Christopher Schultz wrote:
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Konstantin,
On 12/22/13, 8:54 AM, Konstantin Preißer wrote:
Note that the reason for a EOFException is slightly different than
just reading from a stream when there is no more data present.
In Java (and .Net), when you read from a Stream which is finished
(there is no more data present), read() returns -1. Even when you
repeatedly call read(), you will still get -1, but no exception.
Normally you do just while ((read = input.read(buffer)) > 0) {
...} to test for the end of stream/data.
It's important to note for beginners that you want the comparison
operator to be ">=" and not just ">". If you use "0" than you run the
risk of attempting to read from a stream that has stalled and getting
zero bytes (and stopping) when there may future bytes on the stream.
So it seems that contrarily to what I was writing earlier, the EOFexception is thus not an
indication of something wrong in the logic.
After consulting the relevant Javadocs (which I should probably have done before writing
nonsense, mea culpa), I am nevertheless under the impression that there are some
inconsistencies in terms of what one could be expecting (in terms of exceptions) when
reading the HttpRequest input stream. The basic thing seems to be :
- if read() returns n > 0, then you have actually read something
- if read() returns n = 0, you have not read anything, but there was no error and there
was no "end of file" condition. (This should only happen when you are reading from
something in non-blocking mode, though.)
- if read() returns n = -1, then you do not have an error, but you have reached the
end-of-file; and if you read() again, you'll keep getting -1.
- if you get an exception, the basic thing seems to be an IOexception, but then it depends
of the actual sub-class which you are using for the stream, which can redefine this.
And considering how it happens, the EOFexception seems to be really misnamed, because it
is /anything but/ an EOF condition.
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