speed feeds refresh up by using http headers

src/main/java/com/commafeed/backend/HttpGetter.java

@@ -2,9 +2,14 @@ package com.commafeed.backend;
 
 import java.io.IOException;
 
+import org.apache.commons.lang.StringUtils;
+import org.apache.http.Header;
 import org.apache.http.HttpEntity;
+import org.apache.http.HttpHeaders;
 import org.apache.http.HttpResponse;
+import org.apache.http.HttpStatus;
 import org.apache.http.client.ClientProtocolException;
+import org.apache.http.client.HttpResponseException;
 import org.apache.http.client.methods.HttpGet;
 import org.apache.http.client.params.CookiePolicy;
 import org.apache.http.client.params.HttpClientParams;
@@ -16,13 +21,28 @@ import org.apache.http.util.EntityUtils;
 
 public class HttpGetter {
 
-	public String get(String url) throws Exception {
-		return new String(getBinary(url), "UTF-8");
+	public HttpResult getBinary(String url) throws ClientProtocolException,
+			IOException, NotModifiedException {
+		return getBinary(url, null, null);
 	}
 
-	public byte[] getBinary(String url) throws ClientProtocolException,
-			IOException {
-		byte[] content = null;
+	/**
+	 * 
+	 * @param url
+	 *            the url to retrive
+	 * @param lastModified
+	 *            header we got last time we queried that url, or null
+	 * @param eTag
+	 *            header we got last time we queried that url, or null
+	 * @return
+	 * @throws ClientProtocolException
+	 * @throws IOException
+	 * @throws NotModifiedException
+	 *             if the url hasn't changed since we asked for it last time
+	 */
+	public HttpResult getBinary(String url, String lastModified, String eTag)
+			throws ClientProtocolException, IOException, NotModifiedException {
+		HttpResult result = null;
 
 		DefaultHttpClient httpclient = new DefaultHttpClient();
 		HttpParams params = httpclient.getParams();
@@ -35,14 +55,85 @@ public class HttpGetter {
 			HttpGet httpget = new HttpGet(url);
 			httpget.addHeader("Pragma", "No-cache");
 			httpget.addHeader("Cache-Control", "no-cache");
-			HttpResponse response = httpclient.execute(httpget);
+
+			if (lastModified != null) {
+				httpget.addHeader(HttpHeaders.IF_MODIFIED_SINCE, lastModified);
+			}
+			if (eTag != null) {
+				httpget.addHeader(HttpHeaders.IF_NONE_MATCH, eTag);
+			}
+
+			HttpResponse response = null;
+			try {
+				response = httpclient.execute(httpget);
+				if (response.getStatusLine().getStatusCode() == HttpStatus.SC_NOT_MODIFIED) {
+					throw new NotModifiedException();
+				}
+			} catch (HttpResponseException e) {
+				if (e.getStatusCode() == HttpStatus.SC_NOT_MODIFIED) {
+					throw new NotModifiedException();
+				}
+			}
+			Header lastModifiedHeader = response
+					.getFirstHeader(HttpHeaders.LAST_MODIFIED);
+			Header eTagHeader = response.getFirstHeader(HttpHeaders.ETAG);
 			HttpEntity entity = response.getEntity();
+
+			String lastModifiedResponse = lastModifiedHeader == null ? null
+					: lastModifiedHeader.getValue();
+			String eTagResponse = eTagHeader == null ? null : eTagHeader
+					.getValue();
+
+			if (lastModified != null
+					&& StringUtils.equals(lastModified, lastModifiedResponse)) {
+				throw new NotModifiedException();
+			}
+
+			if (eTag != null && StringUtils.equals(eTag, eTagResponse)) {
+				throw new NotModifiedException();
+			}
+
+			byte[] content = null;
 			if (entity != null) {
 				content = EntityUtils.toByteArray(entity);
 			}
+			result = new HttpResult(content, lastModifiedHeader == null ? null
+					: lastModifiedHeader.getValue(), eTagHeader == null ? null
+					: eTagHeader.getValue());
 		} finally {
 			httpclient.getConnectionManager().shutdown();
 		}
-		return content;
+		return result;
+	}
+
+	public static class HttpResult {
+
+		private byte[] content;
+		private String lastModifiedSince;
+		private String eTag;
+
+		public HttpResult(byte[] content, String lastModifiedSince, String eTag) {
+			this.content = content;
+			this.lastModifiedSince = lastModifiedSince;
+			this.eTag = eTag;
+		}
+
+		public byte[] getContent() {
+			return content;
+		}
+
+		public String getLastModifiedSince() {
+			return lastModifiedSince;
+		}
+
+		public String geteTag() {
+			return eTag;
+		}
+
+	}
+
+	public static class NotModifiedException extends Exception {
+		private static final long serialVersionUID = 1L;
+
 	}
 }