URI::Fetch(3pm) - phpMan

URI::Fetch(3pm) User Contributed Perl Documentation URI::Fetch(3pm)

NAME
URI::Fetch - Smart URI fetching/caching

SYNOPSIS
use URI::Fetch;

## Simple fetch.
my $res = URI::Fetch->fetch('http://example.com/atom.xml')
or die URI::Fetch->errstr;

## Fetch using specified ETag and Last-Modified headers.
my $res = URI::Fetch->fetch('http://example.com/atom.xml',
ETag => '123-ABC',
LastModified => time - 3600,
)
or die URI::Fetch->errstr;

## Fetch using an on-disk cache that URI::Fetch manages for you.
my $cache = Cache::File->new( cache_root => '/tmp/cache' );
my $res = URI::Fetch->fetch('http://example.com/atom.xml',
Cache => $cache
)
or die URI::Fetch->errstr;

DESCRIPTION
URI::Fetch is a smart client for fetching HTTP pages, notably syndication feeds (RSS,
Atom, and others), in an intelligent, bandwidth- and time-saving way. That means:

* GZIP support
If you have Compress::Zlib installed, URI::Fetch will automatically try to download a
compressed version of the content, saving bandwidth (and time).

* Last-Modified and ETag support
If you use a local cache (see the Cache parameter to fetch), URI::Fetch will keep
track of the Last-Modified and ETag headers from the server, allowing you to only
download pages that have been modified since the last time you checked.

* Proper understanding of HTTP error codes
Certain HTTP error codes are special, particularly when fetching syndication feeds,
and well-written clients should pay special attention to them. URI::Fetch can only do
so much for you in this regard, but it gives you the tools to be a well-written
client.

The response from fetch gives you the raw HTTP response code, along with special han-
dling of 4 codes:

* 200 (OK)
Signals that the content of a page/feed was retrieved successfully.

* 301 (Moved Permanently)
Signals that a page/feed has moved permanently, and that your database of feeds
should be updated to reflect the new URI.

* 304 (Not Modified)
Signals that a page/feed has not changed since it was last fetched.

* 410 (Gone)
Signals that a page/feed is gone and will never be coming back, so you should stop
trying to fetch it.

USAGE
URI::Fetch->fetch($uri, %param)

Fetches a page identified by the URI $uri.

On success, returns a URI::Fetch::Response object; on failure, returns "undef".

%param can contain:

* LastModified
* ETag
LastModified and ETag can be supplied to force the server to only return the full page
if it's changed since the last request. If you're writing your own feed client, this
is recommended practice, because it limits both your bandwidth use and the server's.

If you'd rather not have to store the LastModified time and ETag yourself, see the
Cache parameter below (and the SYNOPSIS above).

* Cache
If you'd like URI::Fetch to cache responses between requests, provide the Cache param-
eter with an object supporting the Cache API (e.g. Cache::File, Cache::Memory).
Specifically, an object that supports "$cache->get($key)" and "$cache->set($key,
$value, $expires)".

If supplied, URI::Fetch will store the page content, ETag, and last-modified time of
the response in the cache, and will pull the content from the cache on subsequent
requests if the page returns a Not-Modified response.

* UserAgent
Optional. You may provide your own LWP::UserAgent instance. Look into LWPx::Para-
noidUserAgent if you're fetching URLs given to you by possibly malicious parties.

* NoNetwork
Optional. Controls the interaction between the cache and HTTP requests with If-Modi-
fied-Since/If-None-Match headers. Possible behaviors are:

false (default)
If a page is in the cache, the origin HTTP server is always checked for a fresher
copy with an If-Modified-Since and/or If-None-Match header.

1 If set to 1, the origin HTTP is never contacted, regardless of the page being in
cache or not. If the page is missing from cache, the fetch method will return
undef. If the page is in cache, that page will be returned, no matter how old it
is. Note that setting this option means the URI::Fetch::Response object will
never have the http_response member set.

"N", where N > 1
The origin HTTP server is not contacted if the page is in cache and the cached
page was inserted in the last N seconds. If the cached copy is older than N sec-
onds, a normal HTTP request (full or cache check) is done.

* ContentAlterHook
Optional. A subref that gets called with a scalar reference to your content so you
can modify the content before it's returned and before it's put in cache.

For instance, you may want to only cache the <head> section of an HTML document, or
you may want to take a feed URL and cache only a pre-parsed version of it. If you
modify the scalarref given to your hook and change it into a hashref, scalarref, or
some blessed object, that same value will be returned to you later on not-modified
responses.

* CacheEntryGrep
Optional. A subref that gets called with the URI::Fetch::Response object about to be
cached (with the contents already possibly transformed by your "ContentAlterHook").
If your subref returns true, the page goes into the cache. If false, it doesn't.

* Freeze
* Thaw
Optional. Subrefs that get called to serialize and deserialize, respectively, the data
that will be cached. The cached data should be assumed to be an arbitrary Perl data
structure, containing (potentially) references to arrays, hashes, etc.

Freeze should serialize the structure into a scalar; Thaw should deserialize the
scalar into a data structure.

By default, Storable will be used for freezing and thawing the cached data structure.

* ForceResponse
Optional. A boolean that indicates a URI::Fetch::Response should be returned regard-
less of the HTTP status. By default "undef" is returned when a response is not a "suc-
cess" (200 codes) or one of the recognized HTTP status codes listed above. The HTTP
status message can then be retreived using the "errstr" method on the class.

LICENSE
URI::Fetch is free software; you may redistribute it and/or modify it under the same terms
as Perl itself.

perl v5.8.8 2006-08-23 URI::Fetch(3pm)

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