Java tutorial
/* * RSSFetcher.java * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Library General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * Author: Winter Lau (javayou@gmail.com) * http://dlog4j.sourceforge.net */ package com.liusoft.dlog4j.xml; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.URL; import java.nio.charset.Charset; import java.text.MessageFormat; import java.text.ParseException; import java.util.Iterator; import java.util.Properties; import javax.servlet.http.HttpServletResponse; import net.sf.ehcache.Cache; import net.sf.ehcache.CacheException; import net.sf.ehcache.Element; import org.apache.commons.digester.Digester; import org.apache.commons.digester.rss.Channel; import org.apache.commons.httpclient.Header; import org.apache.commons.httpclient.HttpClient; import org.apache.commons.httpclient.HttpException; import org.apache.commons.httpclient.methods.GetMethod; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.xml.sax.SAXException; import com.liusoft.dlog4j.DLOG_CacheManager; /** * RSS?? * @author Winter Lau */ public class RSSFetcher { final static HttpClient http_client = new HttpClient(); final static Log log = LogFactory.getLog(RSSFetcher.class); final static Cache channels = DLOG_CacheManager.getRssCache(); private final static Properties charsets = new Properties(); static { InputStream in = RSSFetcher.class.getResourceAsStream("rss.properties"); try { charsets.load(in); } catch (IOException e) { log.error("Exception occur when loading rss.properties", e); } } /** * ?? * ???? * @param type * @param url * @return */ public static Channel fetchChannel(int type, String url) { //get from the cache if (channels != null) { try { Element channel = channels.get(url); if (channel != null) return (Channel) channel.getValue(); } catch (IllegalStateException e) { //occur when this element is expire } catch (CacheException e) { log.error("Exception occurred when get from cache " + url, e); } } //fetch from http directly try { Channel channel = fetchChannelViaHTTP(url); if (channels != null && channel != null) { channels.put(new Element(url, channel)); } return channel; } catch (Exception e) { log.error("Exception occurred when fetch " + url, e); } return null; } private static Header getResponseHeader(GetMethod m, String name) { Header[] headers = m.getResponseHeaders(); for (int i = 0; i < headers.length; i++) { if (headers[i].getName().equalsIgnoreCase(name)) return headers[i]; } return null; } /** * ?? * @param type * @param url * @return * @throws IOException * @throws HttpException * @throws SAXException * @throws ParseException */ private static Channel fetchChannelViaHTTP(String url) throws HttpException, IOException, SAXException { Digester parser = new XMLDigester(); GetMethod get = new GetMethod(url); //get.setRequestHeader("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; zh-cn) Opera 8.52"); try { http_client.executeMethod(get); if (get.getStatusCode() == HttpServletResponse.SC_OK) { Charset cs = null; Header header_cs = getResponseHeader(get, "Content-Type"); if (header_cs == null) { cs = Charset.forName(get.getResponseCharSet()); } else { String content_type = header_cs.getValue().toLowerCase(); try { Object[] values = content_type_parser.parse(content_type); cs = Charset.forName((String) values[1]); } catch (ParseException e) { URL o_url = new URL(url); String host = o_url.getHost(); Iterator hosts = charsets.keySet().iterator(); while (hosts.hasNext()) { String t_host = (String) hosts.next(); if (host.toLowerCase().endsWith(t_host)) { cs = Charset.forName((String) charsets.get(t_host)); break; } } if (cs == null) cs = default_charset; } } BufferedReader rd = new BufferedReader(new InputStreamReader(get.getResponseBodyAsStream(), cs)); char[] cbuf = new char[1]; int read_idx = 1; do { rd.mark(read_idx++); if (rd.read(cbuf) == -1) break; if (cbuf[0] != '<') continue; rd.reset(); break; } while (true); return (Channel) parser.parse(rd); } else { log.error("Fetch RSS from " + url + " failed, code=" + get.getStatusCode()); } } finally { get.releaseConnection(); } return null; } private final static Charset default_charset = Charset.forName("utf-8"); private final static MessageFormat content_type_parser = new MessageFormat("{0};charset={1}"); /** * @param args * @throws Exception */ public static void main(String[] args) throws Exception { Channel ch1 = fetchChannelViaHTTP("http://unruledboy.cnblogs.com/Rss.aspx"); System.out.println(ch1.getTitle()); for (int i = 0; i < ch1.getItems().length; i++) { ChannelItem item = (ChannelItem) ch1.getItems()[i]; System.out.println(item.getDescription()); } } }