1 | /* |
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2 | * HttpHead.java |
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3 | * |
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4 | * Copyright (C) 2010 Mark Evenson |
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5 | * $Id: HttpHead.java 14627 2014-02-16 21:25:20Z mevenson $ |
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6 | * |
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7 | * This program is free software; you can redistribute it and/or |
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8 | * modify it under the terms of the GNU General Public License |
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9 | * as published by the Free Software Foundation; either version 2 |
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10 | * of the License, or (at your option) any later version. |
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11 | * |
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12 | * This program is distributed in the hope that it will be useful, |
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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15 | * GNU General Public License for more details. |
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16 | * |
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17 | * You should have received a copy of the GNU General Public License |
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18 | * along with this program; if not, write to the Free Software |
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19 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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20 | * |
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21 | * As a special exception, the copyright holders of this library give you |
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22 | * permission to link this library with independent modules to produce an |
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23 | * executable, regardless of the license terms of these independent |
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24 | * modules, and to copy and distribute the resulting executable under |
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25 | * terms of your choice, provided that you also meet, for each linked |
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26 | * independent module, the terms and conditions of the license of that |
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27 | * module. An independent module is a module which is not derived from |
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28 | * or based on this library. If you modify this library, you may extend |
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29 | * this exception to your version of the library, but you are not |
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30 | * obligated to do so. If you do not wish to do so, delete this |
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31 | * exception statement from your version. |
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32 | */ |
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33 | package org.armedbear.lisp.util; |
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34 | |
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35 | import org.armedbear.lisp.Debug; |
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36 | |
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37 | import java.io.BufferedReader; |
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38 | import java.io.IOException; |
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39 | import java.io.InputStreamReader; |
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40 | import java.io.OutputStreamWriter; |
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41 | import java.io.PrintWriter; |
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42 | import java.net.InetSocketAddress; |
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43 | import java.net.MalformedURLException; |
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44 | import java.net.Proxy; |
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45 | import java.net.Socket; |
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46 | import java.net.URL; |
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47 | |
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48 | /** |
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49 | * Use HTTP/1.1 HEAD to retrieve the specified header field. |
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50 | */ |
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51 | public class HttpHead { |
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52 | static private String get(String urlString, String key) throws IOException { |
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53 | URL url = null; |
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54 | try { |
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55 | url = new URL(urlString); |
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56 | } catch (MalformedURLException e) { |
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57 | log("Failed to form url from " + "'" + urlString + "'" + ": " + e); |
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58 | } |
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59 | return get(url, key); |
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60 | } |
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61 | |
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62 | static public String get(URL url, String key) throws IOException { |
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63 | Socket socket = null; |
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64 | String result = null; |
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65 | try { |
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66 | String protocol = url.getProtocol(); |
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67 | if (!protocol.equals("http")) { |
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68 | log("The protocol " + "'" + protocol + "'" + " is not http."); |
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69 | return result; |
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70 | } |
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71 | String host = url.getHost(); |
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72 | int port = url.getPort(); |
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73 | if (port == -1) { |
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74 | port = 80; |
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75 | } |
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76 | socket = new Socket(host, port); |
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77 | |
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78 | PrintWriter out = null; |
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79 | BufferedReader in = null; |
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80 | try { |
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81 | socket.setSoTimeout(5000); // ms |
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82 | out = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()), true); |
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83 | in = new BufferedReader(new InputStreamReader(socket.getInputStream())); |
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84 | } catch (IOException e) { |
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85 | log("Failed to establish socket io: " + e); |
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86 | return result; |
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87 | } |
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88 | |
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89 | String CRLF = "\r\n"; |
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90 | String head = "HEAD " + url.getPath() + " HTTP/1.1"; |
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91 | out.print(head + CRLF); |
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92 | out.print("Host: " + url.getAuthority() + CRLF); |
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93 | out.print("Connection: close" + CRLF); |
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94 | out.print(CRLF); |
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95 | out.flush(); |
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96 | |
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97 | String line = null; |
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98 | try { |
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99 | line = in.readLine(); |
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100 | } catch (IOException e) { |
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101 | log("Failed to read HTTP response: " + e); |
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102 | } |
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103 | if (line == null) { |
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104 | throw new IOException("Could not access URL to parse headers."); |
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105 | } |
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106 | String status[] = line.split("\\s"); |
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107 | if (status[1].equals("200")) { |
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108 | result = findHeader(in, key); |
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109 | } else if (status[1].startsWith("3")) { |
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110 | // Follow redirects ad nauseum |
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111 | String location = findHeader(in, "Location"); |
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112 | if (location != null) { |
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113 | return get(location, key); |
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114 | } |
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115 | } else { |
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116 | log("Unexpected response: " + line); |
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117 | } |
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118 | } finally { |
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119 | try { |
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120 | socket.close(); |
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121 | } catch (IOException e) { |
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122 | } |
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123 | } |
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124 | return result; |
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125 | } |
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126 | |
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127 | static private String findHeader(BufferedReader in, String key) { |
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128 | String result = null; |
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129 | String line; |
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130 | try { |
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131 | while ((line = in.readLine()) != null) { |
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132 | int i = line.indexOf(":"); |
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133 | if (i == -1) { |
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134 | continue; // XXX parse multi-line HTTP headers |
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135 | } |
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136 | String k = line.substring(0, i); |
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137 | String v = line.substring(i + 1).trim(); |
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138 | if (k.equals(key)) { |
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139 | result = v; |
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140 | break; |
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141 | } |
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142 | } |
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143 | } catch (IOException e) { |
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144 | log("Failed to read headers: " + e); |
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145 | } |
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146 | return result; |
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147 | } |
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148 | |
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149 | static private void log(String message) { |
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150 | Debug.warn(message); |
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151 | } |
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152 | |
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153 | public static void main(String argv[]) { |
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154 | if (argv.length != 1) { |
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155 | System.out.println("Usage: <cmd> URL"); |
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156 | return; |
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157 | } |
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158 | String modified = null; |
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159 | try { |
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160 | modified = get(argv[0], "Last-Modified"); |
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161 | } catch (IOException ex) { |
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162 | System.err.println("Unable to get Last-Modified header: "); |
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163 | ex.printStackTrace(System.err); |
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164 | } |
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165 | if (modified != null) { |
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166 | System.out.println("Last-Modified: " + modified); |
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167 | } else { |
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168 | System.out.println("No result returned."); |
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169 | } |
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170 | } |
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171 | } |
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