AW: WG: Question: Can not get access to object fields (Null Pointer Exception) pls pls help!
hey, lot of thanks,
the state field was really null because the parameters were passed to the
constructor but I never saved the value...
By the reason I am a novice in tapestry, I had searched it everywhere but
not in that simple way...
Greetings,
Michael Wölm
-Ursprüngliche Nachricht-
Von: Steve Shucker [mailto:[EMAIL PROTECTED]
Gesendet: Dienstag, 12. September 2006 16:03
An: Tapestry users
Betreff: Re: WG: Question: Can not get access to object fields (Null Pointer
Exception) pls pls help!
As a general rule, it's safer to put the literal first in statements
like this:
"admin".equals(user.getState())
If anyone wants to say that it looks/reads a bit funny, I'll agree.
It's an odd syntax, but it protects you from NPEs.
-Steve
Martin Strand wrote:
> Well, if you get a NPE on this line:
>
>>> user.getState().equals("admin")
>>>
> then either "user" or "getState()" is null, right?
> And, since "user" is definitely not null, your private String "state" is
obviously null.
>
> Perhaps you should add something like this:
>
>>> private String state = "initial state";
>>>
>
>
> Martin
>
> On Tue, 12 Sep 2006 15:52:25 +0200, Michael Wölm <[EMAIL PROTECTED]> wrote:
>
>
>> Hi,
>>
>> Sadly, nobody have helped me with my problem. I dont know why. Am I too
noob
>> or is my question incomprehensible? I would be pleased, if anybody could
>> give me an advice for my problem.
>>
>> Greettings from Germany,
>> Michael Wölm
>>
>> Original message is under this.
>>
>> -Ursprüngliche Nachricht-
>> Von: m-woelm [mailto:[EMAIL PROTECTED]
>> Gesendet: Sonntag, 10. September 2006 16:13
>> An: 'Tapestry users'
>> Betreff: Question: Can not get access to object fields (Null Pointer
>> Exception)
>>
>> Hi,
>>
>> I hope anybody could explain me why I get a Null Pointer Exception, if I
>> want to get access to a field of an object. My method is similar to the
>> eshop-project of the book Enjoying web dev with Tapestry.
>>
>> I tried to change the Listener-method onLogin as follows:
>>
>> public void onLogin(IRequestCycle cycle) {
>>
>> try {
>>
>> User user =
Users.getKnownUsers().getUser(email,password);
>>
>> getUser().copyFrom(user);
>>
>> if (user.getState().equals("admin"))
>> cycle.activate("Admin_Konsole");
>>
>> else cycle.activate("User_Konsole");
>>
>> } catch (AuthenticationException e) {
>>
>> ValidationDelegate delegate = getDelegate();
>>
>> delegate.setFormComponent(null);
>>
>> delegate.record("Login failed", null);
>>
>> }
>>
>> }
>>
>>
>> Now I get an exception at point (user.getState().equals(admin)).
>>
>> But why? user was set to the login-user two lines before? Why I cant get
>> the field: private String state which I have set in User.class:
>>
>>
>> private String state;
>>
>> public String getState() {
>>
>> return this.state;
>>
>> }
>>
>>
>> Thx ahead!
>>
>> Michael Wölm
>>
>>
>> <mailto:[EMAIL PROTECTED]> [EMAIL PROTECTED]
>>
>> Public Key: <http://gsg.ath.cx/~phoenix/downloads/MyPublicKey.asc>
>> href="http://gsg.ath.cx/~phoenix/downloads/MyPublicKey.asc
>>
>>
>>
>>
>>
>> -
>> To unsubscribe, e-mail: [EMAIL PROTECTED]
>> For additional commands, e-mail: [EMAIL PROTECTED]
>>
>>
>>
>
>
>
> -
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>
>
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Re: WG: Question: Can not get access to object fields (Null Pointer Exception) pls pls help!
As a general rule, it's safer to put the literal first in statements
like this:
"admin".equals(user.getState())
If anyone wants to say that it looks/reads a bit funny, I'll agree.
It's an odd syntax, but it protects you from NPEs.
-Steve
Martin Strand wrote:
Well, if you get a NPE on this line:
user.getState().equals("admin")
then either "user" or "getState()" is null, right?
And, since "user" is definitely not null, your private String "state" is
obviously null.
Perhaps you should add something like this:
private String state = "initial state";
Martin
On Tue, 12 Sep 2006 15:52:25 +0200, Michael Wölm <[EMAIL PROTECTED]> wrote:
Hi,
Sadly, nobody have helped me with my problem. I dont know why. Am I too noob
or is my question incomprehensible? I would be pleased, if anybody could
give me an advice for my problem.
Greettings from Germany,
Michael Wölm
Original message is under this.
-Ursprüngliche Nachricht-
Von: m-woelm [mailto:[EMAIL PROTECTED]
Gesendet: Sonntag, 10. September 2006 16:13
An: 'Tapestry users'
Betreff: Question: Can not get access to object fields (Null Pointer
Exception)
Hi,
I hope anybody could explain me why I get a Null Pointer Exception, if I
want to get access to a field of an object. My method is similar to the
eshop-project of the book “Enjoying web dev with Tapestry”.
I tried to change the Listener-method onLogin as follows:
public void onLogin(IRequestCycle cycle) {
try {
User user = Users.getKnownUsers().getUser(email,password);
getUser().copyFrom(user);
if (user.getState().equals("admin"))
cycle.activate("Admin_Konsole");
else cycle.activate("User_Konsole");
} catch (AuthenticationException e) {
ValidationDelegate delegate = getDelegate();
delegate.setFormComponent(null);
delegate.record("Login failed", null);
}
}
Now I get an exception at point (user.getState().equals(“admin”)).
But why? user was set to the login-user two lines before? Why I can’t get
the field: private String state which I have set in User.class:
private String state;
public String getState() {
return this.state;
}
Thx ahead!
Michael Wölm
[EMAIL PROTECTED]
Public Key:
href="http://gsg.ath.cx/~phoenix/downloads/MyPublicKey.asc
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
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To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
Re: WG: Question: Can not get access to object fields (Null Pointer Exception) pls pls help!
Well, if you get a NPE on this line:
>> user.getState().equals("admin")
then either "user" or "getState()" is null, right?
And, since "user" is definitely not null, your private String "state" is
obviously null.
Perhaps you should add something like this:
>> private String state = "initial state";
Martin
On Tue, 12 Sep 2006 15:52:25 +0200, Michael Wölm <[EMAIL PROTECTED]> wrote:
> Hi,
>
> Sadly, nobody have helped me with my problem. I dont know why. Am I too noob
> or is my question incomprehensible? I would be pleased, if anybody could
> give me an advice for my problem.
>
> Greettings from Germany,
> Michael Wölm
>
> Original message is under this.
>
> -Ursprüngliche Nachricht-
> Von: m-woelm [mailto:[EMAIL PROTECTED]
> Gesendet: Sonntag, 10. September 2006 16:13
> An: 'Tapestry users'
> Betreff: Question: Can not get access to object fields (Null Pointer
> Exception)
>
> Hi,
>
> I hope anybody could explain me why I get a Null Pointer Exception, if I
> want to get access to a field of an object. My method is similar to the
> eshop-project of the book “Enjoying web dev with Tapestry”.
>
> I tried to change the Listener-method onLogin as follows:
>
>public void onLogin(IRequestCycle cycle) {
>
> try {
>
> User user = Users.getKnownUsers().getUser(email,password);
>
> getUser().copyFrom(user);
>
> if (user.getState().equals("admin"))
> cycle.activate("Admin_Konsole");
>
> else cycle.activate("User_Konsole");
>
> } catch (AuthenticationException e) {
>
> ValidationDelegate delegate = getDelegate();
>
> delegate.setFormComponent(null);
>
> delegate.record("Login failed", null);
>
> }
>
> }
>
>
> Now I get an exception at point (user.getState().equals(“admin”)).
>
> But why? user was set to the login-user two lines before? Why I can’t get
> the field: private String state which I have set in User.class:
>
>
> private String state;
>
> public String getState() {
>
> return this.state;
>
> }
>
>
> Thx ahead!
>
> Michael Wölm
>
>
> [EMAIL PROTECTED]
>
> Public Key:
> href="http://gsg.ath.cx/~phoenix/downloads/MyPublicKey.asc
>
>
>
>
>
> -
> To unsubscribe, e-mail: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
>
>
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
WG: Question: Can not get access to object fields (Null Pointer Exception) pls pls help!
Hi,
Sadly, nobody have helped me with my problem. I dont know why. Am I too noob
or is my question incomprehensible? I would be pleased, if anybody could
give me an advice for my problem.
Greettings from Germany,
Michael Wölm
Original message is under this.
-Ursprüngliche Nachricht-
Von: m-woelm [mailto:[EMAIL PROTECTED]
Gesendet: Sonntag, 10. September 2006 16:13
An: 'Tapestry users'
Betreff: Question: Can not get access to object fields (Null Pointer
Exception)
Hi,
I hope anybody could explain me why I get a Null Pointer Exception, if I
want to get access to a field of an object. My method is similar to the
eshop-project of the book Enjoying web dev with Tapestry.
I tried to change the Listener-method onLogin as follows:
public void onLogin(IRequestCycle cycle) {
try {
User user = Users.getKnownUsers().getUser(email,password);
getUser().copyFrom(user);
if (user.getState().equals("admin"))
cycle.activate("Admin_Konsole");
else cycle.activate("User_Konsole");
} catch (AuthenticationException e) {
ValidationDelegate delegate = getDelegate();
delegate.setFormComponent(null);
delegate.record("Login failed", null);
}
}
Now I get an exception at point (user.getState().equals(admin)).
But why? user was set to the login-user two lines before? Why I cant get
the field: private String state which I have set in User.class:
private String state;
public String getState() {
return this.state;
}
Thx ahead!
Michael Wölm
[EMAIL PROTECTED]
Public Key:
href="http://gsg.ath.cx/~phoenix/downloads/MyPublicKey.asc
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
