1/*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.volley;
18
19import android.net.TrafficStats;
20import android.os.Build;
21import android.os.Process;
22
23import java.util.concurrent.BlockingQueue;
24
25/**
26 * Provides a thread for performing network dispatch from a queue of requests.
27 *
28 * Requests added to the specified queue are processed from the network via a
29 * specified {@link Network} interface. Responses are committed to cache, if
30 * eligible, using a specified {@link Cache} interface. Valid responses and
31 * errors are posted back to the caller via a {@link ResponseDelivery}.
32 */
33@SuppressWarnings("rawtypes")
34public class NetworkDispatcher extends Thread {
35    /** The queue of requests to service. */
36    private final BlockingQueue<Request> mQueue;
37    /** The network interface for processing requests. */
38    private final Network mNetwork;
39    /** The cache to write to. */
40    private final Cache mCache;
41    /** For posting responses and errors. */
42    private final ResponseDelivery mDelivery;
43    /** Used for telling us to die. */
44    private volatile boolean mQuit = false;
45
46    /**
47     * Creates a new network dispatcher thread.  You must call {@link #start()}
48     * in order to begin processing.
49     *
50     * @param queue Queue of incoming requests for triage
51     * @param network Network interface to use for performing requests
52     * @param cache Cache interface to use for writing responses to cache
53     * @param delivery Delivery interface to use for posting responses
54     */
55    public NetworkDispatcher(BlockingQueue<Request> queue,
56            Network network, Cache cache,
57            ResponseDelivery delivery) {
58        mQueue = queue;
59        mNetwork = network;
60        mCache = cache;
61        mDelivery = delivery;
62    }
63
64    /**
65     * Forces this dispatcher to quit immediately.  If any requests are still in
66     * the queue, they are not guaranteed to be processed.
67     */
68    public void quit() {
69        mQuit = true;
70        interrupt();
71    }
72
73    @Override
74    public void run() {
75        Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
76        Request request;
77        while (true) {
78            try {
79                // Take a request from the queue.
80                request = mQueue.take();
81            } catch (InterruptedException e) {
82                // We may have been interrupted because it was time to quit.
83                if (mQuit) {
84                    return;
85                }
86                continue;
87            }
88
89            try {
90                request.addMarker("network-queue-take");
91
92                // If the request was cancelled already, do not perform the
93                // network request.
94                if (request.isCanceled()) {
95                    request.finish("network-discard-cancelled");
96                    continue;
97                }
98
99                // Tag the request (if API >= 14)
100                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
101                    TrafficStats.setThreadStatsTag(request.getTrafficStatsTag());
102                }
103
104                // Perform the network request.
105                NetworkResponse networkResponse = mNetwork.performRequest(request);
106                request.addMarker("network-http-complete");
107
108                // If the server returned 304 AND we delivered a response already,
109                // we're done -- don't deliver a second identical response.
110                if (networkResponse.notModified && request.hasHadResponseDelivered()) {
111                    request.finish("not-modified");
112                    continue;
113                }
114
115                // Parse the response here on the worker thread.
116                Response<?> response = request.parseNetworkResponse(networkResponse);
117                request.addMarker("network-parse-complete");
118
119                // Write to cache if applicable.
120                // TODO: Only update cache metadata instead of entire record for 304s.
121                if (request.shouldCache() && response.cacheEntry != null) {
122                    mCache.put(request.getCacheKey(), response.cacheEntry);
123                    request.addMarker("network-cache-written");
124                }
125
126                // Post the response back.
127                request.markDelivered();
128                mDelivery.postResponse(request, response);
129            } catch (VolleyError volleyError) {
130                parseAndDeliverNetworkError(request, volleyError);
131            } catch (Exception e) {
132                VolleyLog.e(e, "Unhandled exception %s", e.toString());
133                mDelivery.postError(request, new VolleyError(e));
134            }
135        }
136    }
137
138    private void parseAndDeliverNetworkError(Request<?> request, VolleyError error) {
139        error = request.parseNetworkError(error);
140        mDelivery.postError(request, error);
141    }
142}
143