forked from Archives/Athou_commafeed
extracted needed classes and remove crawler4j dependency and java7 requirement
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Athou
211
src/main/java/edu/uci/ics/crawler4j/url/URLCanonicalizer.java
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211
src/main/java/edu/uci/ics/crawler4j/url/URLCanonicalizer.java
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/**
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package edu.uci.ics.crawler4j.url;
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import java.net.MalformedURLException;
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import java.net.URI;
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import java.net.URISyntaxException;
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import java.net.URL;
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import java.net.URLDecoder;
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import java.net.URLEncoder;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.SortedMap;
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import java.util.TreeMap;
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/**
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* See http://en.wikipedia.org/wiki/URL_normalization for a reference Note: some
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* parts of the code are adapted from: http://stackoverflow.com/a/4057470/405418
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*
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* @author Yasser Ganjisaffar <lastname at gmail dot com>
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*/
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public class URLCanonicalizer {
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public static String getCanonicalURL(String url) {
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return getCanonicalURL(url, null);
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}
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public static String getCanonicalURL(String href, String context) {
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try {
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URL canonicalURL = new URL(UrlResolver.resolveUrl(context == null ? "" : context, href));
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String host = canonicalURL.getHost().toLowerCase();
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if (host == "") {
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// This is an invalid Url.
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return null;
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}
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String path = canonicalURL.getPath();
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/*
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* Normalize: no empty segments (i.e., "//"), no segments equal to
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* ".", and no segments equal to ".." that are preceded by a segment
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* not equal to "..".
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*/
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path = new URI(path).normalize().toString();
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/*
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* Convert '//' -> '/'
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*/
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int idx = path.indexOf("//");
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while (idx >= 0) {
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path = path.replace("//", "/");
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idx = path.indexOf("//");
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}
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/*
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* Drop starting '/../'
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*/
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while (path.startsWith("/../")) {
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path = path.substring(3);
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}
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/*
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* Trim
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*/
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path = path.trim();
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final SortedMap<String, String> params = createParameterMap(canonicalURL.getQuery());
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final String queryString;
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if (params != null && params.size() > 0) {
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String canonicalParams = canonicalize(params);
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queryString = (canonicalParams.isEmpty() ? "" : "?" + canonicalParams);
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} else {
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queryString = "";
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}
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/*
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* Add starting slash if needed
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*/
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if (path.length() == 0) {
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path = "/" + path;
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}
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/*
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* Drop default port: example.com:80 -> example.com
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*/
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int port = canonicalURL.getPort();
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if (port == canonicalURL.getDefaultPort()) {
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port = -1;
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}
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String protocol = canonicalURL.getProtocol().toLowerCase();
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String pathAndQueryString = normalizePath(path) + queryString;
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URL result = new URL(protocol, host, port, pathAndQueryString);
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return result.toExternalForm();
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} catch (MalformedURLException ex) {
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return null;
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} catch (URISyntaxException ex) {
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return null;
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}
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}
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/**
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* Takes a query string, separates the constituent name-value pairs, and
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* stores them in a SortedMap ordered by lexicographical order.
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*
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* @return Null if there is no query string.
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*/
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private static SortedMap<String, String> createParameterMap(final String queryString) {
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if (queryString == null || queryString.isEmpty()) {
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return null;
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}
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final String[] pairs = queryString.split("&");
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final Map<String, String> params = new HashMap<String, String>(pairs.length);
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for (final String pair : pairs) {
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if (pair.length() == 0) {
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continue;
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}
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String[] tokens = pair.split("=", 2);
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switch (tokens.length) {
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case 1:
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if (pair.charAt(0) == '=') {
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params.put("", tokens[0]);
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} else {
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params.put(tokens[0], "");
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}
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break;
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case 2:
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params.put(tokens[0], tokens[1]);
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break;
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}
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}
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return new TreeMap<String, String>(params);
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}
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/**
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* Canonicalize the query string.
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*
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* @param sortedParamMap
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* Parameter name-value pairs in lexicographical order.
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* @return Canonical form of query string.
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*/
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private static String canonicalize(final SortedMap<String, String> sortedParamMap) {
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if (sortedParamMap == null || sortedParamMap.isEmpty()) {
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return "";
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}
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final StringBuffer sb = new StringBuffer(100);
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for (Map.Entry<String, String> pair : sortedParamMap.entrySet()) {
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final String key = pair.getKey().toLowerCase();
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if (key.equals("jsessionid") || key.equals("phpsessid") || key.equals("aspsessionid")) {
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continue;
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}
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if (sb.length() > 0) {
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sb.append('&');
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}
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sb.append(percentEncodeRfc3986(pair.getKey()));
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if (!pair.getValue().isEmpty()) {
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sb.append('=');
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sb.append(percentEncodeRfc3986(pair.getValue()));
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}
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}
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return sb.toString();
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}
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/**
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* Percent-encode values according the RFC 3986. The built-in Java
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* URLEncoder does not encode according to the RFC, so we make the extra
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* replacements.
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*
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* @param string
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* Decoded string.
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* @return Encoded string per RFC 3986.
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*/
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private static String percentEncodeRfc3986(String string) {
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try {
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string = string.replace("+", "%2B");
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string = URLDecoder.decode(string, "UTF-8");
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string = URLEncoder.encode(string, "UTF-8");
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return string.replace("+", "%20").replace("*", "%2A").replace("%7E", "~");
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} catch (Exception e) {
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return string;
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}
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}
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private static String normalizePath(final String path) {
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return path.replace("%7E", "~").replace(" ", "%20");
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}
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}
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