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.net.urlnormalizer.slash; import java.lang.invoke.MethodHandles; import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.io.Reader; import java.io.StringReader; import java.net.MalformedURLException; import java.net.URL; import java.util.HashMap; import java.util.Map; import org.apache.commons.lang.StringUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.apache.hadoop.conf.Configuration; import org.apache.nutch.crawl.CrawlDatum; import org.apache.nutch.net.URLNormalizer; import org.apache.nutch.plugin.Extension; import org.apache.nutch.plugin.PluginRepository; /** * @author markus@openindex.io */ public class SlashURLNormalizer implements URLNormalizer { private Configuration conf; private static final Logger LOG = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass()); private static final char QUESTION_MARK = '?'; private static final char SLASH = '/'; private static final char DOT = '.'; private static final String PROTOCOL_DELIMITER = "://"; private static String attributeFile = null; private String slashesFile = null; // We record a map of hosts and boolean, the boolean denotes whether the host should // have slashes after URL paths. True means slash, false means remove the slash private static final Map<String, Boolean> slashesMap = new HashMap<>(); public SlashURLNormalizer() { //default constructor } public SlashURLNormalizer(String slashesFile) { this.slashesFile = slashesFile; } private synchronized void readConfiguration(Reader configReader) throws IOException { if (slashesMap.size() > 0) { return; } BufferedReader reader = new BufferedReader(configReader); String line, host; String rule; int delimiterIndex; while ((line = reader.readLine()) != null) { if (StringUtils.isNotBlank(line) && !line.startsWith("#")) { line = line.trim(); delimiterIndex = line.indexOf(" "); // try tabulator if (delimiterIndex == -1) { delimiterIndex = line.indexOf("\t"); } host = line.substring(0, delimiterIndex); rule = line.substring(delimiterIndex + 1).trim(); if (rule.equals("+")) { slashesMap.put(host, true); } else { slashesMap.put(host, false); } } } } public Configuration getConf() { return conf; } public void setConf(Configuration conf) { this.conf = conf; // get the extensions for domain urlfilter String pluginName = "urlnormalizer-slash"; Extension[] extensions = PluginRepository.get(conf).getExtensionPoint(URLNormalizer.class.getName()) .getExtensions(); for (int i = 0; i < extensions.length; i++) { Extension extension = extensions[i]; if (extension.getDescriptor().getPluginId().equals(pluginName)) { attributeFile = extension.getAttribute("file"); break; } } // handle blank non empty input if (attributeFile != null && attributeFile.trim().equals("")) { attributeFile = null; } if (attributeFile != null) { if (LOG.isInfoEnabled()) { LOG.info("Attribute \"file\" is defined for plugin " + pluginName + " as " + attributeFile); } } else { if (LOG.isWarnEnabled()) { LOG.warn("Attribute \"file\" is not defined in plugin.xml for plugin " + pluginName); } } // domain file and attribute "file" take precedence if defined String file = conf.get("urlnormalizer.slashes.file"); String stringRules = conf.get("urlnormalizer.slashes.rules"); if (slashesFile != null) { file = slashesFile; } else if (attributeFile != null) { file = attributeFile; } Reader reader = null; if (stringRules != null) { // takes precedence over files reader = new StringReader(stringRules); } else { reader = conf.getConfResourceAsReader(file); } try { if (reader == null) { reader = new FileReader(file); } readConfiguration(reader); } catch (IOException e) { LOG.error(org.apache.hadoop.util.StringUtils.stringifyException(e)); } } public String normalize(String url, String scope) throws MalformedURLException { return normalize(url, null, scope); } public String normalize(String url, CrawlDatum crawlDatum, String scope) throws MalformedURLException { // Get URL repr. URL u = new URL(url); // Get the host String host = u.getHost(); // Do we have a rule for this host? if (slashesMap.containsKey(host)) { // Yes, separate the path and optional querystring String protocol = u.getProtocol(); String path = u.getPath(); // Don't do anything to root URL's // / is always set by basic normalizer if (path.length() > 1) { String queryString = u.getQuery(); // Get the rule boolean rule = slashesMap.get(host); // Does it have a trailing slash int lastIndexOfSlash = path.lastIndexOf(SLASH); boolean trailingSlash = (lastIndexOfSlash == path.length() - 1); // Do we need to add a trailing slash? if (!trailingSlash && rule) { // Only add a trailing slash if this path doesn't appear to have an extension/suffix such as .html int lastIndexOfDot = path.lastIndexOf(DOT); if (path.length() < 6 || lastIndexOfDot == -1 || lastIndexOfDot < path.length() - 6) { StringBuilder buffer = new StringBuilder(protocol); buffer.append(PROTOCOL_DELIMITER); buffer.append(host); buffer.append(path); buffer.append(SLASH); if (queryString != null) { buffer.append(QUESTION_MARK); buffer.append(queryString); } url = buffer.toString(); } } // Do we need to remove a trailing slash? else if (trailingSlash && !rule) { StringBuilder buffer = new StringBuilder(protocol); buffer.append(PROTOCOL_DELIMITER); buffer.append(host); buffer.append(path.substring(0, lastIndexOfSlash)); if (queryString != null) { buffer.append(QUESTION_MARK); buffer.append(queryString); } url = buffer.toString(); } } } return url; } }