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/*
* Copyright (C) 2015 The Android Open Source Project
*
* 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.android.statementservice.retriever;
import android.util.Log;
import com.android.volley.Cache;
import com.android.volley.NetworkResponse;
import com.android.volley.toolbox.HttpHeaderParser;
import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
/**
* Helper class for fetching HTTP or HTTPS URL.
*
* Visible for testing.
*
* @hide
*/
public class URLFetcher {
private static final String TAG = URLFetcher.class.getSimpleName();
private static final long DO_NOT_CACHE_RESULT = 0L;
private static final int INPUT_BUFFER_SIZE_IN_BYTES = 1024;
/**
* Fetches the specified url and returns the content and ttl.
*
* @throws IOException if it can't retrieve the content due to a network problem.
* @throws AssociationServiceException if the URL scheme is not http or https or the content
* length exceeds {code fileSizeLimit}.
*/
public WebContent getWebContentFromUrl(URL url, long fileSizeLimit, int connectionTimeoutMillis)
throws AssociationServiceException, IOException {
final String scheme = url.getProtocol().toLowerCase(Locale.US);
if (!scheme.equals("http") && !scheme.equals("https")) {
throw new IllegalArgumentException("The url protocol should be on http or https.");
}
HttpURLConnection connection = null;
try {
connection = (HttpURLConnection) url.openConnection();
connection.setInstanceFollowRedirects(true);
connection.setConnectTimeout(connectionTimeoutMillis);
connection.setReadTimeout(connectionTimeoutMillis);
connection.setUseCaches(true);
connection.setInstanceFollowRedirects(false);
connection.addRequestProperty("Cache-Control", "max-stale=60");
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
Log.e(TAG, "The responses code is not 200 but " + connection.getResponseCode());
return new WebContent("", DO_NOT_CACHE_RESULT);
}
if (connection.getContentLength() > fileSizeLimit) {
Log.e(TAG, "The content size of the url is larger than " + fileSizeLimit);
return new WebContent("", DO_NOT_CACHE_RESULT);
}
Long expireTimeMillis = getExpirationTimeMillisFromHTTPHeader(
connection.getHeaderFields());
return new WebContent(inputStreamToString(
connection.getInputStream(), connection.getContentLength(), fileSizeLimit),
expireTimeMillis);
} finally {
if (connection != null) {
connection.disconnect();
}
}
}
/**
* Visible for testing.
* @hide
*/
public static String inputStreamToString(InputStream inputStream, int length, long sizeLimit)
throws IOException, AssociationServiceException {
if (length < 0) {
length = 0;
}
ByteArrayOutputStream baos = new ByteArrayOutputStream(length);
BufferedInputStream bis = new BufferedInputStream(inputStream);
byte[] buffer = new byte[INPUT_BUFFER_SIZE_IN_BYTES];
int len = 0;
while ((len = bis.read(buffer)) != -1) {
baos.write(buffer, 0, len);
if (baos.size() > sizeLimit) {
throw new AssociationServiceException("The content size of the url is larger than "
+ sizeLimit);
}
}
return baos.toString("UTF-8");
}
/**
* Parses the HTTP headers to compute the ttl.
*
* @param headers a map that map the header key to the header values. Can be null.
* @return the ttl in millisecond or null if the ttl is not specified in the header.
*/
private Long getExpirationTimeMillisFromHTTPHeader(Map<String, List<String>> headers) {
if (headers == null) {
return null;
}
Map<String, String> joinedHeaders = joinHttpHeaders(headers);
NetworkResponse response = new NetworkResponse(null, joinedHeaders);
Cache.Entry cachePolicy = HttpHeaderParser.parseCacheHeaders(response);
if (cachePolicy == null) {
// Cache is disabled, set the expire time to 0.
return DO_NOT_CACHE_RESULT;
} else if (cachePolicy.ttl == 0) {
// Cache policy is not specified, set the expire time to 0.
return DO_NOT_CACHE_RESULT;
} else {
// cachePolicy.ttl is actually the expire timestamp in millisecond.
return cachePolicy.ttl;
}
}
/**
* Converts an HTTP header map of the format provided by {@linkHttpUrlConnection} to a map of
* the format accepted by {@link HttpHeaderParser}. It does this by joining all the entries for
* a given header key with ", ".
*/
private Map<String, String> joinHttpHeaders(Map<String, List<String>> headers) {
Map<String, String> joinedHeaders = new HashMap<String, String>();
for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
List<String> values = entry.getValue();
if (values.size() == 1) {
joinedHeaders.put(entry.getKey(), values.get(0));
} else {
joinedHeaders.put(entry.getKey(), Utils.joinStrings(", ", values));
}
}
return joinedHeaders;
}
}
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