Java tutorial
/* * Copyright (C) 2011 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.androidex.volley.toolbox; import android.graphics.Bitmap; import com.androidex.volley.Cache; import com.androidex.volley.NetworkResponse; import org.apache.http.impl.cookie.DateParseException; import org.apache.http.impl.cookie.DateUtils; import org.apache.http.protocol.HTTP; import java.io.ByteArrayOutputStream; import java.util.Map; /** * Utility methods for parsing HTTP headers. */ public class HttpHeaderParser { /** * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}. * * @param response The network response to parse headers from * @return a cache entry for the given response, or null if the response is not cacheable. */ public static Cache.Entry parseCacheHeaders(NetworkResponse response) { long now = System.currentTimeMillis(); long serverDate = 0; long serverExpires = 0; long softExpire = 0; long maxAge = 0; boolean hasCacheControl = false; Map<String, String> headers = null; String serverEtag = null; if (null != response) { headers = response.headers; String headerValue; headerValue = headers.get("Date"); if (headerValue != null) { serverDate = parseDateAsEpoch(headerValue); } headerValue = headers.get("Cache-Control"); if (headerValue != null) { hasCacheControl = true; String[] tokens = headerValue.split(","); for (int i = 0; i < tokens.length; i++) { String token = tokens[i].trim(); if (token.equals("no-cache") || token.equals("no-store")) { hasCacheControl = false; } else if (token.startsWith("max-age=")) { hasCacheControl = true; try { maxAge = Long.parseLong(token.substring(8)); } catch (Exception e) { } } else if (token.equals("must-revalidate") || token.equals("proxy-revalidate")) { maxAge = 0; } } } headerValue = headers.get("Expires"); if (headerValue != null) { serverExpires = parseDateAsEpoch(headerValue); } serverEtag = headers.get("ETag"); // Cache-Control takes precedence over an Expires header, even if both exist and Expires // is more restrictive. if (hasCacheControl) { softExpire = now + maxAge * 1000; } else if (serverDate > 0 && serverExpires >= serverDate) { // Default semantic for Expire header in HTTP specification is softExpire. softExpire = now + (serverExpires - serverDate); } } Cache.Entry entry = new Cache.Entry(); entry.data = response == null ? null : response.data; entry.etag = serverEtag; entry.softTtl = softExpire; entry.ttl = entry.softTtl; entry.serverDate = serverDate; entry.responseHeaders = headers; return entry; } /** * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}. * Cache-control headers are ignored. SoftTtl == 3 mins, ttl == 24 hours. * @param bitmap The network response to parse headers from * @return a cache entry for the given response, or null if the response is not cacheable. */ public static Cache.Entry parseBitmapCacheHeaders(Bitmap bitmap) { NetworkResponse response = null; if (null != bitmap) { ByteArrayOutputStream stream = new ByteArrayOutputStream(); bitmap.compress(Bitmap.CompressFormat.JPEG, 70, stream); byte[] byteArray = stream.toByteArray(); response = new NetworkResponse(byteArray); } return parseCacheHeaders(response); } /** * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}. * Cache-control headers are ignored. SoftTtl == 3 mins, ttl == 24 hours. * @param response The network response to parse headers from * @return a cache entry for the given response, or null if the response is not cacheable. */ public static Cache.Entry parseIgnoreCacheHeaders(NetworkResponse response) { long now = System.currentTimeMillis(); Map<String, String> headers = response.headers; long serverDate = 0; String serverEtag = null; String headerValue; headerValue = headers.get("Date"); if (headerValue != null) { serverDate = parseDateAsEpoch(headerValue); } serverEtag = headers.get("ETag"); final long cacheHitButRefreshed = 3 * 60 * 1000; // in 3 minutes cache will be hit, but also refreshed on background final long cacheExpired = 24 * 60 * 60 * 1000; // in 24 hours this cache entry expires completely final long softExpire = now + cacheHitButRefreshed; final long ttl = now + cacheExpired; Cache.Entry entry = new Cache.Entry(); entry.data = response.data; entry.etag = serverEtag; entry.softTtl = softExpire; entry.ttl = ttl; entry.serverDate = serverDate; entry.responseHeaders = headers; return entry; } /** * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}. * Cache-control headers are ignored. SoftTtl == 3 mins, ttl == 24 hours. * @param response The network response to parse headers from * @param soft_expire The soft expire duration in milli seconds * @param expire The full expire duration in milli seconds * @return a cache entry for the given response, or null if the response is not cacheable. */ public static Cache.Entry parseIgnoreCacheHeaders(NetworkResponse response, long soft_expire, long expire) { long now = System.currentTimeMillis(); Map<String, String> headers = response.headers; long serverDate = 0; String serverEtag = null; String headerValue; headerValue = headers.get("Date"); if (headerValue != null) { serverDate = parseDateAsEpoch(headerValue); } serverEtag = headers.get("ETag"); final long cacheHitButRefreshed = soft_expire; // in this duration cache will be hit, but also refreshed on background final long cacheExpired = expire; // in this duration this cache entry expires completely final long softExpire = now + cacheHitButRefreshed; final long ttl = now + cacheExpired; Cache.Entry entry = new Cache.Entry(); entry.data = response.data; entry.etag = serverEtag; entry.softTtl = softExpire; entry.ttl = ttl; entry.serverDate = serverDate; entry.responseHeaders = headers; return entry; } /** * Parse date in RFC1123 format, and return its value as epoch */ public static long parseDateAsEpoch(String dateStr) { try { // Parse date in RFC1123 format if this header contains one return DateUtils.parseDate(dateStr).getTime(); } catch (DateParseException e) { // Date in invalid format, fallback to 0 return 0; } } /** * Returns the charset specified in the Content-Type of this header, * or the HTTP default (ISO-8859-1) if none can be found. */ public static String parseCharset(Map<String, String> headers) { String contentType = headers.get(HTTP.CONTENT_TYPE); if (contentType != null) { String[] params = contentType.split(";"); for (int i = 1; i < params.length; i++) { String[] pair = params[i].trim().split("="); if (pair.length == 2) { if (pair[0].equals("charset")) { return pair[1]; } } } } return HTTP.DEFAULT_CONTENT_CHARSET; } }