NullPointerException but why?

Question

I have class where

    @Enumerated(EnumType.STRING)
private StateOfDispatchToWD stateOfDispatchToWD = StateOfDispatchToWD.NONE;

And getter and setter:

public StateOfDispatchToWD getStateOfDispatchToWD() {
    return stateOfDispatchToWD;
}

public void setStateOfDispatchToWD(StateOfDispatchToWD stateOfDispatchToWD) {
    this.stateOfDispatchToWD = stateOfDispatchToWD;
}

and method:

public boolean isSuccessfullySentToWD() {
    return zoj.getStateOfDispatchToWD() == StateOfDispatchToWD.SUCCESSFULLY_DISPATCH;
}

and call it from JSF:

            <p:outputLabel value="OK"
                           rendered="#{Z.isSuccessfullySentToWD()}"/>

and sometimes I get:

[javax.enterprise.resource.webcontainer.jsf.lifecycle]
javax.el.ELException: //content/resources/zo.xhtml @240,92 rendered="#{Z.isSuccessfullySentToWD()}":
java.lang.NullPointerException:
javax.faces.FacesException:
javax.el.ELException: //content/resources/zo.xhtml @240,92 rendered="#{Z.isSuccessfullySentToWD()}":
java.lang.NullPointerException

but why? I'm afraid I don't understand. Thanks a lot.

Exception is on line " return zoj.getStateOfDispatchToWD() == StateOfDispatchToWD.SUCCESSFULLY_DISPATCH; " — Martin Hofman, Jun 17 '22 at 07:49
No it isn't, Read the stack trace. It is in the EL, in the expression `#{Z.isSuccessfullySentToWD()}`. There is nothing to suggest you got any further. — user207421, Jun 17 '22 at 08:03
Duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — user207421, Jun 17 '22 at 08:04
Can't tell if this is a duplicate without more information. Please provide a runnable example - specifically show exactly how `zoj` is initialized. — Adam Waldenberg, Jun 17 '22 at 21:25

EffectiveIvana · Answer 1 · 2022-06-17T10:27:49.850

0

Probably the scope of Z is wrong, try to put it in session or application scope

edited Jun 17 '22 at 10:27

answered Jun 17 '22 at 10:27

EffectiveIvana

18
4

It can be if it is in request scope and request is expired, or even if it is in session scope and session is expired – EffectiveIvana Jun 17 '22 at 10:30
Z is @ViewScoped (javax.faces.view) – Martin Hofman Jun 17 '22 at 10:32
And I use it in too: – Martin Hofman Jun 17 '22 at 10:35
Hmm, than what is zoj object? maybe you need to change it with this. – EffectiveIvana Jun 17 '22 at 10:37
Do you have this annotation on top of you managed bean: @Named(value = "Z") or your managed bean is calles Z? – EffectiveIvana Jun 17 '22 at 10:38
I use @Named, and name is Z – Martin Hofman Jun 17 '22 at 10:41
what is zoj object? maybe you need to change it with this -> return this.getStateOfDispatchToWD() == StateOfDispatchToWD.SUCCESSFULLY_DISPATCH; – EffectiveIvana Jun 17 '22 at 10:42
zoj is entity/model – Martin Hofman Jun 17 '22 at 10:43
But what, is it proprety or you reffered to the Z object ? – EffectiveIvana Jun 17 '22 at 10:44
Z is ViewScoped, and Zoj is variable in Z – Martin Hofman Jun 17 '22 at 10:46
and Zoj have variable @Enumerated(EnumType.STRING) private StateOfDispatchToWD stateOfDispatchToWD = StateOfDispatchToWD.NONE; – Martin Hofman Jun 17 '22 at 10:46
how did you initializate zoj in Z? – EffectiveIvana Jun 17 '22 at 10:49
You need to initializate Zoj in default contructor of Z or immedietly like Zoj zoj=new Zoj(); – EffectiveIvana Jun 17 '22 at 10:50
private ZOJ zoj; public ZOJ getZoj() { return zoj; } public void setZoj(ZOJ zoj) { this.zoj = zoj; } and in init I call public void setDocument(ZOJ document) { setZoj(document); } – Martin Hofman Jun 17 '22 at 10:54
First thing, check if your init is even ever called and also init needs to be called in default contrcutor because it is not you who create Z object in view scope – EffectiveIvana Jun 17 '22 at 10:57
Do you maybe use spring or you using JEE? – EffectiveIvana Jun 17 '22 at 10:59
use Jakarta - JEE – Martin Hofman Jun 17 '22 at 11:00
check if your init is even ever called and also init needs to be called in default contrcutor because it is not you who create Z object in view scope – EffectiveIvana Jun 17 '22 at 11:02
Is called, when I open the view and are loaded data from DB to Zoj – Martin Hofman Jun 17 '22 at 11:04
I think that the best is to call init in default contrcutor of Z so you will not have the problem, bacause loading data from DB takes to long and you view is already initialized and because you zoj is still null – EffectiveIvana Jun 17 '22 at 11:08

NullPointerException but why?

1 Answers1