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.selene.volley.tool; import android.os.SystemClock; import com.selene.volley.cache.Cache; import com.selene.volley.cache.Cache.Entry; import com.selene.volley.core.AuthFailureError; import com.selene.volley.core.Delivery; import com.selene.volley.core.Network; import com.selene.volley.core.NetworkError; import com.selene.volley.core.NetworkResponse; import com.selene.volley.core.NoConnectionError; import com.selene.volley.core.RedirectError; import com.selene.volley.core.Request; import com.selene.volley.core.RetryPolicy; import com.selene.volley.core.ServerError; import com.selene.volley.core.TimeoutError; import com.selene.volley.core.VolleyError; import com.selene.volley.core.VolleyLog; import com.selene.volley.stack.HttpStack; import org.apache.http.Header; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.HttpStatus; import org.apache.http.StatusLine; import org.apache.http.conn.ConnectTimeoutException; import org.apache.http.impl.cookie.DateUtils; import java.io.IOException; import java.io.InputStream; import java.net.MalformedURLException; import java.net.SocketTimeoutException; import java.util.Collections; import java.util.Date; import java.util.HashMap; import java.util.Map; import java.util.TreeMap; /** * A network performing VolleyPlus requests over an {@link HttpStack}. */ public class BasicNetwork implements Network { protected static final boolean DEBUG = VolleyLog.DEBUG; private static int SLOW_REQUEST_THRESHOLD_MS = 3000; private static int DEFAULT_POOL_SIZE = 4096; private final HttpStack mHttpStack; protected final ByteArrayPool mPool; /** Request delivery mechanism. */ private Delivery mDelivery; /** * @param httpStack * HTTP stack to be used */ public BasicNetwork(HttpStack httpStack) { // If a pool isn't passed in, then build a small default pool //that will give us a lot of benefit and not use too much memory. this(httpStack, new ByteArrayPool(DEFAULT_POOL_SIZE)); } /** * @param httpStack * HTTP stack to be used * @param pool * a buffer pool that improves GC performance in copy operations */ public BasicNetwork(HttpStack httpStack, ByteArrayPool pool) { mHttpStack = httpStack; mPool = pool; } @Override public void setDelivery(Delivery delivery) { mDelivery = delivery; } @Override public NetworkResponse performRequest(Request<?> request) throws VolleyError { // Determine if request had non-http perform. NetworkResponse networkResponse = request.perform(); if (networkResponse != null) { return networkResponse; } long requestStart = SystemClock.elapsedRealtime(); while (true) { // If the request was cancelled already, // do not perform the network request. if (request.isCanceled()) { request.finish("perform-discard-cancelled"); mDelivery.postCancel(request); throw new NetworkError(networkResponse); } HttpResponse httpResponse = null; byte[] responseContents = null; Map<String, String> responseHeaders = Collections.emptyMap(); try { // prepare to perform this request, normally is reset the request headers. request.prepare(); // Gather headers. Map<String, String> headers = new HashMap<String, String>(); addCacheHeaders(headers, request.getCacheEntry()); httpResponse = mHttpStack.performRequest(request, headers); StatusLine statusLine = httpResponse.getStatusLine(); int statusCode = statusLine.getStatusCode(); responseHeaders = convertHeaders(httpResponse.getAllHeaders()); responseContents = request.handleResponse(httpResponse, mDelivery); // Handle cache validation. if (statusCode == HttpStatus.SC_NOT_MODIFIED) { Entry entry = request.getCacheEntry(); if (entry == null) { return new NetworkResponse(HttpStatus.SC_NOT_MODIFIED, null, responseHeaders, true, SystemClock.elapsedRealtime() - requestStart); } // A HTTP 304 response does not have all header fields. We // have to use the header fields from the cache entry plus // the new ones from the response. // http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.5 entry.responseHeaders.putAll(responseHeaders); return new NetworkResponse(HttpStatus.SC_NOT_MODIFIED, entry.data, entry.responseHeaders, true, SystemClock.elapsedRealtime() - requestStart); } // Handle moved resources if (statusCode == HttpStatus.SC_MOVED_PERMANENTLY || statusCode == HttpStatus.SC_MOVED_TEMPORARILY) { String newUrl = responseHeaders.get("Location"); request.setRedirectUrl(newUrl); } // Some responses such as 204s do not have content. We must check. alternative by handleResponse // if (httpResponse.getEntity() != null) { // responseContents = entityToBytes(httpResponse.getEntity()); // } else { // // Add 0 byte response as a way of honestly representing a // // no-content request. // responseContents = new byte[0]; // } // if the request is slow, log it. long requestLifetime = SystemClock.elapsedRealtime() - requestStart; logSlowRequests(requestLifetime, request, responseContents, statusLine); if (statusCode < 200 || statusCode > 299) { throw new IOException(); } return new NetworkResponse(statusCode, responseContents, responseHeaders, false, SystemClock.elapsedRealtime() - requestStart); } catch (SocketTimeoutException e) { attemptRetryOnException("socket", request, new TimeoutError()); } catch (ConnectTimeoutException e) { attemptRetryOnException("connection", request, new TimeoutError()); } catch (MalformedURLException e) { throw new RuntimeException("Bad URL " + request.getUrl(), e); } catch (IOException e) { int statusCode = 0; if (httpResponse != null) { statusCode = httpResponse.getStatusLine().getStatusCode(); } else { throw new NoConnectionError(e); } if (statusCode == HttpStatus.SC_MOVED_PERMANENTLY || statusCode == HttpStatus.SC_MOVED_TEMPORARILY) { VolleyLog.e("Request at %s has been redirected to %s", request.getOriginUrl(), request.getUrl()); } else { VolleyLog.e("Unexpected response code %d for %s", statusCode, request.getUrl()); } if (responseContents != null) { networkResponse = new NetworkResponse(statusCode, responseContents, responseHeaders, false, SystemClock.elapsedRealtime() - requestStart); if (statusCode == HttpStatus.SC_UNAUTHORIZED || statusCode == HttpStatus.SC_FORBIDDEN) { attemptRetryOnException("auth", request, new AuthFailureError(networkResponse)); } else if (statusCode == HttpStatus.SC_MOVED_PERMANENTLY || statusCode == HttpStatus.SC_MOVED_TEMPORARILY) { attemptRetryOnException("redirect", request, new RedirectError(networkResponse)); } else { // TODO: Only throw ServerError for 5xx status codes. throw new ServerError(networkResponse); } } else { throw new NetworkError(networkResponse); } } } } /** * Logs requests that took over SLOW_REQUEST_THRESHOLD_MS to complete. */ private void logSlowRequests(long requestLifetime, Request<?> request, byte[] responseContents, StatusLine statusLine) { if (DEBUG || requestLifetime > SLOW_REQUEST_THRESHOLD_MS) { VolleyLog.d("HTTP response for request=<%s> [lifetime=%d], [size=%s], " + "[rc=%d], [retryCount=%s]", request, requestLifetime, responseContents != null ? responseContents.length : "null", statusLine.getStatusCode(), request.getRetryPolicy().getCurrentRetryCount()); } } /** * Attempts to prepare the request for a retry. If there are no more * attempts remaining in the request's retry policy, a timeout exception is * thrown. * * @param request * The request to use. */ private void attemptRetryOnException(String logPrefix, Request<?> request, VolleyError exception) throws VolleyError { RetryPolicy retryPolicy = request.getRetryPolicy(); int oldTimeout = request.getTimeoutMs(); try { retryPolicy.retry(exception); } catch (VolleyError e) { request.addMarker(String.format("%s-timeout-giveup [timeout=%s]", logPrefix, oldTimeout)); throw e; } request.addMarker(String.format("%s-retry [timeout=%s]", logPrefix, oldTimeout)); mDelivery.postRetry(request); } private void addCacheHeaders(Map<String, String> headers, Cache.Entry entry) { // If there's no cache entry, we're done. if (entry == null) { return; } if (entry.etag != null) { headers.put("If-None-Match", entry.etag); } if (entry.lastModified > 0) { Date refTime = new Date(entry.lastModified); headers.put("If-Modified-Since", DateUtils.formatDate(refTime)); } } protected void logError(String what, String url, long start) { long now = SystemClock.elapsedRealtime(); VolleyLog.v("HTTP ERROR(%s) %d ms to fetch %s", what, (now - start), url); } /** Reads the contents of HttpEntity into a byte[]. */ private byte[] entityToBytes(HttpEntity entity) throws IOException, ServerError { PoolingByteArrayOutputStream bytes = new PoolingByteArrayOutputStream(mPool, (int) entity.getContentLength()); byte[] buffer = null; try { InputStream in = entity.getContent(); if (in == null) { throw new ServerError(); } buffer = mPool.getBuf(1024); int count; while ((count = in.read(buffer)) != -1) { bytes.write(buffer, 0, count); } return bytes.toByteArray(); } finally { try { // Close the InputStream and release the resources by // "consuming the content". entity.consumeContent(); } catch (IOException e) { // This can happen if there was an exception above that left the // entity in // an invalid state. VolleyLog.v("Error occured when calling consumingContent"); } mPool.returnBuf(buffer); bytes.close(); } } /** * Converts Headers[] to Map<String, String>. */ protected static Map<String, String> convertHeaders(Header[] headers) { Map<String, String> result = new TreeMap<String, String>(String.CASE_INSENSITIVE_ORDER); for (int i = 0; i < headers.length; i++) { result.put(headers[i].getName(), headers[i].getValue()); } return result; } }