Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.nutch.protocol.httpclient; // JDK imports import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.net.URL; import org.apache.commons.httpclient.Header; import org.apache.commons.httpclient.HttpException; import org.apache.commons.httpclient.HttpVersion; import org.apache.commons.httpclient.cookie.CookiePolicy; import org.apache.commons.httpclient.methods.GetMethod; import org.apache.commons.httpclient.params.HttpMethodParams; import org.apache.nutch.crawl.CrawlDatum; import org.apache.nutch.metadata.Metadata; import org.apache.nutch.metadata.SpellCheckedMetadata; import org.apache.nutch.net.protocols.HttpDateFormat; import org.apache.nutch.net.protocols.Response; import org.apache.nutch.protocol.http.api.HttpBase; /** * An HTTP response. * * @author Susam Pal */ public class HttpResponseBak implements Response { private URL url; private byte[] content; private int code; private Metadata headers = new SpellCheckedMetadata(); /** * Fetches the given <code>url</code> and prepares HTTP response. * * @param http An instance of the implementation class * of this plugin * @param url URL to be fetched * @param datum Crawl data * @param followRedirects Whether to follow redirects; follows * redirect if and only if this is true * @return HTTP response * @throws IOException When an error occurs */ HttpResponseBak(HttpBak http, URL url, CrawlDatum datum, boolean followRedirects) throws IOException { // Prepare GET method for HTTP request this.url = url; GetMethod get = new GetMethod(url.toString()); get.setFollowRedirects(followRedirects); get.setDoAuthentication(true); if (datum.getModifiedTime() > 0) { get.setRequestHeader("If-Modified-Since", HttpDateFormat.toString(datum.getModifiedTime())); } // Set HTTP parameters HttpMethodParams params = get.getParams(); if (http.getUseHttp11()) { params.setVersion(HttpVersion.HTTP_1_1); } else { params.setVersion(HttpVersion.HTTP_1_0); } params.makeLenient(); params.setContentCharset("UTF-8"); params.setCookiePolicy(CookiePolicy.BROWSER_COMPATIBILITY); params.setBooleanParameter(HttpMethodParams.SINGLE_COOKIE_HEADER, true); // XXX (ab) not sure about this... the default is to retry 3 times; if // XXX the request body was sent the method is not retried, so there is // XXX little danger in retrying... // params.setParameter(HttpMethodParams.RETRY_HANDLER, null); try { code = Http.getClient().executeMethod(get); Header[] heads = get.getResponseHeaders(); for (int i = 0; i < heads.length; i++) { headers.set(heads[i].getName(), heads[i].getValue()); } // Limit download size int contentLength = Integer.MAX_VALUE; String contentLengthString = headers.get(Response.CONTENT_LENGTH); if (contentLengthString != null) { try { contentLength = Integer.parseInt(contentLengthString.trim()); } catch (NumberFormatException ex) { throw new HttpException("bad content length: " + contentLengthString); } } if (http.getMaxContent() >= 0 && contentLength > http.getMaxContent()) { contentLength = http.getMaxContent(); } // always read content. Sometimes content is useful to find a cause // for error. InputStream in = get.getResponseBodyAsStream(); try { byte[] buffer = new byte[HttpBase.BUFFER_SIZE]; int bufferFilled = 0; int totalRead = 0; ByteArrayOutputStream out = new ByteArrayOutputStream(); while ((bufferFilled = in.read(buffer, 0, buffer.length)) != -1 && totalRead + bufferFilled <= contentLength) { totalRead += bufferFilled; out.write(buffer, 0, bufferFilled); } content = out.toByteArray(); } catch (Exception e) { if (code == 200) throw new IOException(e.toString()); // for codes other than 200 OK, we are fine with empty content } finally { if (in != null) { in.close(); } get.abort(); } StringBuilder fetchTrace = null; if (Http.LOG.isTraceEnabled()) { // Trace message fetchTrace = new StringBuilder( "url: " + url + "; status code: " + code + "; bytes received: " + content.length); if (getHeader(Response.CONTENT_LENGTH) != null) fetchTrace.append("; Content-Length: " + getHeader(Response.CONTENT_LENGTH)); if (getHeader(Response.LOCATION) != null) fetchTrace.append("; Location: " + getHeader(Response.LOCATION)); } // Extract gzip, x-gzip and deflate content if (content != null) { // check if we have to uncompress it String contentEncoding = headers.get(Response.CONTENT_ENCODING); if (contentEncoding != null && Http.LOG.isTraceEnabled()) fetchTrace.append("; Content-Encoding: " + contentEncoding); if ("gzip".equals(contentEncoding) || "x-gzip".equals(contentEncoding)) { content = http.processGzipEncoded(content, url); if (Http.LOG.isTraceEnabled()) fetchTrace.append("; extracted to " + content.length + " bytes"); } else if ("deflate".equals(contentEncoding)) { content = http.processDeflateEncoded(content, url); if (Http.LOG.isTraceEnabled()) fetchTrace.append("; extracted to " + content.length + " bytes"); } } // Logger trace message if (Http.LOG.isTraceEnabled()) { Http.LOG.trace(fetchTrace.toString()); } } finally { get.releaseConnection(); } } /* ------------------------- * * <implementation:Response> * * ------------------------- */ public URL getUrl() { return url; } public int getCode() { return code; } public String getHeader(String name) { return headers.get(name); } public Metadata getHeaders() { return headers; } public byte[] getContent() { return content; } /* -------------------------- * * </implementation:Response> * * -------------------------- */ }