org.rometools.fetcher.impl
Class HttpURLFeedFetcher

java.lang.Object
  org.rometools.fetcher.impl.AbstractFeedFetcher
      org.rometools.fetcher.impl.HttpURLFeedFetcher

All Implemented Interfaces:

FeedFetcher

public class HttpURLFeedFetcher
extends AbstractFeedFetcher

Class to retrieve syndication files via HTTP.

If passed a FeedFetcherCache in the constructor it will use conditional gets to only retrieve modified content.

The class uses the Accept-Encoding: gzip header to retrieve gzipped feeds where supported by the server.

Simple usage:

        // create the cache
        FeedFetcherCache feedInfoCache = HashMapFeedInfoCache.getFeedInfoCache();
        // retrieve the feed the first time
        // any subsequent request will use conditional gets and only
        // retrieve the resource if it has changed
        SyndFeed feed = new HttpURLFeedFetcher(feedInfoCache).retrieveFeed(feedUrl);

Author:

Nick Lothian

See Also:

http://fishbowl.pastiche.org/2002/10/21/http_conditional_get_for_rss_hackers, http://diveintomark.org/archives/2003/07/21/atom_aggregator_behavior_http_level, http://bobwyman.pubsub.com/main/2004/09/using_rfc3229_w.html

Field Summary

Fields inherited from interface org.rometools.fetcher.FeedFetcher

DEFAULT_USER_AGENT

Constructor Summary

HttpURLFeedFetcher()
Constructor to use HttpURLFeedFetcher without caching of feeds

HttpURLFeedFetcher(FeedFetcherCache feedInfoCache)
Constructor to enable HttpURLFeedFetcher to cache feeds

Method Summary

FeedFetcherCache	getFeedInfoCache()
protected void	resetFeedInfo(URL orignalUrl, SyndFeedInfo syndFeedInfo, HttpURLConnection connection)
protected void	retrieveAndCacheFeed(URL feedUrl, SyndFeedInfo syndFeedInfo, HttpURLConnection connection)
com.sun.syndication.feed.synd.SyndFeed	retrieveFeed(String userAgent, URL feedUrl) Retrieve a feed over HTTP
com.sun.syndication.feed.synd.SyndFeed	retrieveFeed(URL feedUrl) Retrieve a feed over HTTP
void	setFeedInfoCache(FeedFetcherCache cache)
protected void	setRequestHeaders(URLConnection connection, SyndFeedInfo syndFeedInfo) Set appropriate HTTP headers, including conditional get and gzip encoding headers

Methods inherited from class org.rometools.fetcher.impl.AbstractFeedFetcher

addFetcherEventListener, combineFeeds, fireEvent, fireEvent, fireEvent, fireEvent, getUserAgent, handleErrorCodes, isPreserveWireFeed, isUsingDeltaEncoding, removeFetcherEventListener, setPreserveWireFeed, setUserAgent, setUsingDeltaEncoding, throw4XXError, throwAuthenticationError

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

HttpURLFeedFetcher

public HttpURLFeedFetcher()

Constructor to use HttpURLFeedFetcher without caching of feeds

HttpURLFeedFetcher

public HttpURLFeedFetcher(FeedFetcherCache feedInfoCache)

Constructor to enable HttpURLFeedFetcher to cache feeds

Parameters:

feedCache - - an instance of the FeedFetcherCache interface

Method Detail

retrieveFeed

public com.sun.syndication.feed.synd.SyndFeed retrieveFeed(URL feedUrl)
                                                    throws IllegalArgumentException,
                                                           IOException,
                                                           com.sun.syndication.io.FeedException,
                                                           FetcherException

Description copied from interface: FeedFetcher

Retrieve a feed over HTTP

Parameters:

feedUrl - A non-null URL of a RSS/Atom feed to retrieve

Returns:

A SyndFeed object

Throws:

IllegalArgumentException - if the URL is null;

IOException - if a TCP error occurs

com.sun.syndication.io.FeedException - if the feed is not valid

FetcherException - if a HTTP error occurred

retrieveFeed

public com.sun.syndication.feed.synd.SyndFeed retrieveFeed(String userAgent,
                                                           URL feedUrl)
                                                    throws IllegalArgumentException,
                                                           IOException,
                                                           com.sun.syndication.io.FeedException,
                                                           FetcherException

Retrieve a feed over HTTP

Parameters:

feedUrl - A non-null URL of a RSS/Atom feed to retrieve

Returns:

A SyndFeed object

Throws:

IllegalArgumentException - if the URL is null;

IOException - if a TCP error occurs

com.sun.syndication.io.FeedException - if the feed is not valid

FetcherException - if a HTTP error occurred

retrieveAndCacheFeed

protected void retrieveAndCacheFeed(URL feedUrl,
                                    SyndFeedInfo syndFeedInfo,
                                    HttpURLConnection connection)
                             throws IllegalArgumentException,
                                    com.sun.syndication.io.FeedException,
                                    FetcherException,
                                    IOException

Throws:

IllegalArgumentException

com.sun.syndication.io.FeedException

FetcherException

IOException

resetFeedInfo

protected void resetFeedInfo(URL orignalUrl,
                             SyndFeedInfo syndFeedInfo,
                             HttpURLConnection connection)
                      throws IllegalArgumentException,
                             IOException,
                             com.sun.syndication.io.FeedException

Throws:

IllegalArgumentException

IOException

com.sun.syndication.io.FeedException

setRequestHeaders

protected void setRequestHeaders(URLConnection connection,
                                 SyndFeedInfo syndFeedInfo)

Set appropriate HTTP headers, including conditional get and gzip encoding headers

Parameters:

connection - A URLConnection

syndFeedInfo - The SyndFeedInfo for the feed to be retrieved. May be null

getFeedInfoCache

public FeedFetcherCache getFeedInfoCache()

Returns:

The FeedFetcherCache used by this fetcher (Could be null)

setFeedInfoCache

public void setFeedInfoCache(FeedFetcherCache cache)

Parameters:

cache - The cache to be used by this fetcher (pass null to stop using a cache)