On Thu, 15 Mar 2001, Daniel Lynn wrote:
Hello,
Try this:
String foo = (request.getParameter("foo") != null) ?
request.getParameter("foo") : "";
// Now variable foo is NOT null
if (foo.equals("foobar")) {}
or maybe:
String bar = request.getParameter("bar");
// if bar == null, the equals() method is never called!
if (bar != null && bar.equals("bar")) {}
HTH,
Kare
> ok, I got 2 responses voting for checking if the cariale is equal to null or use
> the equals() function... maybe it's something wierd wih Resin, but if I say
>
> if (request.getParameter("test")==null)
>
> or
>
> if (request.getParameter("test").equals("blah"))
>
> and test was never passed instead of the conditional just returning false I get a
> NullPointerException.
>
> -Daniel
>
> christopher brown wrote:
>
> > isset() is generally useful in PHP because it's a loosely-typed language
> > that doesn't require variable declarations. In Java, you can avoid a lot of
> > these issues because the compiler picks up situations where you try to use a
> > variable without declaring it beforehand, or if it's likely to have been
> > unassigned a value. For example:
> >
> > String s;
> > if (some-conditional-test) s = "hello";
> > System.out.println(s);
> >
> > ...should be picked up by the compiler.
> >
> > In a lot of other cases, you can often avoid returning null by returning
> > empty arrays or collections in Java. In many others, you can also carefully
> > arrange expressions, such as:
> >
> > if ("something".equals(request.getParameter("abc"))) ...;
> >
> > This is good practice in any case, as even if there's no such parameter
> > "abc", you'll always avoid a NullPointerException.
> >
> > Hint (OT): with PHP, or other loosely-typed languages such as JavaScript,
> > try forcing types correctly by using literals before variables in
> > expressions. Instead of:
> > if (x > 0) ...
> > Write:
> > if (0 < x)
> >
> > Back on topic, in all other cases, what's wrong with using try...catch to
> > handle NullPointerExceptions ? It's arguably much cleaner than mixing in
> > "if (isset($x))" throughout your code. You can arrange the normal flow of
> > execution, assuming everything goes well, within a try...catch block. If
> > exceptionnally something is null, handle this elsewhere. And if that
> > doesn't suit, just try:
> >
> > if (null == mavariable) ...;
> >
> > Hope this helps!
> > -Christopher Brown
> >
> > ----- Original Message -----
> > From: "Daniel Lynn" <[EMAIL PROTECTED]>
> > To: <[EMAIL PROTECTED]>
> > Sent: Thursday, March 15, 2001 6:23 AM
> > Subject: isset()
> >
> > > ok, in PHP there is a command called isset(). It returns a boolean to
> > > tell you if a certain variable was passed to the program or not. (Helps
> > > eliminate those nullpointer exceptions without putting everything in
> > > try/catch statements) Now, I was looking for one in JSP and I'm having a
> > > little trouble. I think it may just be I don't know what I'm looking
> > > for, so if anyone would be so kind as to let me know the name of the
> > > function if it exists it'd be MUCH appreciated. Thank you in advance.
> > >
> > > -Daniel
> > >
> > >
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> Some relevant FAQs on JSP/Servlets can be found at:
>
> http://java.sun.com/products/jsp/faq.html
> http://www.esperanto.org.nz/jsp/jspfaq.html
> http://www.jguru.com/jguru/faq/faqpage.jsp?name=JSP
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>
--
Kare Nuorteva
http://www.kare.uklinux.net/
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Some relevant FAQs on JSP/Servlets can be found at:
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http://www.esperanto.org.nz/jsp/jspfaq.html
http://www.jguru.com/jguru/faq/faqpage.jsp?name=JSP
http://www.jguru.com/jguru/faq/faqpage.jsp?name=Servlets
