Well bs chuck and laughing dave
I ran your exact example / deleted FunkyImage.jpg and got this on screen
java.lang.NullPointerException
coreservlets.ImageFile.doGet(ImageFile.java:34)
javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
**********But wait a minute Im NOT supposed to get NullPointerException
!!!!!***********
public class ImageFile extends HttpServlet
{
public void doGet( HttpServletRequest rq, HttpServletResponse rp ) throws
ServletException, IOException
// public static void main(String[] args)
{
// javax.servlet.http.HttpServletResponse rp;
// javax.servlet.http.HttpServletRequest rq;
ServletContext sc;
rp.setContentType( "image/jpeg" );
sc = getServletContext ();
InputStream in = sc.getResourceAsStream("FunkyImage.JPG");
int r = 0;
byte[] by = new byte[4096];
OutputStream os = rp.getOutputStream();
if (in==null) System.out.println("This is when in == null");
while( ( r = in.read(by)) != -1)
{
if (in==null) System.out.println("This is when in == null");
os.write(by, 0, r);
}
os.flush();
os.close() ;
} //DoGet
} //ImageFile
How is it that (in==null) didnt evaluate true ?
Comments?
M-
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----- Original Message -----
From: "david.delbecq" <[EMAIL PROTECTED]>
To: "Tomcat Users List" <users@tomcat.apache.org>
Sent: Monday, November 13, 2006 4:03 PM
Subject: Re: How do I ........?
> o.O
>
> .............
> .............
> (not laughing, not laughing, not laughing)
>
> this is going to be my funniest evening in the week, and yet it still
> monday!
>
>
> Martin Gainty a écrit :
>> the instant you execute code where a variable is NULL you will throw
> NullPointerException
>
> Change your books! Here are the conditions in which
> NullPointerExceptions can be thrown (can be found in sun's javadocs)
>
> Thrown when an application attempts to use |null| in a case where an
> object is required. These include:
>
> * Calling the instance method of a |null| object.
> * Accessing or modifying the field of a |null| object.
> * Taking the length of |null| as if it were an array.
> * Accessing or modifying the slots of |null| as if it were an array.
> * Throwing |null| as if it were a |Throwable| value.
>
> Applications should throw instances of this class to indicate other
> illegal uses of the |null| object.
>
>
> (notice the use of the term *required*)
>
>> if you want robust code you are better off wrapping in try catch block
> as in
>> try
>> {
>> if( in == null) System.out.println("This statement will never be
> executed as NullPointerException will be thrown");
>> }
>> catch(NullPointerException npe)
>> {
>> System.out.println("variable in has thrown NullPointerException so
> something about that here");
>> }
>
> Did you actually *tried* that code?
>
>>
>> This e-mail communication and any attachments may contain confidential
> and privileged information for the use of the
>> designated recipients named above. If you are not the intended
> recipient, you are hereby notified that you have received
>> this communication in error and that any review, disclosure,
> dissemination, distribution or copying of it or its
>> contents
>> ----- Original Message -----
>> From: "Christopher Schultz" <[EMAIL PROTECTED]>
>> To: "Tomcat Users List" <users@tomcat.apache.org>
>> Sent: Monday, November 13, 2006 2:57 PM
>> Subject: Re: How do I ........?
>>
>>
>> Steve,
>>
>> Steve R Burrus wrote:
>> >>> hi chris this is steve Burrus and the line of code in question is the
>> >>> while loop : "while( ( r = in.read(by)) != -1) {" the server error
>> for a
>> >>> long time has always pointed to that line of code creating the NPE.
>> Yup, that's the first time you use the InputStream after attempting to
>> load your file. It's pretty simple to check for null: just use the code
>> I suggested in my last message:
>>
>> >>>> Correct me if I'm wrong, but this generally checks for null:
>> >>>>
>> >>>> if(null == in)
>> >>>> // handle the null condition
>> Now, it's up to you what you want to do in the event of a NULL image.
>> You could either return a "404 Not Found" error status, or return a
>> known good image that actually says "ERROR" on it.
>>
>> -chris
>>
>>>
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>>>
>>>
>
> Mouhahahahaha. (sorry, couldn't hold it)
>
>
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