Hi,
I didn't look at the DefaultServlet code at all, there's no need. The post I was
referring to was one from you that said
Try { while { ... } } catch { ... }
Where either ... can throw an exception is the same as
While { ... try { ... } catch { ... } }
And obviously the two are not equal, because the second construct would keep working
the while loop and the first one would abort on the first error. That's a critical
difference. Now you're quoting specific DefaultServlet code, and that's fine, I don't
care to look at it now because it obviously works and I have more important things to
do. But your original message had just an abstract while/try/catch comparison
question, nothing specific to DefaultServlet, and that original message was wrong, and
that's the one I was responding to.
Yoav Shapira http://www.yoavshapira.com
>-----Original Message-----
>From: Steffen Heil [mailto:[EMAIL PROTECTED]
>Sent: Tuesday, October 12, 2004 1:43 PM
>To: 'Tomcat Developers List'
>Subject: AW: DefaultServlet and getOutputStream() / getWriter()
>
>Hi
>
>
>> The rewritten while{} patch you suggested definitely changed behavior
>significantly, as I and others pointed out ;)
>
>Ähm, no.
>Sorry to say that, but I think, you didn't review the code for that
>statement:
>One example taken from DefaultServlet.java, lines 2030 to 2054:
>
> IOException exception = null;
> long bytesToRead = end - start + 1;
>
> char buffer[] = new char[input];
> int len = buffer.length;
> while ( (bytesToRead > 0) && (len >= buffer.length)) {
> try {
> len = reader.read(buffer);
> if (bytesToRead >= len) {
> writer.write(buffer, 0, len);
> bytesToRead -= len;
> } else {
> writer.write(buffer, 0, (int) bytesToRead);
> bytesToRead = 0;
> }
> } catch (IOException e) {
> exception = e;
> len = -1;
> }
> if (len < buffer.length)
> break;
> }
>
> return exception;
>
>THIS IS EQUAL TO:
>
> IOException exception = null;
> long bytesToRead = end - start + 1;
>
> char buffer[] = new char[input];
> int len = buffer.length;
> try {
> while ( (bytesToRead > 0) && (len >= buffer.length)) {
> len = reader.read(buffer);
> if (bytesToRead >= len) {
> writer.write(buffer, 0, len);
> bytesToRead -= len;
> } else {
> writer.write(buffer, 0, (int) bytesToRead);
> bytesToRead = 0;
> }
> if (len < buffer.length)
> break;
> }
> } catch (IOException e) {
> exception = e;
> len = -1;
> }
>
> return exception;
>
>OR EVEN:
>
> long bytesToRead = end - start + 1;
>
> char buffer[] = new char[input];
> int len = buffer.length;
> try {
> while ( (bytesToRead > 0) && (len >= buffer.length)) {
> len = reader.read(buffer);
> if (bytesToRead >= len) {
> writer.write(buffer, 0, len);
> bytesToRead -= len;
> } else {
> writer.write(buffer, 0, (int) bytesToRead);
> bytesToRead = 0;
> }
> }
> return null;
> } catch (IOException e) {
> return e;
> }
>
>I am very sure about this.
>And I also do NOT understand, why the exception is reported as result and
>not really thrown.
>The caller always uses:
>
> IOException exception = null;
>
> while ( (exception == null) && (ranges.hasMoreElements()) ) {
>
> ....
> exception = copyRange(istream, ostream, currentRange.start,
> currentRange.end);
> ...
>
> }
>
> ostream.println();
> ostream.print("--" + mimeSeparation + "--");
>
> // Rethrow any exception that has occurred
> if (exception != null)
> throw exception;
>
>Whereas it would absolutely make more sense to me NOT to catch the
>Exception
>but rather use:
>
> try {
> while ( ranges.hasMoreElements() ) {
>
> ....
> copyRange(istream, ostream, currentRange.start,
> currentRange.end);
> ...
>
> }
> } finally {
> // if nessesary, put code to ensure istream is closed here.
> ostream.println();
> ostream.print("--" + mimeSeparation + "--");
> }
>
>This is what try-finally is all about, isn't it?
>
>
>I agree, that I am new to this and I might be wrong, but this leads me back
>right to where I started. Whom to ask to understand the existing code?
>
>
>> When you're looking at the code, keep in mind that Tomcat's
>DefaultServlet
>(like virtually every other Tomcat component) can be extended or wrapped.
>Such wrappers or extenders could call getWriter first.
>
>Ok, I forgot about includes and such.
>
>> I'm happy you're looking at the code. If I were in your position (and I
>definitely was, although that seems long ago now ;)), I would look instead
>at Bugzilla, take a bug, and try to fix it.
>
>I will propably do this some time soon. However, right now I am evaluating
>the Default Servlet code because I need to build my customized one and I
>thought a lot of work is already done. Not trying to reinvent the wheel
>though. That's why I am staring at DefaultServlet.java only right now.
>
>Regards,
> Steffen
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