WG: Question: Can not get access to object fields (Null Pointer Exception) pls pls help!

2006-09-12 Thread Michael Wölm 
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

 

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Re: WG: Question: Can not get access to object fields (Null Pointer Exception) pls pls help!

2006-09-12 Thread Martin Strand 
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


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Re: WG: Question: Can not get access to object fields (Null Pointer Exception) pls pls help!

2006-09-12 Thread Steve Shucker 
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


 mailto:[EMAIL PROTECTED] [EMAIL PROTECTED]

Public Key:  http://gsg.ath.cx/~phoenix/downloads/MyPublicKey.asc
href=http://gsg.ath.cx/~phoenix/downloads/MyPublicKey.asc





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AW: WG: Question: Can not get access to object fields (Null Pointer Exception) pls pls help!

2006-09-12 Thread m-woelm 
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 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


  mailto:[EMAIL PROTECTED] [EMAIL PROTECTED]

 Public Key:  http://gsg.ath.cx/~phoenix/downloads/MyPublicKey.asc
 href=http://gsg.ath.cx/~phoenix/downloads/MyPublicKey.asc





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