[jdom-interest] NoSuch*Exceptions in JDOM

[Andre Van Delft]

You misinterpreted my example.
There is nothing wrong with

      str += jnl.getChild("JTL").getContent();

since this uses the exception throwing getChild,
so no NullPointerException can occur.

Getting the other child uses my util function
that may return null; it has a null test:
      org.jdom.Element sbt   = getChild(jnl, "SBT");
      if (sbt != null) str += sbt.getContent();
Nothing can go wrong here.

Please note the line:
      // DTD: jnl = jtl,sbt?,...
I meant to say that a JNL contains a JTL and an optional SBT.
Therefore the JTL and SBT children are fetched differently.

Jason Hunter wrote:

> Andre, your example shows exactly what's wrong with returning null from
> getChild()!  Notice how you're calling jnl.getChild("JTL").getContent()
> without doing a null check.  Well, sometime it's going to happen that
> <JTL/> isn't going to be there, and your only error message is going to
> be a cryptic NullPointerException.  That's the reason we chose to throw
> exceptions in the first place; because Brett and I were both tired of
> tracking down NPEs, especially in already released code because this is
> the sort of thing that happens when the end user does something crazy to
> their XML that you didn't anticipate.
>
> -jh-
>
> Andre Van Delft wrote:
> >
> > I am developing a program that transforms XML into HTML, using JDOM and ECS.
> > A typical code snippet is:
> >
> >   String str = "";
> >   try {
> >      // DTD: jnl = jtl,sbt?,...
> >      str += jnl.getChild("JTL").getContent();
> >      org.jdom.Element sbt   = getChild(jnl, "SBT");
> >      if (sbt != null) str += sbt.getContent();
> >      ...;
> >   }
> >   catch (NoSuchElementException e)
> >   {
> >      handle (target, e);
> >   }
> >
> > Here getChild(jnl, "SBT") is a call to my util function
> > that returns null instead of throwing an exception.
> > The null test is exactly what I want for an optional element.
> > The catch clause is only handling real exceptions.
> > Without my util function, the code would be far more
> > complicated:
> >
> >   String str = "";
> >   try {
> >      // DTD: jnl = jtl,sbt?,...
> >      str += jnl.getChild("JTL").getContent();
> >      try {
> >         str += jnl.getChild("SBT").getContent();
> >      }
> >      catch (NoSuchElementException e)
> >      {
> >           // nothing to do; is OK
> >      }
> >      ...;
> >   }
> >   catch (NoSuchElementException e)
> >   {
> >      handle (target, e);
> >   }
> >
> > IMHO: instead of everybody making his own util functions,
> > JDOM should provide the desired function variations.
> >
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