Re: do you get error in this url?
maya wrote:
this is code:
String sBrowser = "";
......
sBrowser = request.getHeader("user-agent");
if (sBrowser.indexOf("Gecko") != -1)
sBrowser = "mozilla";
else sBrowser = "ie";
this, specif., was line causing error (acc. to log):
if (sBrowser.indexOf("Gecko") != -1)
(but still not sure WHAT prob is w/this line..)
...
but how can there be no user-agent? request.getHeader("user-agent") is
a standard method in servlet API to get what browser is being used; I
don't get this.
Mayeul explained this. The method is server side; it can only report
what is sent to it. The header is client side; the server does not
return what, if anything, is sent.
All you had to do was read the Javadocs for
HttpServletRequest#getHeader(String):
"Returns: a String containing the value of the requested header, or
null if the request does not have a header of that name."
This alerts you to the possibility that this "standard method" has
'null' as a "standard" return value, and this obligates you to deal
with that possibility, an obligation your code shirked and thus
engendered a bug.
Request headers are an external input to your program. Your program
does not control external inputs. You must deal with every possible
input from the outside, including no input at all. You cannot assume
just because the well-documented possibility of a 'null' return seems
strange to you that that relieves you of responsibility for it. You
must be familiar with the standard documentation for "standard"
methods. Your code must deal with all possible inputs.
--
Lew