Hello,
I investigated the topic of byte-range-serving from the DefaultServlet with Acrobat 6.
I noticed that Tomcat 4.1.30 did not any byte-range-serving with Acrobat 6.0.0. The
entire file was sent instead.
I compared the HTTP communication with that of Internet Information server where
byte-range-serving of PDF files works.
Here are my results:
1. HTTP header
Acrobat does not request byte-ranges unless the server sends the header
"Accept-Ranges: bytes". Once I added this header, Acrobat requested byte-ranges.
>From the HTTP 1.1 spec I read that sending this header is not required, but Acrobat
>seems to need it.
2. blanks in multi-byte-range-requests
After having added the header above, Acrobat sent byte-range-requests. But Acrobat
choked.
I did a packet filtering and recognized the following status code sent by Tomcat "416
request range not satisfiable".
The reason was that Acrobat sent multi-byte-range-request using e.g. the following
string
"1000-2000, 3000-3010"
Notice the blank character. It leads to a parsing exception in line 1300 of the
DefaultServlet (Tomcat 4.1.30). If you do a trim() on the rangeDefinition obtained
there, this error does not occur.
3. newline before Mime-separator-string
After fixing step 2 Acrobat did not choke anymore. However, the pdf file was still
served entirely.
Further comparison with the IIS communication revealed that ISS writes the
mime-separation-string ("CATALINA_MIME_BOUNDARY" for Tomcat) on a line line, whereas
Tomcat does not. After prefixing the println-commands with "\n" (lines 1910, 1930,
1964, 1984), it finally worked.
I wonder if you would consider to change the DefaultServlet. IMO Acrobat is a very
important application, and unless it doesn't explicitly violate the HTTP spec Tomcat
should support it.
Best regards
Michael
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