Apache::OutputChain was written to
explore
the
possibilities of stacked handlers in
mod_perl. It ties STDOUT to an object that catches
the output and makes it easy to build a chain of modules that work on
the output data stream.
Examples of modules that are built using this idea are
Apache::SSIChain,
Apache::GzipChain, and
Apache::EmbperlChain—the first processes the
SSIs in the stream, the second compresses the output on the fly, and
the last provides Embperl processing.
The modules are listed in reverse order of their
execution—here the Apache::PassHtml module
simply collects a file's content and sends it to
STDOUT, and then it's processed
by Apache::SSIChain, which sends its output to
STDOUT again. Then it's processed
by Apache::OutputChain, which finally sends the
result to the browser.
An alternative to this approach is Apache::Filter,
which has a more natural forward configuration
order and is easier to interface with other modules.
Apache::OutputChain works with
Apache::Registry as well. For example:
It's really a regular
Apache::Registrysetup, except for the added
modules in the PerlHandler line.
Available from CPAN. See the module manpage for more information.
B.15.2. Apache::Clean—mod_perl Interface Into HTML::Clean
Apache::Clean uses HTML::Clean
to tidy up
large, messy HTML, saving bandwidth. It
is particularly useful with Apache::Compress for
maximum size reduction.
Available from CPAN. See the module manpage for more information.
B.15.3. Apache::Filter—Alter the Output of Previous Handlers
each of the handlers Filter1,
Filter2, and
Filter3 will make a call to
$r->filter_input( ), which will return a file
handle. For Filter1, the file handle points to the
requested file. For Filter2, the file handle
contains whatever Filter1 wrote to
STDOUT. For Filter3, it
contains whatever Filter2 wrote to
STDOUT. The output of Filter3
goes directly to the browser.
Available from CPAN. See the module manpage for more information.
B.15.4. Apache::GzipChain—Compress HTML (or Anything) in the OutputChain
You can test that it works by either looking at the size of the
response in the access.log file or by telnet:
panic% telnet localhost 8000
Trying 127.0.0.1
Connected to 127.0.0.1
Escape character is '^]'.
GET /perl/test.pl HTTP 1.1
Accept-Encoding: gzip
User-Agent: Mozilla
You will get the data compressed if it's configured
correctly.
B.15.7. Apache::Compress—Auto-Compress Web Files with gzip
This module lets you send the
content of an HTTP response as
gzip-compressed data. Certain browsers (e.g.,
Netscape and IE) can request content compression via the
Content-Encoding header. This can speed things up
if you're sending large files to your users through
slow connections.
Browsers that don't request
gzipped data will receive uncompressed data.
This module is compatibile with Apache::Filter, so
you can compress the output of other content generators.
Available from CPAN. See the module manpage for more information.
B.15.8. Apache::Layer—Layer Content Tree Over One or More Others
This module is designed to allow
multiple content trees to be layered on
top of each other within the Apache server.
Available from CPAN. See the module manpage for more information.
The Apache::Sandwich module allows
you to add per-directory custom
"header" and
"footer" content to a given URI.
Works only with GET requests. Output of combined
parts is forced to text/html. The handler for
the sandwiched document is specified by the
SandwichHandler configuration variable. If it is
not set, default-handler is used.
The basic concept is that the concatenation of the header and footer
parts with the sandwiched file in between constitutes a complete
valid HTML document.
Available from CPAN. See the module manpage for more information.
Apache::SimpleReplace provides a simple
way to insert content within an
established template for uniform content delivery. While the end
result is similar to Apache::Sandwich,
Apache::SimpleReplace offers two main advantages:
It does not use separate header and footer files, easing the pain of
maintaining syntactically correct HTML in separate files.
It is Apache::Filter aware, so it can both accept
content from other content handlers and pass its changes on to others
later in the chain.
Available from CPAN. See the module manpage for more information.
B.15.11. Apache::SSI—Implement Server-Side Includes in Perl
Apache::SSI implements the functionality
of mod_include for handling server-parsed
HTML documents. It runs under Apache's mod_perl.
There are two main reasons you might want to use this module: you can
subclass it to implement your own custom SSI directives, and you can
parse the output of other mod_perl handlers or send the SSI output
through another handler (use Apache::Filter to do
this).
Available from CPAN. See the module manpage for more information.
B.14. Toolkits and Frameworks for Content-Generation and Other Phases
