped() { return parent; } @Override public void renderView(FacesContext context, UIViewRoot viewToRender) throws IOException, FacesException { final String token = UUID.randomUUID().toString(); findAndModifyForms(viewToRender, token, context); getWrapped().renderView(context, viewToRender); } private void findAndModifyForms(final UIComponent component, final String token, final FacesContext ctx) { if (component instanceof UIForm) { final HtmlInputHidden hidden = (HtmlInputHidden) ctx.getApplication().createComponent(HtmlInputHidden.COMPONENT_TYPE); hidden.setValue(token); component.getChildren().add(hidden); } else { for (UIComponent tempComponent : component.getChildren()) { findAndModifyForms(tempComponent, token, ctx); } } } } </code></pre> <p>From the code you quickly realize that I want to add a <strong>inputHidden</strong>-component with a UUID value to each <strong>form</strong> on the view.</p> <p>As I haven't found any good examples for ViewHandlerWrappers I assumed that it should look like a ExceptionHandlerWrapper but since I get the occassional NPE using my ViewHandler, I assume that something is wrong and I can't seem to see it.</p>
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    1. COWhat line is causing the NPE?
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    2. CONone of the lines in my code. It's in Mojarra itself, which makes it a bit hard to pinpoint. I get java.lang.NullPointerException: null at com.sun.faces.application.view.StateManagementStrategyImpl$4.invokeContextCallback(StateManagementStrategyImpl.java:289) ~[glassfish.jsf_1.0.0.0_2-0-2.jar:2.0.2-FCS] at javax.faces.component.UIComponent.invokeOnComponent(UIComponent.java:1253) ~[javax.jsf_1.0.0.0_2-0.jar:2.0.2-FCS]
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    3. COSeems that the NPE always occours if the next view flows through an Action, i.e. commandLink -> Action -> Outcome. If, however, the view is invoked directly, it works. Weird stuff :) I was checking in the Mojarra sources also, and it seems, that the framework is not aware of the new component unless added earlier. Problem is, if I hook into the lifecycle earlier, the other components have not yet been added to the viewRoot, so I am essentially stuck.
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