web server - Borland Technical Publications

Large data transfer
Downloading large data
The following modes are available for downloading large data from the Borland web
container to the browser:
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■
Chunked download
Non-chunked download
Implementing chunked download
In the chunked download mode, the Borland web container does not wait until it has all
the data to send. As soon as servlet generates the data, the web container starts
sending the data to the browser via Apache in fixed size buffers.
Because the data is flushed as soon as it is available, the chunked download mode of
transfer has low memory requirements both on Apache and the Borland web container.
The browser user sees data as it arrives rather than as one large lump at the end of the
full transfer.
Enabling chunked download
To enable chunked download mode, you update the Borland web container server.xml
file which is stored in your Partition's data directory:
adm/tomcat/conf/
For more information, go to Chapter 4, “Web components.”
To enable the chunked download:
1 In the Borland web container server.xml, locate the section of
the code.
2 For the IIOP service you want to enable chunked download, set
enableChunking="true"
3 By default, the download buffer size is set to 4096. To change it for an IIOP service,
use the downloadBufferSize attribute as follows:
downloadBufferSize=
Where is a numeric value >0.
Note If an invalid value is presented (non numeric/negative number) then the default 4096
value is employed.
The chunked download mode of transfer has an overhead of an extra thread per each
request.
Known content length versus unknown
Based on whether content length is known in advance or not, chunked download mode
can take one of the following two paths:
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■
chunked download with known content length
chunked download with unknown content length
Chunked download with known content length
In this case, a servlet or JSP knows the content length of the data in advance of the
transfer. The servlet sets the Content-Length HTTP header before writing out the data.
The Borland web container writes out a single response header followed by multiple
chunks of data. Apache receives this from the web container and sends data in the
same fashion to the browser.
The response header contains the following header:
Content-Length=
48 BES Developer’s Guide