本文是基于Volley 1.1.0的源码分析
Volley类
public class Volley {
/** Default on-disk cache directory. */
private static final String DEFAULT_CACHE_DIR = "volley";
/**
* Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it.
*
* @param context A {@link Context} to use for creating the cache dir.
* @param stack A {@link BaseHttpStack} to use for the network, or null for default.
* @return A started {@link RequestQueue} instance.
*/
public static RequestQueue newRequestQueue(Context context, BaseHttpStack stack) {
BasicNetwork network;
if (stack == null) {
if (Build.VERSION.SDK_INT >= 9) {
network = new BasicNetwork(new HurlStack());
} else {
// Prior to Gingerbread, HttpUrlConnection was unreliable.
// See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html
// At some point in the future we'll move our minSdkVersion past Froyo and can
// delete this fallback (along with all Apache HTTP code).
String userAgent = "volley/0";
try {
String packageName = context.getPackageName();
PackageInfo info = context.getPackageManager().getPackageInfo(packageName, 0);
userAgent = packageName + "/" + info.versionCode;
} catch (NameNotFoundException e) {
}
network = new BasicNetwork(
new HttpClientStack(AndroidHttpClient.newInstance(userAgent)));
}
} else {
network = new BasicNetwork(stack);
}
return newRequestQueue(context, network);
}
/**
* Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it.
*
* @param context A {@link Context} to use for creating the cache dir.
* @param stack An {@link HttpStack} to use for the network, or null for default.
* @return A started {@link RequestQueue} instance.
* @deprecated Use {@link #newRequestQueue(Context, BaseHttpStack)} instead to avoid depending
* on Apache HTTP. This method may be removed in a future release of Volley.
*/
@Deprecated
@SuppressWarnings("deprecation")
public static RequestQueue newRequestQueue(Context context, HttpStack stack) {
if (stack == null) {
return newRequestQueue(context, (BaseHttpStack) null);
}
return newRequestQueue(context, new BasicNetwork(stack));
}
private static RequestQueue newRequestQueue(Context context, Network network) {
File cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR);
RequestQueue queue = new RequestQueue(new DiskBasedCache(cacheDir), network);
queue.start();
return queue;
}
/**
* Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it.
*
* @param context A {@link Context} to use for creating the cache dir.
* @return A started {@link RequestQueue} instance.
*/
public static RequestQueue newRequestQueue(Context context) {
return newRequestQueue(context, (BaseHttpStack) null);
}
}
Volley类里主要是静态方法newRequestQueue的重载
public static RequestQueue newRequestQueue(Context context, BaseHttpStack stack)
public static RequestQueue newRequestQueue(Context context, HttpStack stack)
public static RequestQueue newRequestQueue(Context context)
private static RequestQueue newRequestQueue(Context context, Network network)
其中第二个方法已经被废弃， 在以后的版本中可能被移除
废弃的原因是依赖了Apache HTTP，而Apache HTTP 在android6.0之后被移除了。
我们先来看看下面这个方法
/**
* Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it.
*
* @param context A {@link Context} to use for creating the cache dir.
* @return A started {@link RequestQueue} instance.
*/
public static RequestQueue newRequestQueue(Context context) {
return newRequestQueue(context, (BaseHttpStack) null);
}
上面这个方法实际执行的四个静态方法中的第一个。
再来看第一个方法
/**
* Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it.
*
* @param context A {@link Context} to use for creating the cache dir.
* @param stack A {@link BaseHttpStack} to use for the network, or null for default.
* @return A started {@link RequestQueue} instance.
*/
public static RequestQueue newRequestQueue(Context context, BaseHttpStack stack) {
BasicNetwork network;
if (stack == null) {
if (Build.VERSION.SDK_INT >= 9) {
network = new BasicNetwork(new HurlStack());
} else {
// Prior to Gingerbread, HttpUrlConnection was unreliable.
// See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html
// At some point in the future we'll move our minSdkVersion past Froyo and can
// delete this fallback (along with all Apache HTTP code).
String userAgent = "volley/0";
try {
String packageName = context.getPackageName();
PackageInfo info = context.getPackageManager().getPackageInfo(packageName, 0);
userAgent = packageName + "/" + info.versionCode;
} catch (NameNotFoundException e) {
}
network = new BasicNetwork(
new HttpClientStack(AndroidHttpClient.newInstance(userAgent)));
}
} else {
network = new BasicNetwork(stack);
}
return newRequestQueue(context, network);
}
当stack为空时，会根据android系统版本来决定使用哪种http框架
当android系统大于等于9， 默认使用URLConnection
当android系统小于9，默认使用Apache http client
这里区分android版本的原因是因为在android9以下，URLconnection有个bug
当stack不为空时，会根据给定的stack的实现类来决定使用什么http框架
这里我们可以实现一个基于okhttp的stack 让Volley支持okhttp
执行完判断逻辑后会创建一个BasicNetwork对象
然后执行私有的静态方法
private static RequestQueue newRequestQueue(Context context, Network network) {
File cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR);
RequestQueue queue = new RequestQueue(new DiskBasedCache(cacheDir), network);
queue.start();
return queue;
}
在这个私有静态方法中会创建一个RequestQueue ，并且调用它的start方法启动队列
之后我们创建的请求添加到这个队列中被执行
RequestQueue
/**
* A request dispatch queue with a thread pool of dispatchers.
*
* Calling {@link #add(Request)} will enqueue the given Request for dispatch,
* resolving from either cache or network on a worker thread, and then delivering
* a parsed response on the main thread.
*/
public class RequestQueue {
/** Callback interface for completed requests. */
public interface RequestFinishedListener {
/** Called when a request has finished processing. */
void onRequestFinished(Request request);
}
/** Used for generating monotonically-increasing sequence numbers for requests. */
private final AtomicInteger mSequenceGenerator = new AtomicInteger();
/**
* The set of all requests currently being processed by this RequestQueue. A Request
* will be in this set if it is waiting in any queue or currently being processed by
* any dispatcher.
*/
private final Set> mCurrentRequests = new HashSet>();
/** The cache triage queue. */
private final PriorityBlockingQueue> mCacheQueue =
new PriorityBlockingQueue<>();
/** The queue of requests that are actually going out to the network. */
private final PriorityBlockingQueue> mNetworkQueue =
new PriorityBlockingQueue<>();
/** Number of network request dispatcher threads to start. */
private static final int DEFAULT_NETWORK_THREAD_POOL_SIZE = 4;
/** Cache interface for retrieving and storing responses. */
private final Cache mCache;
/** Network interface for performing requests. */
private final Network mNetwork;
/** Response delivery mechanism. */
private final ResponseDelivery mDelivery;
/** The network dispatchers. */
private final NetworkDispatcher[] mDispatchers;
/** The cache dispatcher. */
private CacheDispatcher mCacheDispatcher;
private final List mFinishedListeners =
new ArrayList<>();
/**
* Creates the worker pool. Processing will not begin until {@link #start()} is called.
*
* @param cache A Cache to use for persisting responses to disk
* @param network A Network interface for performing HTTP requests
* @param threadPoolSize Number of network dispatcher threads to create
* @param delivery A ResponseDelivery interface for posting responses and errors
*/
public RequestQueue(Cache cache, Network network, int threadPoolSize,
ResponseDelivery delivery) {
mCache = cache;
mNetwork = network;
mDispatchers = new NetworkDispatcher[threadPoolSize];
mDelivery = delivery;
}
/**
* Creates the worker pool. Processing will not begin until {@link #start()} is called.
*
* @param cache A Cache to use for persisting responses to disk
* @param network A Network interface for performing HTTP requests
* @param threadPoolSize Number of network dispatcher threads to create
*/
public RequestQueue(Cache cache, Network network, int threadPoolSize) {
this(cache, network, threadPoolSize,
new ExecutorDelivery(new Handler(Looper.getMainLooper())));
}
/**
* Creates the worker pool. Processing will not begin until {@link #start()} is called.
*
* @param cache A Cache to use for persisting responses to disk
* @param network A Network interface for performing HTTP requests
*/
public RequestQueue(Cache cache, Network network) {
this(cache, network, DEFAULT_NETWORK_THREAD_POOL_SIZE);
}
/**
* Starts the dispatchers in this queue.
*/
public void start() {
stop(); // Make sure any currently running dispatchers are stopped.
// Create the cache dispatcher and start it.
mCacheDispatcher = new CacheDispatcher(mCacheQueue, mNetworkQueue, mCache, mDelivery);
mCacheDispatcher.start();
// Create network dispatchers (and corresponding threads) up to the pool size.
for (int i = 0; i < mDispatchers.length; i++) {
NetworkDispatcher networkDispatcher = new NetworkDispatcher(mNetworkQueue, mNetwork,
mCache, mDelivery);
mDispatchers[i] = networkDispatcher;
networkDispatcher.start();
}
}
/**
* Stops the cache and network dispatchers.
*/
public void stop() {
if (mCacheDispatcher != null) {
mCacheDispatcher.quit();
}
for (final NetworkDispatcher mDispatcher : mDispatchers) {
if (mDispatcher != null) {
mDispatcher.quit();
}
}
}
/**
* Gets a sequence number.
*/
public int getSequenceNumber() {
return mSequenceGenerator.incrementAndGet();
}
/**
* Gets the {@link Cache} instance being used.
*/
public Cache getCache() {
return mCache;
}
/**
* A simple predicate or filter interface for Requests, for use by
* {@link RequestQueue#cancelAll(RequestFilter)}.
*/
public interface RequestFilter {
boolean apply(Request request);
}
/**
* Cancels all requests in this queue for which the given filter applies.
* @param filter The filtering function to use
*/
public void cancelAll(RequestFilter filter) {
synchronized (mCurrentRequests) {
for (Request request : mCurrentRequests) {
if (filter.apply(request)) {
request.cancel();
}
}
}
}
/**
* Cancels all requests in this queue with the given tag. Tag must be non-null
* and equality is by identity.
*/
public void cancelAll(final Object tag) {
if (tag == null) {
throw new IllegalArgumentException("Cannot cancelAll with a null tag");
}
cancelAll(new RequestFilter() {
@Override
public boolean apply(Request request) {
return request.getTag() == tag;
}
});
}
/**
* Adds a Request to the dispatch queue.
* @param request The request to service
* @return The passed-in request
*/
public Request add(Request request) {
// Tag the request as belonging to this queue and add it to the set of current requests.
request.setRequestQueue(this);
synchronized (mCurrentRequests) {
mCurrentRequests.add(request);
}
// Process requests in the order they are added.
request.setSequence(getSequenceNumber());
request.addMarker("add-to-queue");
// If the request is uncacheable, skip the cache queue and go straight to the network.
if (!request.shouldCache()) {
mNetworkQueue.add(request);
return request;
}
mCacheQueue.add(request);
return request;
}
/**
* Called from {@link Request#finish(String)}, indicating that processing of the given request
* has finished.
*/
void finish(Request request) {
// Remove from the set of requests currently being processed.
synchronized (mCurrentRequests) {
mCurrentRequests.remove(request);
}
synchronized (mFinishedListeners) {
for (RequestFinishedListener listener : mFinishedListeners) {
listener.onRequestFinished(request);
}
}
}
public void addRequestFinishedListener(RequestFinishedListener listener) {
synchronized (mFinishedListeners) {
mFinishedListeners.add(listener);
}
}
/**
* Remove a RequestFinishedListener. Has no effect if listener was not previously added.
*/
public void removeRequestFinishedListener(RequestFinishedListener listener) {
synchronized (mFinishedListeners) {
mFinishedListeners.remove(listener);
}
}
}
我们先来分析一下RequestQueue的start方法
/**
* Starts the dispatchers in this queue.
*/
public void start() {
stop(); // Make sure any currently running dispatchers are stopped.
// Create the cache dispatcher and start it.
mCacheDispatcher = new CacheDispatcher(mCacheQueue, mNetworkQueue, mCache, mDelivery);
mCacheDispatcher.start();
// Create network dispatchers (and corresponding threads) up to the pool size.
for (int i = 0; i < mDispatchers.length; i++) {
NetworkDispatcher networkDispatcher = new NetworkDispatcher(mNetworkQueue, mNetwork,
mCache, mDelivery);
mDispatchers[i] = networkDispatcher;
networkDispatcher.start();
}
}
当队列启动后，会先调用stop方法 确保当前运行的dispatcher都停止了
接下来创建一个CacheDispatcher并启动
然后根据构造方法指定的线程数量创建指定数量的NetworkDispatcher并启动
CacherDispatcher和NetworkDispatcher都是继承Thread。
这样我们的线程池和缓存线程就都运行起来了。
再来看看add方法
/**
* Adds a Request to the dispatch queue.
* @param request The request to service
* @return The passed-in request
*/
public Request add(Request request) {
// Tag the request as belonging to this queue and add it to the set of current requests.
request.setRequestQueue(this);
synchronized (mCurrentRequests) {
mCurrentRequests.add(request);
}
// Process requests in the order they are added.
request.setSequence(getSequenceNumber());
request.addMarker("add-to-queue");
// If the request is uncacheable, skip the cache queue and go straight to the network.
if (!request.shouldCache()) {
mNetworkQueue.add(request);
return request;
}
mCacheQueue.add(request);
return request;
}
RequestQueue会添加自定义的Request到分发队列。
本质上是把Request放到一个set集合中
并给Request设置序号
接下来判断request是否需要缓存，如果不需要缓存 把request加到NetworkQueue中。
如果需要缓存把request加到CacheQueue中
这样request就会被线程执行。
NetworkDispatcher
/**
* Provides a thread for performing network dispatch from a queue of requests.
*
* Requests added to the specified queue are processed from the network via a
* specified {@link Network} interface. Responses are committed to cache, if
* eligible, using a specified {@link Cache} interface. Valid responses and
* errors are posted back to the caller via a {@link ResponseDelivery}.
*/
public class NetworkDispatcher extends Thread {
/** The queue of requests to service. */
private final BlockingQueue> mQueue;
/** The network interface for processing requests. */
private final Network mNetwork;
/** The cache to write to. */
private final Cache mCache;
/** For posting responses and errors. */
private final ResponseDelivery mDelivery;
/** Used for telling us to die. */
private volatile boolean mQuit = false;
/**
* Creates a new network dispatcher thread. You must call {@link #start()}
* in order to begin processing.
*
* @param queue Queue of incoming requests for triage
* @param network Network interface to use for performing requests
* @param cache Cache interface to use for writing responses to cache
* @param delivery Delivery interface to use for posting responses
*/
public NetworkDispatcher(BlockingQueue> queue,
Network network, Cache cache, ResponseDelivery delivery) {
mQueue = queue;
mNetwork = network;
mCache = cache;
mDelivery = delivery;
}
/**
* Forces this dispatcher to quit immediately. If any requests are still in
* the queue, they are not guaranteed to be processed.
*/
public void quit() {
mQuit = true;
interrupt();
}
@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
private void addTrafficStatsTag(Request request) {
// Tag the request (if API >= 14)
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
TrafficStats.setThreadStatsTag(request.getTrafficStatsTag());
}
}
@Override
public void run() {
Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
while (true) {
try {
processRequest();
} catch (InterruptedException e) {
// We may have been interrupted because it was time to quit.
if (mQuit) {
return;
}
}
}
}
// Extracted to its own method to ensure locals have a constrained liveness scope by the GC.
// This is needed to avoid keeping previous request references alive for an indeterminate amount
// of time. Update consumer-proguard-rules.pro when modifying this. See also
// https://github.com/google/volley/issues/114
private void processRequest() throws InterruptedException {
long startTimeMs = SystemClock.elapsedRealtime();
// Take a request from the queue.
Request request = mQueue.take();
try {
request.addMarker("network-queue-take");
// If the request was cancelled already, do not perform the
// network request.
if (request.isCanceled()) {
request.finish("network-discard-cancelled");
request.notifyListenerResponseNotUsable();
return;
}
addTrafficStatsTag(request);
// Perform the network request.
NetworkResponse networkResponse = mNetwork.performRequest(request);
request.addMarker("network-http-complete");
// If the server returned 304 AND we delivered a response already,
// we're done -- don't deliver a second identical response.
if (networkResponse.notModified && request.hasHadResponseDelivered()) {
request.finish("not-modified");
request.notifyListenerResponseNotUsable();
return;
}
// Parse the response here on the worker thread.
Response response = request.parseNetworkResponse(networkResponse);
request.addMarker("network-parse-complete");
// Write to cache if applicable.
// TODO: Only update cache metadata instead of entire record for 304s.
if (request.shouldCache() && response.cacheEntry != null) {
mCache.put(request.getCacheKey(), response.cacheEntry);
request.addMarker("network-cache-written");
}
// Post the response back.
request.markDelivered();
mDelivery.postResponse(request, response);
request.notifyListenerResponseReceived(response);
} catch (VolleyError volleyError) {
volleyError.setNetworkTimeMs(SystemClock.elapsedRealtime() - startTimeMs);
parseAndDeliverNetworkError(request, volleyError);
request.notifyListenerResponseNotUsable();
} catch (Exception e) {
VolleyLog.e(e, "Unhandled exception %s", e.toString());
VolleyError volleyError = new VolleyError(e);
volleyError.setNetworkTimeMs(SystemClock.elapsedRealtime() - startTimeMs);
mDelivery.postError(request, volleyError);
request.notifyListenerResponseNotUsable();
}
}
private void parseAndDeliverNetworkError(Request request, VolleyError error) {
error = request.parseNetworkError(error);
mDelivery.postError(request, error);
}
}
线程的run方法是个死循环，会不断的执行processRequest方法
processRequest中阻塞队列会通过take方法从队列头部取出一个request对象，
然后判断队列是否取消了，如果取消了就退出。
如果没取消就执行请求获得NetworkResponse
然后将NetworkResponse解析成Response
如果请求可以被缓存，则将请求结果缓存起来
最后通过ResponseDelivery将结果传递出去。
Request
接下来看看Request的源码
/**
* Base class for all network requests.
*
* @param The type of parsed response this request expects.
*/
public abstract class Request implements Comparable> {
/**
* Default encoding for POST or PUT parameters. See {@link #getParamsEncoding()}.
*/
private static final String DEFAULT_PARAMS_ENCODING = "UTF-8";
/**
* Supported request methods.
*/
public interface Method {
int DEPRECATED_GET_OR_POST = -1;
int GET = 0;
int POST = 1;
int PUT = 2;
int DELETE = 3;
int HEAD = 4;
int OPTIONS = 5;
int TRACE = 6;
int PATCH = 7;
}
/**
* Callback to notify when the network request returns.
*/
/* package */ interface NetworkRequestCompleteListener {
/** Callback when a network response has been received. */
void onResponseReceived(Request request, Response response);
/** Callback when request returns from network without valid response. */
void onNoUsableResponseReceived(Request request);
}
/** An event log tracing the lifetime of this request; for debugging. */
private final MarkerLog mEventLog = MarkerLog.ENABLED ? new MarkerLog() : null;
/**
* Request method of this request. Currently supports GET, POST, PUT, DELETE, HEAD, OPTIONS,
* TRACE, and PATCH.
*/
private final int mMethod;
/** URL of this request. */
private final String mUrl;
/** Default tag for {@link TrafficStats}. */
private final int mDefaultTrafficStatsTag;
/** Lock to guard state which can be mutated after a request is added to the queue. */
private final Object mLock = new Object();
/** Listener interface for errors. */
// @GuardedBy("mLock")
private Response.ErrorListener mErrorListener;
/** Sequence number of this request, used to enforce FIFO ordering. */
private Integer mSequence;
/** The request queue this request is associated with. */
private RequestQueue mRequestQueue;
/** Whether or not responses to this request should be cached. */
private boolean mShouldCache = true;
/** Whether or not this request has been canceled. */
// @GuardedBy("mLock")
private boolean mCanceled = false;
/** Whether or not a response has been delivered for this request yet. */
// @GuardedBy("mLock")
private boolean mResponseDelivered = false;
/** Whether the request should be retried in the event of an HTTP 5xx (server) error. */
private boolean mShouldRetryServerErrors = false;
/** The retry policy for this request. */
private RetryPolicy mRetryPolicy;
/**
* When a request can be retrieved from cache but must be refreshed from
* the network, the cache entry will be stored here so that in the event of
* a "Not Modified" response, we can be sure it hasn't been evicted from cache.
*/
private Cache.Entry mCacheEntry = null;
/** An opaque token tagging this request; used for bulk cancellation. */
private Object mTag;
/** Listener that will be notified when a response has been delivered. */
// @GuardedBy("mLock")
private NetworkRequestCompleteListener mRequestCompleteListener;
/**
* Creates a new request with the given URL and error listener. Note that
* the normal response listener is not provided here as delivery of responses
* is provided by subclasses, who have a better idea of how to deliver an
* already-parsed response.
*
* @deprecated Use {@link #Request(int, String, com.android.volley.Response.ErrorListener)}.
*/
@Deprecated
public Request(String url, Response.ErrorListener listener) {
this(Method.DEPRECATED_GET_OR_POST, url, listener);
}
/**
* Creates a new request with the given method (one of the values from {@link Method}),
* URL, and error listener. Note that the normal response listener is not provided here as
* delivery of responses is provided by subclasses, who have a better idea of how to deliver
* an already-parsed response.
*/
public Request(int method, String url, Response.ErrorListener listener) {
mMethod = method;
mUrl = url;
mErrorListener = listener;
setRetryPolicy(new DefaultRetryPolicy());
mDefaultTrafficStatsTag = findDefaultTrafficStatsTag(url);
}
/**
* Return the method for this request. Can be one of the values in {@link Method}.
*/
public int getMethod() {
return mMethod;
}
/**
* Set a tag on this request. Can be used to cancel all requests with this
* tag by {@link RequestQueue#cancelAll(Object)}.
*
* @return This Request object to allow for chaining.
*/
public Request setTag(Object tag) {
mTag = tag;
return this;
}
/**
* Returns this request's tag.
* @see Request#setTag(Object)
*/
public Object getTag() {
return mTag;
}
/**
* @return this request's {@link com.android.volley.Response.ErrorListener}.
*/
public Response.ErrorListener getErrorListener() {
return mErrorListener;
}
/**
* @return A tag for use with {@link TrafficStats#setThreadStatsTag(int)}
*/
public int getTrafficStatsTag() {
return mDefaultTrafficStatsTag;
}
/**
* @return The hashcode of the URL's host component, or 0 if there is none.
*/
private static int findDefaultTrafficStatsTag(String url) {
if (!TextUtils.isEmpty(url)) {
Uri uri = Uri.parse(url);
if (uri != null) {
String host = uri.getHost();
if (host != null) {
return host.hashCode();
}
}
}
return 0;
}
/**
* Sets the retry policy for this request.
*
* @return This Request object to allow for chaining.
*/
public Request setRetryPolicy(RetryPolicy retryPolicy) {
mRetryPolicy = retryPolicy;
return this;
}
/**
* Adds an event to this request's event log; for debugging.
*/
public void addMarker(String tag) {
if (MarkerLog.ENABLED) {
mEventLog.add(tag, Thread.currentThread().getId());
}
}
/**
* Notifies the request queue that this request has finished (successfully or with error).
*
*
Also dumps all events from this request's event log; for debugging.
*/
void finish(final String tag) {
if (mRequestQueue != null) {
mRequestQueue.finish(this);
}
if (MarkerLog.ENABLED) {
final long threadId = Thread.currentThread().getId();
if (Looper.myLooper() != Looper.getMainLooper()) {
// If we finish marking off of the main thread, we need to
// actually do it on the main thread to ensure correct ordering.
Handler mainThread = new Handler(Looper.getMainLooper());
mainThread.post(new Runnable() {
@Override
public void run() {
mEventLog.add(tag, threadId);
mEventLog.finish(this.toString());
}
});
return;
}
mEventLog.add(tag, threadId);
mEventLog.finish(this.toString());
}
}
/**
* Associates this request with the given queue. The request queue will be notified when this
* request has finished.
*
* @return This Request object to allow for chaining.
*/
public Request setRequestQueue(RequestQueue requestQueue) {
mRequestQueue = requestQueue;
return this;
}
/**
* Sets the sequence number of this request. Used by {@link RequestQueue}.
*
* @return This Request object to allow for chaining.
*/
public final Request setSequence(int sequence) {
mSequence = sequence;
return this;
}
/**
* Returns the sequence number of this request.
*/
public final int getSequence() {
if (mSequence == null) {
throw new IllegalStateException("getSequence called before setSequence");
}
return mSequence;
}
/**
* Returns the URL of this request.
*/
public String getUrl() {
return mUrl;
}
/**
* Returns the cache key for this request. By default, this is the URL.
*/
public String getCacheKey() {
return getUrl();
}
/**
* Annotates this request with an entry retrieved for it from cache.
* Used for cache coherency support.
*
* @return This Request object to allow for chaining.
*/
public Request setCacheEntry(Cache.Entry entry) {
mCacheEntry = entry;
return this;
}
/**
* Returns the annotated cache entry, or null if there isn't one.
*/
public Cache.Entry getCacheEntry() {
return mCacheEntry;
}
/**
* Mark this request as canceled.
*
*
No callback will be delivered as long as either:
*
*
- This method is called on the same thread as the {@link ResponseDelivery} is running
* on. By default, this is the main thread.
*
- The request subclass being used overrides cancel() and ensures that it does not
* invoke the listener in {@link #deliverResponse} after cancel() has been called in a
* thread-safe manner.
*
*
*
There are no guarantees if both of these conditions aren't met.
*/
// @CallSuper
public void cancel() {
synchronized (mLock) {
mCanceled = true;
mErrorListener = null;
}
}
/**
* Returns true if this request has been canceled.
*/
public boolean isCanceled() {
synchronized (mLock) {
return mCanceled;
}
}
/**
* Returns a list of extra HTTP headers to go along with this request. Can
* throw {@link AuthFailureError} as authentication may be required to
* provide these values.
* @throws AuthFailureError In the event of auth failure
*/
public Map getHeaders() throws AuthFailureError {
return Collections.emptyMap();
}
/**
* Returns a Map of POST parameters to be used for this request, or null if
* a simple GET should be used. Can throw {@link AuthFailureError} as
* authentication may be required to provide these values.
*
*
Note that only one of getPostParams() and getPostBody() can return a non-null
* value.
* @throws AuthFailureError In the event of auth failure
*
* @deprecated Use {@link #getParams()} instead.
*/
@Deprecated
protected Map getPostParams() throws AuthFailureError {
return getParams();
}
/**
* Returns which encoding should be used when converting POST parameters returned by
* {@link #getPostParams()} into a raw POST body.
*
*
This controls both encodings:
*
*
- The string encoding used when converting parameter names and values into bytes prior
* to URL encoding them.
*
- The string encoding used when converting the URL encoded parameters into a raw
* byte array.
*
*
* @deprecated Use {@link #getParamsEncoding()} instead.
*/
@Deprecated
protected String getPostParamsEncoding() {
return getParamsEncoding();
}
/**
* @deprecated Use {@link #getBodyContentType()} instead.
*/
@Deprecated
public String getPostBodyContentType() {
return getBodyContentType();
}
/**
* Returns the raw POST body to be sent.
*
* @throws AuthFailureError In the event of auth failure
*
* @deprecated Use {@link #getBody()} instead.
*/
@Deprecated
public byte[] getPostBody() throws AuthFailureError {
// Note: For compatibility with legacy clients of volley, this implementation must remain
// here instead of simply calling the getBody() function because this function must
// call getPostParams() and getPostParamsEncoding() since legacy clients would have
// overridden these two member functions for POST requests.
Map postParams = getPostParams();
if (postParams != null && postParams.size() > 0) {
return encodeParameters(postParams, getPostParamsEncoding());
}
return null;
}
/**
* Returns a Map of parameters to be used for a POST or PUT request. Can throw
* {@link AuthFailureError} as authentication may be required to provide these values.
*
*
Note that you can directly override {@link #getBody()} for custom data.
*
* @throws AuthFailureError in the event of auth failure
*/
protected Map getParams() throws AuthFailureError {
return null;
}
/**
* Returns which encoding should be used when converting POST or PUT parameters returned by
* {@link #getParams()} into a raw POST or PUT body.
*
*
This controls both encodings:
*
*
- The string encoding used when converting parameter names and values into bytes prior
* to URL encoding them.
*
- The string encoding used when converting the URL encoded parameters into a raw
* byte array.
*
*/
protected String getParamsEncoding() {
return DEFAULT_PARAMS_ENCODING;
}
/**
* Returns the content type of the POST or PUT body.
*/
public String getBodyContentType() {
return "application/x-www-form-urlencoded; charset=" + getParamsEncoding();
}
/**
* Returns the raw POST or PUT body to be sent.
*
*
By default, the body consists of the request parameters in
* application/x-www-form-urlencoded format. When overriding this method, consider overriding
* {@link #getBodyContentType()} as well to match the new body format.
*
* @throws AuthFailureError in the event of auth failure
*/
public byte[] getBody() throws AuthFailureError {
Map params = getParams();
if (params != null && params.size() > 0) {
return encodeParameters(params, getParamsEncoding());
}
return null;
}
/**
* Converts `params` into an application/x-www-form-urlencoded encoded string.
*/
private byte[] encodeParameters(Map params, String paramsEncoding) {
StringBuilder encodedParams = new StringBuilder();
try {
for (Map.Entry entry : params.entrySet()) {
encodedParams.append(URLEncoder.encode(entry.getKey(), paramsEncoding));
encodedParams.append('=');
encodedParams.append(URLEncoder.encode(entry.getValue(), paramsEncoding));
encodedParams.append('&');
}
return encodedParams.toString().getBytes(paramsEncoding);
} catch (UnsupportedEncodingException uee) {
throw new RuntimeException("Encoding not supported: " + paramsEncoding, uee);
}
}
/**
* Set whether or not responses to this request should be cached.
*
* @return This Request object to allow for chaining.
*/
public final Request setShouldCache(boolean shouldCache) {
mShouldCache = shouldCache;
return this;
}
/**
* Returns true if responses to this request should be cached.
*/
public final boolean shouldCache() {
return mShouldCache;
}
/**
* Sets whether or not the request should be retried in the event of an HTTP 5xx (server) error.
*
* @return This Request object to allow for chaining.
*/
public final Request setShouldRetryServerErrors(boolean shouldRetryServerErrors) {
mShouldRetryServerErrors = shouldRetryServerErrors;
return this;
}
/**
* Returns true if this request should be retried in the event of an HTTP 5xx (server) error.
*/
public final boolean shouldRetryServerErrors() {
return mShouldRetryServerErrors;
}
/**
* Priority values. Requests will be processed from higher priorities to
* lower priorities, in FIFO order.
*/
public enum Priority {
LOW,
NORMAL,
HIGH,
IMMEDIATE
}
/**
* Returns the {@link Priority} of this request; {@link Priority#NORMAL} by default.
*/
public Priority getPriority() {
return Priority.NORMAL;
}
/**
* Returns the socket timeout in milliseconds per retry attempt. (This value can be changed
* per retry attempt if a backoff is specified via backoffTimeout()). If there are no retry
* attempts remaining, this will cause delivery of a {@link TimeoutError} error.
*/
public final int getTimeoutMs() {
return mRetryPolicy.getCurrentTimeout();
}
/**
* Returns the retry policy that should be used for this request.
*/
public RetryPolicy getRetryPolicy() {
return mRetryPolicy;
}
/**
* Mark this request as having a response delivered on it. This can be used
* later in the request's lifetime for suppressing identical responses.
*/
public void markDelivered() {
synchronized (mLock) {
mResponseDelivered = true;
}
}
/**
* Returns true if this request has had a response delivered for it.
*/
public boolean hasHadResponseDelivered() {
synchronized (mLock) {
return mResponseDelivered;
}
}
/**
* Subclasses must implement this to parse the raw network response
* and return an appropriate response type. This method will be
* called from a worker thread. The response will not be delivered
* if you return null.
* @param response Response from the network
* @return The parsed response, or null in the case of an error
*/
abstract protected Response parseNetworkResponse(NetworkResponse response);
/**
* Subclasses can override this method to parse 'networkError' and return a more specific error.
*
*
The default implementation just returns the passed 'networkError'.
*
* @param volleyError the error retrieved from the network
* @return an NetworkError augmented with additional information
*/
protected VolleyError parseNetworkError(VolleyError volleyError) {
return volleyError;
}
/**
* Subclasses must implement this to perform delivery of the parsed
* response to their listeners. The given response is guaranteed to
* be non-null; responses that fail to parse are not delivered.
* @param response The parsed response returned by
* {@link #parseNetworkResponse(NetworkResponse)}
*/
abstract protected void deliverResponse(T response);
/**
* Delivers error message to the ErrorListener that the Request was
* initialized with.
*
* @param error Error details
*/
public void deliverError(VolleyError error) {
Response.ErrorListener listener;
synchronized (mLock) {
listener = mErrorListener;
}
if (listener != null) {
listener.onErrorResponse(error);
}
}
/**
* {@link NetworkRequestCompleteListener} that will receive callbacks when the request
* returns from the network.
*/
/* package */ void setNetworkRequestCompleteListener(
NetworkRequestCompleteListener requestCompleteListener) {
synchronized (mLock) {
mRequestCompleteListener = requestCompleteListener;
}
}
/**
* Notify NetworkRequestCompleteListener that a valid response has been received
* which can be used for other, waiting requests.
* @param response received from the network
*/
/* package */ void notifyListenerResponseReceived(Response response) {
NetworkRequestCompleteListener listener;
synchronized (mLock) {
listener = mRequestCompleteListener;
}
if (listener != null) {
listener.onResponseReceived(this, response);
}
}
/**
* Notify NetworkRequestCompleteListener that the network request did not result in
* a response which can be used for other, waiting requests.
*/
/* package */ void notifyListenerResponseNotUsable() {
NetworkRequestCompleteListener listener;
synchronized (mLock) {
listener = mRequestCompleteListener;
}
if (listener != null) {
listener.onNoUsableResponseReceived(this);
}
}
/**
* Our comparator sorts from high to low priority, and secondarily by
* sequence number to provide FIFO ordering.
*/
@Override
public int compareTo(Request other) {
Priority left = this.getPriority();
Priority right = other.getPriority();
// High-priority requests are "lesser" so they are sorted to the front.
// Equal priorities are sorted by sequence number to provide FIFO ordering.
return left == right ?
this.mSequence - other.mSequence :
right.ordinal() - left.ordinal();
}
@Override
public String toString() {
String trafficStatsTag = "0x" + Integer.toHexString(getTrafficStatsTag());
return (mCanceled ? "[X] " : "[ ] ") + getUrl() + " " + trafficStatsTag + " "
+ getPriority() + " " + mSequence;
}
}
我们所熟知的StringRequest,JsonArrayRequest等都是继承于Request这个类。
主要实现其中的两个方法
/**
* Subclasses must implement this to parse the raw network response
* and return an appropriate response type. This method will be
* called from a worker thread. The response will not be delivered
* if you return null.
* @param response Response from the network
* @return The parsed response, or null in the case of an error
*/
abstract protected Response parseNetworkResponse(NetworkResponse response);
这个方法用于把NetworkResponse转成response对象
/**
* Subclasses must implement this to perform delivery of the parsed
* response to their listeners. The given response is guaranteed to
* be non-null; responses that fail to parse are not delivered.
* @param response The parsed response returned by
* {@link #parseNetworkResponse(NetworkResponse)}
*/
abstract protected void deliverResponse(T response);
这个方法用于分发response
Network
/**
* An interface for performing requests.
*/
public interface Network {
/**
* Performs the specified request.
* @param request Request to process
* @return A {@link NetworkResponse} with data and caching metadata; will never be null
* @throws VolleyError on errors
*/
NetworkResponse performRequest(Request request) throws VolleyError;
}
这个接口用于执行网络请求并返回一个NetworkResponse
BasicNetwork
/**
* A network performing Volley requests over an {@link HttpStack}.
*/
public class BasicNetwork implements Network {
protected static final boolean DEBUG = VolleyLog.DEBUG;
private static final int SLOW_REQUEST_THRESHOLD_MS = 3000;
private static final int DEFAULT_POOL_SIZE = 4096;
/**
* @deprecated Should never have been exposed in the API. This field may be removed in a future
* release of Volley.
*/
@Deprecated
protected final HttpStack mHttpStack;
private final BaseHttpStack mBaseHttpStack;
protected final ByteArrayPool mPool;
/**
* @param httpStack HTTP stack to be used
* @deprecated use {@link #BasicNetwork(BaseHttpStack)} instead to avoid depending on Apache
* HTTP. This method may be removed in a future release of Volley.
*/
@Deprecated
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
* @deprecated use {@link #BasicNetwork(BaseHttpStack, ByteArrayPool)} instead to avoid
* depending on Apache HTTP. This method may be removed in a future release of
* Volley.
*/
@Deprecated
public BasicNetwork(HttpStack httpStack, ByteArrayPool pool) {
mHttpStack = httpStack;
mBaseHttpStack = new AdaptedHttpStack(httpStack);
mPool = pool;
}
/**
* @param httpStack HTTP stack to be used
*/
public BasicNetwork(BaseHttpStack 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(BaseHttpStack httpStack, ByteArrayPool pool) {
mBaseHttpStack = httpStack;
// Populate mHttpStack for backwards compatibility, since it is a protected field. However,
// we won't use it directly here, so clients which don't access it directly won't need to
// depend on Apache HTTP.
mHttpStack = httpStack;
mPool = pool;
}
@Override
public NetworkResponse performRequest(Request request) throws VolleyError {
long requestStart = SystemClock.elapsedRealtime();
while (true) {
HttpResponse httpResponse = null;
byte[] responseContents = null;
List responseHeaders = Collections.emptyList();
try {
// Gather headers.
Map additionalRequestHeaders =
getCacheHeaders(request.getCacheEntry());
httpResponse = mBaseHttpStack.executeRequest(request, additionalRequestHeaders);
int statusCode = httpResponse.getStatusCode();
responseHeaders = httpResponse.getHeaders();
// Handle cache validation.
if (statusCode == HttpURLConnection.HTTP_NOT_MODIFIED) {
Entry entry = request.getCacheEntry();
if (entry == null) {
return new NetworkResponse(HttpURLConnection.HTTP_NOT_MODIFIED, null, true,
SystemClock.elapsedRealtime() - requestStart, responseHeaders);
}
// Combine cached and response headers so the response will be complete.
List combinedHeaders = combineHeaders(responseHeaders, entry);
return new NetworkResponse(HttpURLConnection.HTTP_NOT_MODIFIED, entry.data,
true, SystemClock.elapsedRealtime() - requestStart, combinedHeaders);
}
// Some responses such as 204s do not have content. We must check.
InputStream inputStream = httpResponse.getContent();
if (inputStream != null) {
responseContents =
inputStreamToBytes(inputStream, httpResponse.getContentLength());
} 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, statusCode);
if (statusCode < 200 || statusCode > 299) {
throw new IOException();
}
return new NetworkResponse(statusCode, responseContents, false,
SystemClock.elapsedRealtime() - requestStart, responseHeaders);
} catch (SocketTimeoutException e) {
attemptRetryOnException("socket", request, new TimeoutError());
} catch (MalformedURLException e) {
throw new RuntimeException("Bad URL " + request.getUrl(), e);
} catch (IOException e) {
int statusCode;
if (httpResponse != null) {
statusCode = httpResponse.getStatusCode();
} else {
throw new NoConnectionError(e);
}
VolleyLog.e("Unexpected response code %d for %s", statusCode, request.getUrl());
NetworkResponse networkResponse;
if (responseContents != null) {
networkResponse = new NetworkResponse(statusCode, responseContents, false,
SystemClock.elapsedRealtime() - requestStart, responseHeaders);
if (statusCode == HttpURLConnection.HTTP_UNAUTHORIZED ||
statusCode == HttpURLConnection.HTTP_FORBIDDEN) {
attemptRetryOnException("auth",
request, new AuthFailureError(networkResponse));
} else if (statusCode >= 400 && statusCode <= 499) {
// Don't retry other client errors.
throw new ClientError(networkResponse);
} else if (statusCode >= 500 && statusCode <= 599) {
if (request.shouldRetryServerErrors()) {
attemptRetryOnException("server",
request, new ServerError(networkResponse));
} else {
throw new ServerError(networkResponse);
}
} else {
// 3xx? No reason to retry.
throw new ServerError(networkResponse);
}
} else {
attemptRetryOnException("network", request, new NetworkError());
}
}
}
}
/**
* Logs requests that took over SLOW_REQUEST_THRESHOLD_MS to complete.
*/
private void logSlowRequests(long requestLifetime, Request request,
byte[] responseContents, int statusCode) {
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",
statusCode, 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 static 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));
}
private Map getCacheHeaders(Cache.Entry entry) {
// If there's no cache entry, we're done.
if (entry == null) {
return Collections.emptyMap();
}
Map headers = new HashMap<>();
if (entry.etag != null) {
headers.put("If-None-Match", entry.etag);
}
if (entry.lastModified > 0) {
headers.put("If-Modified-Since",
HttpHeaderParser.formatEpochAsRfc1123(entry.lastModified));
}
return headers;
}
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 an InputStream into a byte[]. */
private byte[] inputStreamToBytes(InputStream in, int contentLength)
throws IOException, ServerError {
PoolingByteArrayOutputStream bytes =
new PoolingByteArrayOutputStream(mPool, contentLength);
byte[] buffer = null;
try {
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".
if (in != null) {
in.close();
}
} catch (IOException e) {
// This can happen if there was an exception above that left the stream in
// an invalid state.
VolleyLog.v("Error occurred when closing InputStream");
}
mPool.returnBuf(buffer);
bytes.close();
}
}
/**
* Converts Headers[] to Map<String, String>.
*
* @deprecated Should never have been exposed in the API. This method may be removed in a future
* release of Volley.
*/
@Deprecated
protected static Map convertHeaders(Header[] headers) {
Map result = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
for (int i = 0; i < headers.length; i++) {
result.put(headers[i].getName(), headers[i].getValue());
}
return result;
}
/**
* Combine cache headers with network response headers for an HTTP 304 response.
*
*
An 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. See also:
* http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.5
*
* @param responseHeaders Headers from the network response.
* @param entry The cached response.
* @return The combined list of headers.
*/
private static List combineHeaders(List responseHeaders, Entry entry) {
// First, create a case-insensitive set of header names from the network
// response.
Set headerNamesFromNetworkResponse =
new TreeSet<>(String.CASE_INSENSITIVE_ORDER);
if (!responseHeaders.isEmpty()) {
for (Header header : responseHeaders) {
headerNamesFromNetworkResponse.add(header.getName());
}
}
// Second, add headers from the cache entry to the network response as long as
// they didn't appear in the network response, which should take precedence.
List combinedHeaders = new ArrayList<>(responseHeaders);
if (entry.allResponseHeaders != null) {
if (!entry.allResponseHeaders.isEmpty()) {
for (Header header : entry.allResponseHeaders) {
if (!headerNamesFromNetworkResponse.contains(header.getName())) {
combinedHeaders.add(header);
}
}
}
} else {
// Legacy caches only have entry.responseHeaders.
if (!entry.responseHeaders.isEmpty()) {
for (Map.Entry header : entry.responseHeaders.entrySet()) {
if (!headerNamesFromNetworkResponse.contains(header.getKey())) {
combinedHeaders.add(new Header(header.getKey(), header.getValue()));
}
}
}
}
return combinedHeaders;
}
}
BasicNetwork是Network的实现类
performRequest方法中
先获取缓存的请求头，然后由mBaseHttpStack带上请求头去执行请求
// Gather headers.
Map additionalRequestHeaders =
getCacheHeaders(request.getCacheEntry());
httpResponse = mBaseHttpStack.executeRequest(request, additionalRequestHeaders);
然后对304和204状态码进行处理
当请求发生异常后会调用attemptRetryOnException执行重试
重试策略参考RetryPolicy
我们在创建Request时可以自定义重试策略
/**
* Sets the retry policy for this request.
*
* @return This Request object to allow for chaining.
*/
public Request setRetryPolicy(RetryPolicy retryPolicy) {
mRetryPolicy = retryPolicy;
return this;
}
ResponseDelivery
public interface ResponseDelivery {
/**
* Parses a response from the network or cache and delivers it.
*/
void postResponse(Request request, Response response);
/**
* Parses a response from the network or cache and delivers it. The provided
* Runnable will be executed after delivery.
*/
void postResponse(Request request, Response response, Runnable runnable);
/**
* Posts an error for the given request.
*/
void postError(Request request, VolleyError error);
}
这个接口是用于分发response 即实现请求回调
实现类为ExecutorDelivery
ExecutorDelivery
/**
* Delivers responses and errors.
*/
public class ExecutorDelivery implements ResponseDelivery {
/** Used for posting responses, typically to the main thread. */
private final Executor mResponsePoster;
/**
* Creates a new response delivery interface.
* @param handler {@link Handler} to post responses on
*/
public ExecutorDelivery(final Handler handler) {
// Make an Executor that just wraps the handler.
mResponsePoster = new Executor() {
@Override
public void execute(Runnable command) {
handler.post(command);
}
};
}
/**
* Creates a new response delivery interface, mockable version
* for testing.
* @param executor For running delivery tasks
*/
public ExecutorDelivery(Executor executor) {
mResponsePoster = executor;
}
@Override
public void postResponse(Request request, Response response) {
postResponse(request, response, null);
}
@Override
public void postResponse(Request request, Response response, Runnable runnable) {
request.markDelivered();
request.addMarker("post-response");
mResponsePoster.execute(new ResponseDeliveryRunnable(request, response, runnable));
}
@Override
public void postError(Request request, VolleyError error) {
request.addMarker("post-error");
Response response = Response.error(error);
mResponsePoster.execute(new ResponseDeliveryRunnable(request, response, null));
}
/**
* A Runnable used for delivering network responses to a listener on the
* main thread.
*/
@SuppressWarnings("rawtypes")
private class ResponseDeliveryRunnable implements Runnable {
private final Request mRequest;
private final Response mResponse;
private final Runnable mRunnable;
public ResponseDeliveryRunnable(Request request, Response response, Runnable runnable) {
mRequest = request;
mResponse = response;
mRunnable = runnable;
}
@SuppressWarnings("unchecked")
@Override
public void run() {
// NOTE: If cancel() is called off the thread that we're currently running in (by
// default, the main thread), we cannot guarantee that deliverResponse()/deliverError()
// won't be called, since it may be canceled after we check isCanceled() but before we
// deliver the response. Apps concerned about this guarantee must either call cancel()
// from the same thread or implement their own guarantee about not invoking their
// listener after cancel() has been called.
// If this request has canceled, finish it and don't deliver.
if (mRequest.isCanceled()) {
mRequest.finish("canceled-at-delivery");
return;
}
// Deliver a normal response or error, depending.
if (mResponse.isSuccess()) {
mRequest.deliverResponse(mResponse.result);
} else {
mRequest.deliverError(mResponse.error);
}
// If this is an intermediate response, add a marker, otherwise we're done
// and the request can be finished.
if (mResponse.intermediate) {
mRequest.addMarker("intermediate-response");
} else {
mRequest.finish("done");
}
// If we have been provided a post-delivery runnable, run it.
if (mRunnable != null) {
mRunnable.run();
}
}
}
}
在启动RequestQueue的时候被传到Dispatcher中
// Create the cache dispatcher and start it.
mCacheDispatcher = new CacheDispatcher(mCacheQueue, mNetworkQueue, mCache, mDelivery);
mCacheDispatcher.start();
// Create network dispatchers (and corresponding threads) up to the pool size.
for (int i = 0; i < mDispatchers.length; i++) {
NetworkDispatcher networkDispatcher = new NetworkDispatcher(mNetworkQueue, mNetwork,
mCache, mDelivery);
mDispatchers[i] = networkDispatcher;
networkDispatcher.start();
}
而ExecutorDelivery在构造的时候会传入一个主线程looper的handler对象
/**
* Creates the worker pool. Processing will not begin until {@link #start()} is called.
*
* @param cache A Cache to use for persisting responses to disk
* @param network A Network interface for performing HTTP requests
* @param threadPoolSize Number of network dispatcher threads to create
*/
public RequestQueue(Cache cache, Network network, int threadPoolSize) {
this(cache, network, threadPoolSize,
new ExecutorDelivery(new Handler(Looper.getMainLooper())));
}
ExecutorDelivery会对handler进行一个封装
/**
* Creates a new response delivery interface.
* @param handler {@link Handler} to post responses on
*/
public ExecutorDelivery(final Handler handler) {
// Make an Executor that just wraps the handler.
mResponsePoster = new Executor() {
@Override
public void execute(Runnable command) {
handler.post(command);
}
};
}
在Dispatcher中执行完请求后就调用ExecutorDelivery的postResponse方法
然后在ResponseDeliveryRunnable中对response进行判断，如果成功就执行request的deliverResponse 如果失败就执行request的deliverError
// Post the response back.
request.markDelivered();
mDelivery.postResponse(request, response);
request.notifyListenerResponseReceived(response);
// Deliver a normal response or error, depending.
if (mResponse.isSuccess()) {
mRequest.deliverResponse(mResponse.result);
} else {
mRequest.deliverError(mResponse.error);
}
缓存和图片加载
后续在写
附上Okhttp的实现
public class OkHttpStack extends BaseHttpStack {
private final OkHttpClient okHttpClient;
/**
* Create a OkHttpStack with default OkHttpClient.
*/
public OkHttpStack() {
this(new OkHttpClient());
}
/**
* Create a OkHttpStack with a custom OkHttpClient
*
* @param okHttpClient Custom OkHttpClient, NonNull
*/
public OkHttpStack(OkHttpClient okHttpClient) {
this.okHttpClient = okHttpClient;
}
@Override
public HttpResponse executeRequest(Request request, Map additionalHeaders) throws IOException, AuthFailureError {
int timeoutMs = request.getTimeoutMs();
okHttpClient.newBuilder().readTimeout(timeoutMs, TimeUnit.MILLISECONDS)
.connectTimeout(timeoutMs, TimeUnit.MILLISECONDS)
.writeTimeout(timeoutMs, TimeUnit.MILLISECONDS)
.cookieJar(new CookieJar() {
@Override
public void saveFromResponse(@NonNull HttpUrl url, @NonNull List cookies) {
}
@Override
public List loadForRequest(@NonNull HttpUrl url) {
return null;
}
})
.build();
okhttp3.Request.Builder builder = new okhttp3.Request.Builder();
Map headers = request.getHeaders();
for (final String name : headers.keySet()) {
builder.addHeader(name, headers.get(name));
}
for (final String name : additionalHeaders.keySet()) {
builder.addHeader(name, additionalHeaders.get(name));
}
setConnectionParametersForRequest(builder, request);
String url = request.getUrl();
okhttp3.Request okhttpRequest = builder.url(url).build();
Response okHttpResponse = okHttpClient.newCall(okhttpRequest).execute();
int statusCode = okHttpResponse.code();
Headers responseHeaders = okHttpResponse.headers();
List headerList = new ArrayList<>();
for (int i = 0, len = responseHeaders.size(); i < len; i++) {
final String name = responseHeaders.name(i), value = responseHeaders.value(i);
if (name != null) {
Header header = new Header(name, value);
headerList.add(header);
}
}
ResponseBody body = okHttpResponse.body();
if (body != null) {
long contentLength = body.contentLength();
InputStream inputStream = body.byteStream();
return new HttpResponse(statusCode, headerList, (int) contentLength, inputStream);
}
return null;
}
private static void setConnectionParametersForRequest(okhttp3.Request.Builder builder, Request request)
throws IOException, AuthFailureError {
switch (request.getMethod()) {
case Request.Method.DEPRECATED_GET_OR_POST:
byte[] postBody = request.getPostBody();
if (postBody != null) {
builder.post(RequestBody.create
(MediaType.parse(request.getPostBodyContentType()), postBody));
}
break;
case Request.Method.GET:
builder.get();
break;
case Request.Method.DELETE:
builder.delete();
break;
case Request.Method.POST:
builder.post(createRequestBody(request));
break;
case Request.Method.PUT:
builder.put(createRequestBody(request));
break;
case Request.Method.HEAD:
builder.head();
break;
case Request.Method.OPTIONS:
builder.method("OPTIONS", null);
break;
case Request.Method.TRACE:
builder.method("TRACE", null);
break;
case Request.Method.PATCH:
builder.patch(createRequestBody(request));
break;
default:
throw new IllegalStateException("Unknown method type.");
}
}
private static RequestBody createRequestBody(Request request) throws AuthFailureError {
final byte[] body = request.getBody();
if (body == null) return null;
return RequestBody.create(MediaType.parse(request.getBodyContentType()), body);
}
}
UML
了解一下
