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Subject: NullPointerException 5.5.17 Request.setAttribute(Request.java:1376)
Date: Tue, 19 Aug 2008 16:05:00 +1000
Message-ID: 
 <82A68136DC5559418D5FDB1EECBC7F9E01CFA10A@bne-extemp1.nti.internal>
Thread-Topic: NullPointerException 5.5.17
 Request.setAttribute(Request.java:1376)
Thread-Index: AckBwYO+T/X8UeLISeyaOWGHTtf/tw==
From: Adam Jenkins <AdamJenkins@nti.com.au>
To: <users@tomcat.apache.org>

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Hi=20All,
I'be=20been=20tearing=20my=20hair=20out=20for=20a=20couple=20of=20weeks=20=
over=20this=20one=20and=20would=20appreciate=20any=20assistance=20anyone=20=
could=20give.=20=20It's=20a=20bit=20of=20a=20unique=20scenario,=20so=20it'=
ll=20take=20me=20a=20little=20while=20to=20explain:
We=20have=20a=20legacy=20struts=20app,=20forwarding=20to=20a=20jsf=20app=20=
(details=20of=20how=20below)=20running=20on=20tomcat=205.5.17.=20=2099.9%=20=
of=20the=20time=20everythign=20works=20great,=20but=20every=20now=20and=20=
then=20(which=20in=20users=20speak=20translates=20to=20'I=20keep=20on=20ge=
tting',=20hence=20we=20can't=20ignore=20it)=20a=20NullPointerException=20g=
ets=20thrown=20from=20org.apache.catalina.connector.Request.setAttribute.
The=20flow=20is:
Third=20party=20application=20---<<http=20redirect>>--->=20JSFBridgeFilter=
=20(will=20explain=20later)=20----->=20Struts=20application=20---->=20JSFB=
ridge--->JSF=20Application--->Response=20back=20to=20third=20party=20app.
The=20struts=20application=20contains=20proprietary=20logic=20to=20interfa=
ce=20with=20the=20third=20party=20app,=20so=20we=20can't=20get=20rid=20of=20=
it.=20Business=20wants=20all=20development=20internally=20to=20be=20done=20=
in=20JSF,=20so=20we=20can't=20get=20rid=20of=20that.
The=20JSFBridgeFilter=20instantiates=20the=20JSF=20Context=20for=20later=20=
use,=20and=20wraps=20the=20request=20that=20is=20used=20to=20instantiate=20=
it=20in=20a=20request=20wrapper=20that=20translates=20".do"=20context=20pa=
ths=20to=20".jsf"=20context=20paths=20(otherwise=20all=20the=20forms=20sub=
mit=20back=20to=20".do"=20after=20coming=20from=20the=20struts=20framework=
.=20=20It=20looks=20like=20this:
public=20void=20doFilter(ServletRequest=20strutsRequest,=20ServletResponse=
=20response,=20FilterChain=20chain)=20throws=20IOException,=20ServletExcep=
tion=20{

HttpServletRequest=20jsfRequest=20=3D=20new=20StrutsToJsfRequestWrapper((H=
ttpServletRequest)strutsRequest);

JSFBridge.getFacesContext(viewId,=20(HttpServletRequest)jsfRequest,=20(Htt=
pServletResponse)response);

chain.doFilter(strutsRequest,=20response);=20

}

...and=20the=20StrutsToJsfRequestWrapper=20contains=20only=20one=20overrid=
e=20method=20(it=20extends=20HttpServletRequestWrapper):
@Override

public=20String=20getServletPath()=20{

=09String=20oldPath=20=3D=20super.getServletPath();

=09String=20newPath=20=3D=20null;

=09int=20index=20=3D=20oldPath.lastIndexOf(".do");

=09if=20(index=20>=3D=200)=20{

=09=09newPath=20=3D=20oldPath.substring(0,=20index=20+=201)=20+=20".jsf";

=09}=20else=20{

=09=09newPath=20=3D=20oldPath;

=09}

=09return=20newPath;

}

=20

Now,=20you'll=20notice=20in=20the=20filter=20that=20the=20request=20wrappe=
r=20is=20used=20to=20instantiate=20the=20faces=20context,=20and=20the=20or=
iginal=20request=20passed=20onto=20the=20struts=20application.=20=20The=20=
'getFacesContext'=20method=20implements=20some=20code=20from=20the=20apach=
e=20myfaces=20wiki=20that=20shows=20a=20way=20to=20call=20into=20the=20JSF=
=20framework=20from=20non=20jsf=20artifacts:

=20

It=20looks=20like=20this:

=20

public=20class=20JSFBridge=20{

=20

=09private=20abstract=20static=20class=20InnerFacesContext=20extends=20Fac=
esContext=20{

=09=09protected=20static=20void=20setFacesContextAsCurrentInstance(final=20=
FacesContext=20facesContext)=20{

=09=09=09FacesContext.setCurrentInstance(facesContext);

=09=09}

=09}

=20

=09public=20static=20FacesContext=20getFacesContext(final=20String=20viewI=
d,=20final=20ServletRequest=20request,=20final=20ServletResponse=20respons=
e)=20{=20

=09=09FacesContext=20facesContext=20=3D=20FacesContext.getCurrentInstance(=
);

=09=09if=20(facesContext=20!=3D=20null)=20{=20

=09=09=09return=20facesContext;

=09=09}=20

=09=09return=20getNewFacesContext(viewId,=20request,=20response);

=09}

=20

=09public=20static=20FacesContext=20getNewFacesContext(final=20String=20vi=
ewId,=20final=20ServletRequest=20request,=20final=20ServletResponse=20resp=
onse)=20{

=09=09FacesContext=20facesContext;

=09=09FacesContextFactory=20contextFactory=20=3D=20(FacesContextFactory)=20=
FactoryFinder.getFactory(FactoryFinder.FACES_CONTEXT_FACTORY);

=09=09LifecycleFactory=20lifecycleFactory=20=3D=20(LifecycleFactory)=20Fac=
toryFinder.getFactory(FactoryFinder.LIFECYCLE_FACTORY);

=09=09Lifecycle=20lifecycle=20=3D=20lifecycleFactory.getLifecycle(Lifecycl=
eFactory.DEFAULT_LIFECYCLE);

=09=09facesContext=20=3D=20contextFactory.getFacesContext(((HttpServletReq=
uest)request).getSession().getServletContext(),request,=20response,=20life=
cycle);

=09=09InnerFacesContext.setFacesContextAsCurrentInstance(facesContext);

=09=09UIViewRoot=20view=20=3D=20facesContext.getApplication().getViewHandl=
er().createView(facesContext,=20viewId);

=09=09facesContext.setViewRoot(view);=20

=09=09return=20facesContext;

=09}=20

}

=20

And=20the=20final=20piece=20of=20the=20puzzle=20is=20a=20struts=20action=20=
that=20actually=20loads=20the=20context=20and=20forwards=20to=20the=20appr=
opriate=20JSF=20method...which=20looks=20like=20this:

=20

public=20class=20ForwardToJSFAction=20extends=20Action=20{

=09

=09public=20ActionForward=20execute(ActionMapping=20mapping,=20ActionForm=20=
form,=20HttpServletRequest=20request,=20HttpServletResponse=20response)=20=
throws=20Exception=20{=20

=09=09JSFMapping=20viewMapping=20=3D=20(JSFMapping)=20mapping;

=09=09FacesContext=20ctx=20=3D=20JSFBridge.getFacesContext(viewMapping.get=
ViewId(),=20request,=20response);=20

=09=09MethodBinding=20mb=20=3D=20lookupMethodBinding(viewMapping,=20ctx);=20=


=09=09navigateToMethodBinding(viewMapping,=20ctx,=20mb);

=09=09return=20null;

=09}

=20

=09private=20MethodBinding=20lookupMethodBinding(JSFMapping=20viewMapping,=
=20FacesContext=20ctx)=20{

=09=09return=20ctx.getApplication().createMethodBinding("#{"=20+=20viewMap=
ping.getJsfAction()=20+=20"}",=20new=20Class[]=20{});

=09}

=20

=09private=20void=20navigateToMethodBinding(JSFMapping=20viewMapping,=20Fa=
cesContext=20ctx,=20MethodBinding=20mb)=20{

=09=09Object=20obj=20=3D=20mb.invoke(ctx,=20new=20Object[]=20{});

=09=09NavigationHandler=20navHandler=20=3D=20ctx.getApplication().getNavig=
ationHandler();

=09=09navHandler.handleNavigation(ctx,=20"#{"=20+=20viewMapping.getJsfActi=
on()=20+=20"}",=20(String)=20obj);

=09}

}

=20

Now,=20as=20odd=20as=20all=20this=20looks,=20it=20actually=20works=20quite=
=20well=20in=2099.9%=20of=20the=20cases.=20=20We=20get=20a=20request=20in=20=
struts,=20which=20forwards=20quite=20nicely=20onto=20a=20JSF=20method=20an=
d=20completes=20the=20business=20process=20in=20JSF.=20=20Every=20now=20an=
d=20then=20though,=20we=20get=20the=20following=20error=20when=20we=20try=20=
to=20invoke=20the=20method=20binding:

Caused=20by:=20java.lang.NullPointerException
=09at=20org.apache.catalina.connector.Request.setAttribute(Request.java:13=
76)
=09at=20org.apache.catalina.connector.RequestFacade.setAttribute(RequestFa=
cade.java:500)
=09at=20javax.servlet.ServletRequestWrapper.setAttribute(ServletRequestWra=
pper.java:283)
=09at=20org.apache.myfaces.context.servlet.RequestMap.setAttribute(Request=
Map.java:46)
=09at=20org.apache.myfaces.context.servlet.AbstractAttributeMap.put(Abstra=
ctAttributeMap.java:104)
=09at=20org.apache.myfaces.el.VariableResolverImpl.resolveVariable(Variabl=
eResolverImpl.java:301)
=09at=20org.apache.myfaces.config.LastVariableResolverInChain.resolveVaria=
ble(LastVariableResolverInChain.java:42)
=09at=20org.apache.myfaces.el.ValueBindingImpl$ELVariableResolver.resolveV=
ariable(ValueBindingImpl.java:574)
=09at=20org.apache.commons.el.NamedValue.evaluate(NamedValue.java:124)
=09at=20org.apache.myfaces.el.ValueBindingImpl.resolveToBaseAndProperty(Va=
lueBindingImpl.java:455)
=09at=20org.apache.myfaces.el.MethodBindingImpl.resolveToBaseAndProperty(M=
ethodBindingImpl.java:180)
=09at=20org.apache.myfaces.el.MethodBindingImpl.invoke(MethodBindingImpl.j=
ava:114)
Diving=20into=20Request.java(Line=201376),=20shows=20that=20it's=20happeni=
ng=20on=20this=20line:
Object=20listeners[]=20=3D=20context.getApplicationEventListeners();
So=20I'm=20guessing=20that=20'context'=20is=20null=20for=20some=20reason.=20=
=20Since=20it=20is=20so=20rare,=20it's=20almost=20impossible=20to=20reprod=
uce=20in=20a=20manner=20consistent=20enough=20to=20actually=20diagnose=20a=
nd=20debug=20it.
Can=20anyone=20see,=20from=20the=20above,=20anything=20that=20could=20shed=
=20some=20light=20on=20this?
Cheers
Adam

Number=201=20in=20Truck=20Insurance

______________________________________________________________________
CAUTION=20-=20This=20message=20is=20intended=20for=20the=20addressee=20nam=
ed=20above.

It=20may=20contain=20privileged=20or=20confidential=20information.=20If=20=
you=20are=20
not=20the=20intended=20recipient=20of=20this=20message=20you=20must=20not=20=
use,=20
copy,=20distribute=20or=20disclose=20it=20to=20anyone=20other=20than=20the=
=20addressee.
If=20you=20have=20received=20this=20email=20in=20error=20please=20return=20=
the=20message=20to=20the=20sender=20by=20replying=20to=20it=20and=20then=20=
delete=20the=20message=20from=20your=20computer.

Internet=20e-mails=20are=20not=20necessarily=20secure.=20
National=20Transport=20Insurance=20does=20not=20accept=20responsibility=20=
for=20changes=20made=20to=20this=20message=20after=20it=20was=20sent.
______________________________________________________________________
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