add gzip support

webmagic-core/src/main/java/us/codecraft/webmagic/downloader/HttpClientDownloader.java

 package us.codecraft.webmagic.downloader;
 
 import org.apache.commons.io.IOUtils;
+import org.apache.http.Header;
+import org.apache.http.HeaderElement;
 import org.apache.http.HttpResponse;
 import org.apache.http.client.HttpClient;
+import org.apache.http.client.entity.GzipDecompressingEntity;
 import org.apache.http.client.methods.HttpGet;
 import org.apache.log4j.Logger;
 import us.codecraft.webmagic.Page;
@@ -26,15 +29,19 @@ public class HttpClientDownloader implements Downloader {
     public Page download(Request request, Site site) {
         logger.info("downloading page " + request.getUrl());
         HttpClient httpClient = HttpClientPool.getInstance().getClient(site);
+        String encoding = site.getEncoding();
         try {
             HttpGet httpGet = new HttpGet(request.getUrl());
             HttpResponse httpResponse = httpClient.execute(httpGet);
             int statusCode = httpResponse.getStatusLine().getStatusCode();
             if (site.getAcceptStatCode().contains(statusCode)) {
-                if (site.getEncoding() == null){
+                //charset
+                if (encoding == null){
                     String value = httpResponse.getEntity().getContentType().getValue();
                     site.setEncoding(new PlainText(value).regex("charset=([^\\s]+)").toString());
                 }
+                //
+                handleGzip(httpResponse);
                 String content = IOUtils.toString(httpResponse.getEntity().getContent(),
                          site.getEncoding());
                 Page page = new Page();
@@ -50,4 +57,17 @@ public class HttpClientDownloader implements Downloader {
         }
         return null;
     }
+
+    private void handleGzip(HttpResponse httpResponse) {
+        Header ceheader = httpResponse.getEntity().getContentEncoding();
+        if (ceheader != null) {
+            HeaderElement[] codecs = ceheader.getElements();
+            for (int i = 0; i < codecs.length; i++) {
+                if (codecs[i].getName().equalsIgnoreCase("gzip")) {
+                    httpResponse.setEntity(
+                            new GzipDecompressingEntity(httpResponse.getEntity()));
+                }
+            }
+        }
+    }
 }