android/src/com/google/zxing/client/android/HttpHelper.java

/*
 * Copyright 2011 ZXing authors
 *
 * Licensed 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 com.google.zxing.client.android;

import android.util.Log;

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.HttpURLConnection;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;

/**
 * Utility methods for retrieving content over HTTP using the more-supported {@code java.net} classes
 * in Android.
 */
public final class HttpHelper {

  private static final String TAG = HttpHelper.class.getSimpleName();

  private static final Collection<String> REDIRECTOR_DOMAINS = new HashSet<>(Arrays.asList(
    "amzn.to", "bit.ly", "bitly.com", "fb.me", "goo.gl", "is.gd", "j.mp", "lnkd.in", "ow.ly",
    "R.BEETAGG.COM", "r.beetagg.com", "SCN.BY", "su.pr", "t.co", "tinyurl.com", "tr.im"
  ));

  private HttpHelper() {
  }

  /**
   * Enumeration of supported HTTP content types
   */
  public enum ContentType {
    /** HTML-like content type, including HTML, XHTML, etc. */
    HTML,
    /** JSON content */
    JSON,
    /** XML */
    XML,
    /** Plain text content */
    TEXT,
  }

  /**
   * Downloads the entire resource instead of part.
   *
   * @param uri URI to retrieve
   * @param type expected text-like MIME type of that content
   * @return content as a {@code String}
   * @throws IOException if the content can't be retrieved because of a bad URI, network problem, etc.
   * @see #downloadViaHttp(String, HttpHelper.ContentType, int)
   */
  public static CharSequence downloadViaHttp(String uri, ContentType type) throws IOException {
    return downloadViaHttp(uri, type, Integer.MAX_VALUE);
  }

  /**
   * @param uri URI to retrieve
   * @param type expected text-like MIME type of that content
   * @param maxChars approximate maximum characters to read from the source
   * @return content as a {@code String}
   * @throws IOException if the content can't be retrieved because of a bad URI, network problem, etc.
   */
  public static CharSequence downloadViaHttp(String uri, ContentType type, int maxChars) throws IOException {
    String contentTypes;
    switch (type) {
      case HTML:
        contentTypes = "application/xhtml+xml,text/html,text/*,*/*";
        break;
      case JSON:
        contentTypes = "application/json,text/*,*/*";
        break;
      case XML:
        contentTypes = "application/xml,text/*,*/*";
        break;
      default: // Includes TEXT
        contentTypes = "text/*,*/*";
    }
    return downloadViaHttp(uri, contentTypes, maxChars);
  }

  private static CharSequence downloadViaHttp(String uri, String contentTypes, int maxChars) throws IOException {
    int redirects = 0;
    while (redirects < 5) {
      URL url = new URL(uri);
      HttpURLConnection connection = safelyOpenConnection(url);
      connection.setInstanceFollowRedirects(true); // Won't work HTTP -> HTTPS or vice versa
      connection.setRequestProperty("Accept", contentTypes);
      connection.setRequestProperty("Accept-Charset", "utf-8,*");
      connection.setRequestProperty("User-Agent", "ZXing (Android)");
      try {
        int responseCode = safelyConnect(connection);
        switch (responseCode) {
          case HttpURLConnection.HTTP_OK:
            return consume(connection, maxChars);
          case HttpURLConnection.HTTP_MOVED_TEMP:
            String location = connection.getHeaderField("Location");
            if (location != null) {
              uri = location;
              redirects++;
              continue;
            }
            throw new IOException("No Location");
          default:
            throw new IOException("Bad HTTP response: " + responseCode);
        }
      } finally {
        connection.disconnect();
      }
    }
    throw new IOException("Too many redirects");
  }

  private static String getEncoding(URLConnection connection) {
    String contentTypeHeader = connection.getHeaderField("Content-Type");
    if (contentTypeHeader != null) {
      int charsetStart = contentTypeHeader.indexOf("charset=");
      if (charsetStart >= 0) {
        return contentTypeHeader.substring(charsetStart + "charset=".length());
      }
    }
    return "UTF-8";
  }

  private static CharSequence consume(URLConnection connection, int maxChars) throws IOException {
    String encoding = getEncoding(connection);
    StringBuilder out = new StringBuilder();
    try (Reader in = new InputStreamReader(connection.getInputStream(), encoding)) {
      char[] buffer = new char[1024];
      int charsRead;
      while (out.length() < maxChars && (charsRead = in.read(buffer)) > 0) {
        out.append(buffer, 0, charsRead);
      }
    }
    return out;
  }

  public static URI unredirect(URI uri) throws IOException {
    if (!REDIRECTOR_DOMAINS.contains(uri.getHost())) {
      return uri;
    }
    URL url = uri.toURL();
    HttpURLConnection connection = safelyOpenConnection(url);
    connection.setInstanceFollowRedirects(false);
    connection.setDoInput(false);
    connection.setRequestMethod("HEAD");
    connection.setRequestProperty("User-Agent", "ZXing (Android)");
    try {
      int responseCode = safelyConnect(connection);
      switch (responseCode) {
        case HttpURLConnection.HTTP_MULT_CHOICE:
        case HttpURLConnection.HTTP_MOVED_PERM:
        case HttpURLConnection.HTTP_MOVED_TEMP:
        case HttpURLConnection.HTTP_SEE_OTHER:
        case 307: // No constant for 307 Temporary Redirect ?
          String location = connection.getHeaderField("Location");
          if (location != null) {
            try {
              return new URI(location);
            } catch (URISyntaxException e) {
              // nevermind
            }
          }
      }
      return uri;
    } finally {
      connection.disconnect();
    }
  }
  
  private static HttpURLConnection safelyOpenConnection(URL url) throws IOException {
    URLConnection conn;
    try {
      conn = url.openConnection();
    } catch (NullPointerException npe) {
      // Another strange bug in Android?
      Log.w(TAG, "Bad URI? " + url);
      throw new IOException(npe);
    }
    if (!(conn instanceof HttpURLConnection)) {
      throw new IOException();
    }
    return (HttpURLConnection) conn;
  }

  private static int safelyConnect(HttpURLConnection connection) throws IOException {
    try {
      connection.connect();
    } catch (RuntimeException e) {
      // These are, generally, Android bugs
      throw new IOException(e);
    }
    try {
      return connection.getResponseCode();
    } catch (NullPointerException | StringIndexOutOfBoundsException | IllegalArgumentException e) {
      // this is maybe this Android bug: http://code.google.com/p/android/issues/detail?id=15554
      throw new IOException(e);
    }
  }

}