think about NullPointerException as a dereferencing exception. you get one of these /only/ when you try to actually /use/ a reference that is null but cannot be. this, in general, means that the vm or native code of some kind is being asked to /do/ something with a null reference.
http://java.sun.com/j2se/1.4.2/docs/api/java/lang/NullPointerException.html it's important to understand the comment at the bottom of this javadoc, where it says: "Applications should throw instances of this class to indicate other illegal uses of the null object" the key word here is "uses". it is not illegal to /use/ the null object as a parameter to a method. therefore, passing null in itself should never result in a NullPointerException. it's only when the null object is /used/ (dereferenced in some way) that the NPE should be thrown. On Fri, 7 Jan 2005, Jonathan Locke wrote: > > we should not be throwing NullPointerExceptions. the right JDK exception > for this would be IllegalArgumentException. only the VM should throw > NullPointerExceptions. > > On Fri, 7 Jan 2005, Juergen Donnerstag wrote: > > > This is the original code, which did work: class PropertyModel > > > > public PropertyModel(final IModel model, final String expression, > > boolean applyFormatting) > > { > > super(null); > > > > if (model == null) > > { > > throw new NullPointerException("Parameter 'model' must not be > > null"); > > } > > > > this.model = model; > > this.expression = expression; > > this.applyFormatting = applyFormatting; > > } > > > > and this is the new one > > > > public PropertyModel(final IModel model, final String expression) > > { > > super(null); > > > > checkModelNotNull(model); > > > > this.model = model; > > this.expression = expression; > > > > ApplicationSettings settings = > > RequestCycle.get().getApplication().getSettings(); > > this.applyFormatting = > > settings.isPropertyModelDefaultApplyFormatting(); > > } > > > > > > NPE is thrown because RequestCycle.get() returns null. The > > RequestCycle has not yet been initialized. Though it may be a problem > > of our unit tests only, I'd still suggest to fix it. > > > > Juergen > > > > > > On Fri, 7 Jan 2005 20:24:01 +0100, Juergen Donnerstag > > <[EMAIL PROTECTED]> wrote: > > > Hi, > > > > > > after modifying the MarkupParser javadoc (and committing it), run > > > maven jar on wicket core and I was surprised that it failed. I thought > > > I made the mistake while changeing the javadoc, but after debugging > > > the problem I not sure. The problem is that RequesrCycle.get() returns > > > null and throws a NPE in cases where it didn't happen before. Any idea > > > what about cause? > > > > > > Juergen > > > > > > > > > ------------------------------------------------------- > > The SF.Net email is sponsored by: Beat the post-holiday blues > > Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. > > It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt > > _______________________________________________ > > Wicket-develop mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/wicket-develop > > > > > > ------------------------------------------------------- > The SF.Net email is sponsored by: Beat the post-holiday blues > Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. > It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt > _______________________________________________ > Wicket-develop mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/wicket-develop > ------------------------------------------------------- The SF.Net email is sponsored by: Beat the post-holiday blues Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt _______________________________________________ Wicket-develop mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/wicket-develop
