上一篇文章从功能和用法上对AsyncHttpClient做了个大致介绍,今天我们和以往一样,从内部实现、原理的角度带领大家看看
其工作机制,以便加深理解。写程序越多,我发现每接触一个新东西,都会有强烈的想知道它内部怎么工作的冲动。可能只有知道了
内部原理能更容易写出高质量的代码吧。
我大概浏览了下其代码,关键部分可以分为这4个模块:
1. AsyncHttpClient自己一个模块;
2. AsyncHttpRequest和RequestHandler一个模块;
3. AsyncHttpResponseHandler及其各种特定子类一个模块;
4. RetryHandler,自动重试机制。
我们可以很清楚的看出门道来,大体是按照client、request、response,这样的方式组织的。接下来我们的代码分析也就按照这个顺序进行。
先来说AsyncHttpClient,来看其关键字段和ctor,代码如下:
- public static final String LOG_TAG = "AsyncHttpClient";
- public static final String HEADER_CONTENT_TYPE = "Content-Type";
- public static final String HEADER_CONTENT_RANGE = "Content-Range";
- public static final String HEADER_CONTENT_ENCODING = "Content-Encoding";
- public static final String HEADER_CONTENT_DISPOSITION = "Content-Disposition";
- public static final String HEADER_ACCEPT_ENCODING = "Accept-Encoding";
- public static final String ENCODING_GZIP = "gzip";
- public static final int DEFAULT_MAX_CONNECTIONS = 10;
- public static final int DEFAULT_SOCKET_TIMEOUT = 10 * 1000;
- public static final int DEFAULT_MAX_RETRIES = 5;
- public static final int DEFAULT_RETRY_SLEEP_TIME_MILLIS = 1500;
- public static final int DEFAULT_SOCKET_BUFFER_SIZE = 8192;
- private int maxConnections = DEFAULT_MAX_CONNECTIONS;
- private int connectTimeout = DEFAULT_SOCKET_TIMEOUT;
- private int responseTimeout = DEFAULT_SOCKET_TIMEOUT; // 各种参数设置
- private final DefaultHttpClient httpClient; // 包装的Apache DefaultHttpClient
- private final HttpContext httpContext;
- private ExecutorService threadPool; // 执行网络请求的线程池
- private final Map<Context, List<RequestHandle>> requestMap; // 与Android Context对应的请求map
- private final Map<String, String> clientHeaderMap; // 客户端的请求header map
- private boolean isUrlEncodingEnabled = true; // 允许url encoding
接下来看看各种ctor,如下:
- /**
- * Creates a new AsyncHttpClient with default constructor arguments values
- */
- public AsyncHttpClient() { // 一般客户端代码中都直接调用这个版本的ctor
- this(false, 80, 443);
- }
- /**
- * Creates a new AsyncHttpClient.
- *
- * @param httpPort non-standard HTTP-only port
- */
- public AsyncHttpClient(int httpPort) {
- this(false, httpPort, 443);
- }
- /**
- * Creates a new AsyncHttpClient.
- *
- * @param httpPort non-standard HTTP-only port
- * @param httpsPort non-standard HTTPS-only port
- */
- public AsyncHttpClient(int httpPort, int httpsPort) {
- this(false, httpPort, httpsPort);
- }
- /**
- * Creates new AsyncHttpClient using given params
- *
- * @param fixNoHttpResponseException Whether to fix or not issue, by omitting SSL verification
- * @param httpPort HTTP port to be used, must be greater than 0
- * @param httpsPort HTTPS port to be used, must be greater than 0
- */
- public AsyncHttpClient(boolean fixNoHttpResponseException, int httpPort, int httpsPort) {
- this(getDefaultSchemeRegistry(fixNoHttpResponseException, httpPort, httpsPort));
- }
- /**
- * Returns default instance of SchemeRegistry
- *
- * @param fixNoHttpResponseException Whether to fix or not issue, by omitting SSL verification
- * @param httpPort HTTP port to be used, must be greater than 0
- * @param httpsPort HTTPS port to be used, must be greater than 0
- */
- private static SchemeRegistry getDefaultSchemeRegistry(boolean fixNoHttpResponseException, int httpPort, int httpsPort) {
- if (fixNoHttpResponseException) { // 如果你请求的url是https的,并且遇到了SSL验证之类的错误,那么你应该将此值设为true试试
- Log.d(LOG_TAG, "Beware! Using the fix is insecure, as it doesn't verify SSL certificates.");
- }
- if (httpPort < 1) {
- httpPort = 80;
- Log.d(LOG_TAG, "Invalid HTTP port number specified, defaulting to 80");
- }
- if (httpsPort < 1) {
- httpsPort = 443;
- Log.d(LOG_TAG, "Invalid HTTPS port number specified, defaulting to 443");
- }
- // Fix to SSL flaw in API < ICS
- // See https://code.google.com/p/android/issues/detail?id=13117
- SSLSocketFactory sslSocketFactory;
- if (fixNoHttpResponseException) { // 感兴趣的同学可自行看看MySSLSocketFactory的实现,基本上是省略了SSL验证环节
- sslSocketFactory = MySSLSocketFactory.getFixedSocketFactory();
- } else {
- sslSocketFactory = SSLSocketFactory.getSocketFactory();
- }
- SchemeRegistry schemeRegistry = new SchemeRegistry();
- schemeRegistry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), httpPort));
- schemeRegistry.register(new Scheme("https", sslSocketFactory, httpsPort));
- return schemeRegistry;
- }
- /**
- * Creates a new AsyncHttpClient.
- *
- * @param schemeRegistry SchemeRegistry to be used
- */
- public AsyncHttpClient(SchemeRegistry schemeRegistry) { // 最终调到的是这个版本。。。
- BasicHttpParams httpParams = new BasicHttpParams();
- // 接下来是设置各种参数。。。
- ConnManagerParams.setTimeout(httpParams, connectTimeout);
- ConnManagerParams.setMaxConnectionsPerRoute(httpParams, new ConnPerRouteBean(maxConnections));
- ConnManagerParams.setMaxTotalConnections(httpParams, DEFAULT_MAX_CONNECTIONS);
- HttpConnectionParams.setSoTimeout(httpParams, responseTimeout);
- HttpConnectionParams.setConnectionTimeout(httpParams, connectTimeout);
- HttpConnectionParams.setTcpNoDelay(httpParams, true);
- HttpConnectionParams.setSocketBufferSize(httpParams, DEFAULT_SOCKET_BUFFER_SIZE);
- HttpProtocolParams.setVersion(httpParams, HttpVersion.HTTP_1_1);
- ThreadSafeClientConnManager cm = new ThreadSafeClientConnManager(httpParams, schemeRegistry);
- // 初始化关键字段
- threadPool = getDefaultThreadPool();
- requestMap = Collections.synchronizedMap(new WeakHashMap<Context, List<RequestHandle>>());
- clientHeaderMap = new HashMap<String, String>();
- httpContext = new SyncBasicHttpContext(new BasicHttpContext());
- httpClient = new DefaultHttpClient(cm, httpParams);
- httpClient.addRequestInterceptor(new HttpRequestInterceptor() {
- @Override
- public void process(HttpRequest request, HttpContext context) {
- if (!request.containsHeader(HEADER_ACCEPT_ENCODING)) {
- request.addHeader(HEADER_ACCEPT_ENCODING, ENCODING_GZIP);
- }
- for (String header : clientHeaderMap.keySet()) {
- if (request.containsHeader(header)) {
- Header overwritten = request.getFirstHeader(header);
- Log.d(LOG_TAG,
- String.format("Headers were overwritten! (%s | %s) overwrites (%s | %s)",
- header, clientHeaderMap.get(header),
- overwritten.getName(), overwritten.getValue())
- );
- //remove the overwritten header
- request.removeHeader(overwritten);
- }
- request.addHeader(header, clientHeaderMap.get(header));
- }
- }
- });
- httpClient.addResponseInterceptor(new HttpResponseInterceptor() {
- @Override
- public void process(HttpResponse response, HttpContext context) {
- final HttpEntity entity = response.getEntity();
- if (entity == null) {
- return;
- }
- final Header encoding = entity.getContentEncoding();
- if (encoding != null) {
- for (HeaderElement element : encoding.getElements()) {
- if (element.getName().equalsIgnoreCase(ENCODING_GZIP)) {
- response.setEntity(new InflatingEntity(entity));
- break;
- }
- }
- }
- }
- });
- httpClient.addRequestInterceptor(new HttpRequestInterceptor() {
- @Override
- public void process(final HttpRequest request, final HttpContext context) throws HttpException, IOException {
- AuthState authState = (AuthState) context.getAttribute(ClientContext.TARGET_AUTH_STATE);
- CredentialsProvider credsProvider = (CredentialsProvider) context.getAttribute(
- ClientContext.CREDS_PROVIDER);
- HttpHost targetHost = (HttpHost) context.getAttribute(ExecutionContext.HTTP_TARGET_HOST);
- if (authState.getAuthScheme() == null) {
- AuthScope authScope = new AuthScope(targetHost.getHostName(), targetHost.getPort());
- Credentials creds = credsProvider.getCredentials(authScope);
- if (creds != null) {
- authState.setAuthScheme(new BasicScheme());
- authState.setCredentials(creds);
- }
- }
- }
- }, 0);
- // 设置重试Handler,会在合适的情况下自动重试
- httpClient.setHttpRequestRetryHandler(new RetryHandler(DEFAULT_MAX_RETRIES, DEFAULT_RETRY_SLEEP_TIME_MILLIS));
- }
- 接下来重要的就是各种HTTP head、get、post、delete方法,它们最终调用的都是sendRequest方法,如下:
- 复制代码
- /**
- * Puts a new request in queue as a new thread in pool to be executed
- *
- * @param client HttpClient to be used for request, can differ in single requests
- * @param contentType MIME body type, for POST and PUT requests, may be null
- * @param context Context of Android application, to hold the reference of request
- * @param httpContext HttpContext in which the request will be executed
- * @param responseHandler ResponseHandler or its subclass to put the response into
- * @param uriRequest instance of HttpUriRequest, which means it must be of HttpDelete,
- * HttpPost, HttpGet, HttpPut, etc.
- * @return RequestHandle of future request process
- */
- protected RequestHandle sendRequest(DefaultHttpClient client, HttpContext httpContext, HttpUriRequest uriRequest,
- String contentType, ResponseHandlerInterface responseHandler, Context context) {
- if (uriRequest == null) {
- throw new IllegalArgumentException("HttpUriRequest must not be null");
- }
- if (responseHandler == null) {
- throw new IllegalArgumentException("ResponseHandler must not be null");
- }
- if (responseHandler.getUseSynchronousMode()) {
- throw new IllegalArgumentException("Synchronous ResponseHandler used in AsyncHttpClient. You should create your response handler in a looper thread or use SyncHttpClient instead.");
- }
- if (contentType != null) {
- uriRequest.setHeader(HEADER_CONTENT_TYPE, contentType);
- }
- responseHandler.setRequestHeaders(uriRequest.getAllHeaders());
- responseHandler.setRequestURI(uriRequest.getURI());
- // 下面的这3行是重点,创建请求,提交请求到线程池,将请求包装到RequestHandle用于之后的取消、管理
- AsyncHttpRequest request = newAsyncHttpRequest(client, httpContext, uriRequest, contentType, responseHandler, context);
- threadPool.submit(request); // 能submit说明request至少是个Runnable
- RequestHandle requestHandle = new RequestHandle(request);
- if (context != null) { // 如果Android context非空的话,做一些关联操作,后面可以通过context来取消request的执行
- // Add request to request map
- List<RequestHandle> requestList = requestMap.get(context);
- synchronized (requestMap) {
- if (requestList == null) {
- requestList = Collections.synchronizedList(new LinkedList<RequestHandle>());
- requestMap.put(context, requestList);
- }
- }
- if (responseHandler instanceof RangeFileAsyncHttpResponseHandler)
- ((RangeFileAsyncHttpResponseHandler) responseHandler).updateRequestHeaders(uriRequest);
- requestList.add(requestHandle);
- Iterator<RequestHandle> iterator = requestList.iterator();
- while (iterator.hasNext()) {
- if (iterator.next().shouldBeGarbageCollected()) {
- iterator.remove(); // 清理已经完成/取消了的请求
- }
- }
- }
- return requestHandle;
- }
看到了吧,发送请求的过程其实重点是创建请求,然后submit到线程池,剩下的事情就交给线程池自己处理了,我们只需要坐等被调用。
来看看创建请求的方法,代码如下:
- /**
- * Instantiate a new asynchronous HTTP request for the passed parameters.
- *
- * @param client HttpClient to be used for request, can differ in single requests
- * @param contentType MIME body type, for POST and PUT requests, may be null
- * @param context Context of Android application, to hold the reference of request
- * @param httpContext HttpContext in which the request will be executed
- * @param responseHandler ResponseHandler or its subclass to put the response into
- * @param uriRequest instance of HttpUriRequest, which means it must be of HttpDelete,
- * HttpPost, HttpGet, HttpPut, etc.
- * @return AsyncHttpRequest ready to be dispatched
- */
- protected AsyncHttpRequest newAsyncHttpRequest(DefaultHttpClient client, HttpContext httpContext, HttpUriRequest uriRequest, String contentType, ResponseHandlerInterface responseHandler, Context context) {
- return new AsyncHttpRequest(client, httpContext, uriRequest, responseHandler);
- }
紧接着我们看看AsyncHttpRequest的实现:
- /**
- * Internal class, representing the HttpRequest, done in asynchronous manner
- */
- public class AsyncHttpRequest implements Runnable { // 这就是submit到线程池的Runnable
- private final AbstractHttpClient client;
- private final HttpContext context;
- private final HttpUriRequest request;
- private final ResponseHandlerInterface responseHandler;
- private int executionCount;
- private boolean isCancelled;
- private boolean cancelIsNotified;
- private boolean isFinished;
- private boolean isRequestPreProcessed;
- public AsyncHttpRequest(AbstractHttpClient client, HttpContext context, HttpUriRequest request, ResponseHandlerInterface responseHandler) {
- this.client = client;
- this.context = context;
- this.request = request;
- this.responseHandler = responseHandler;
- }
- /**
- * This method is called once by the system when the request is about to be
- * processed by the system. The library makes sure that a single request
- * is pre-processed only once.
- *
- * Please note: pre-processing does NOT run on the main thread, and thus
- * any UI activities that you must perform should be properly dispatched to
- * the app's UI thread.
- *
- * @param request The request to pre-process
- */
- public void onPreProcessRequest(AsyncHttpRequest request) {
- // default action is to do nothing...
- }
- /**
- * This method is called once by the system when the request has been fully
- * sent, handled and finished. The library makes sure that a single request
- * is post-processed only once.
- *
- * Please note: post-processing does NOT run on the main thread, and thus
- * any UI activities that you must perform should be properly dispatched to
- * the app's UI thread.
- *
- * @param request The request to post-process
- */
- public void onPostProcessRequest(AsyncHttpRequest request) {
- // default action is to do nothing...
- }
- @Override
- public void run() { // 这是在线程池中执行的方法,我们重点看看
- if (isCancelled()) { // 检测,如果已经取消了则直接返回,下面的代码有好多次做这个检测,因为你永远不知道什么时候会被取消
- return; // 同时也说明了我们的Request是支持取消的
- }
- // Carry out pre-processing for this request only once.
- if (!isRequestPreProcessed) {
- isRequestPreProcessed = true;
- onPreProcessRequest(this); // callback接口,在一次请求中只调用一次
- }
- if (isCancelled()) { // 再次检查
- return;
- }
- if (responseHandler != null) {
- responseHandler.sendStartMessage(); // 发送开始请求消息
- }
- if (isCancelled()) { // 检查
- return;
- }
- try {
- makeRequestWithRetries(); // 带自动retry机制的请求
- } catch (IOException e) {
- if (!isCancelled() && responseHandler != null) {
- responseHandler.sendFailureMessage(0, null, null, e); // 在没取消的情况下,发送失败消息
- } else {
- Log.e("AsyncHttpRequest", "makeRequestWithRetries returned error, but handler is null", e);
- }
- }
- if (isCancelled()) { // 检查again
- return;
- }
- if (responseHandler != null) { // 没取消的情况下,发送完成消息
- responseHandler.sendFinishMessage();
- }
- if (isCancelled()) {
- return;
- }
- // Carry out post-processing for this request.
- onPostProcessRequest(this); // 处理了请求之后的callback
- isFinished = true; // 设置为true表示这个请求执行完毕了
- }
- private void makeRequest() throws IOException { // 发送一次请求
- if (isCancelled()) {
- return;
- }
- // Fixes #115
- if (request.getURI().getScheme() == null) {
- // subclass of IOException so processed in the caller
- throw new MalformedURLException("No valid URI scheme was provided");
- }
- // 执行请求获得response
- HttpResponse response = client.execute(request, context);
- if (isCancelled() || responseHandler == null) {
- return;
- }
- // Carry out pre-processing for this response.
- responseHandler.onPreProcessResponse(responseHandler, response); // 处理response前
- if (isCancelled()) {
- return;
- }
- // The response is ready, handle it.
- responseHandler.sendResponseMessage(response); // 发送获得的response
- if (isCancelled()) {
- return;
- }
- // Carry out post-processing for this response.
- responseHandler.onPostProcessResponse(responseHandler, response); // 处理response后
- }
- private void makeRequestWithRetries() throws IOException {
- boolean retry = true;
- IOException cause = null;
- HttpRequestRetryHandler retryHandler = client.getHttpRequestRetryHandler();
- try {
- while (retry) { // 注意这个循环,当retry为false的时候退出
- try {
- makeRequest();
- return; // 请求成功的话,直接返回
- } catch (UnknownHostException e) {
- // switching between WI-FI and mobile data networks can cause a retry which then results in an UnknownHostException
- // while the WI-FI is initialising. The retry logic will be invoked here, if this is NOT the first retry
- // (to assist in genuine cases of unknown host) which seems better than outright failure
- cause = new IOException("UnknownHostException exception: " + e.getMessage());
- retry = (executionCount > 0) && retryHandler.retryRequest(cause, ++executionCount, context);
- } catch (NullPointerException e) {
- // there's a bug in HttpClient 4.0.x that on some occasions causes
- // DefaultRequestExecutor to throw an NPE, see
- // http://code.google.com/p/android/issues/detail?id=5255
- cause = new IOException("NPE in HttpClient: " + e.getMessage());
- retry = retryHandler.retryRequest(cause, ++executionCount, context);
- } catch (IOException e) {
- if (isCancelled()) {
- // Eating exception, as the request was cancelled
- return;
- }
- cause = e;
- retry = retryHandler.retryRequest(cause, ++executionCount, context);
- }
- // 各种异常的情况下,计算retry,看还是否需要retry
- if (retry && (responseHandler != null)) { // 需要retry的时候,发送retry消息并附带第几次retry了
- responseHandler.sendRetryMessage(executionCount);
- }
- }
- } catch (Exception e) {
- // catch anything else to ensure failure message is propagated
- Log.e("AsyncHttpRequest", "Unhandled exception origin cause", e);
- // 其他的所有不在上述catch里的异常都在这里统一包装成IOException,在最后抛出
- cause = new IOException("Unhandled exception: " + e.getMessage());
- }
- // cleaned up to throw IOException
- throw (cause); // 抛出,以便上层代码知道发生了什么
- }
- public boolean isCancelled() {
- if (isCancelled) {
- sendCancelNotification();
- }
- return isCancelled;
- }
- private synchronized void sendCancelNotification() {
- if (!isFinished && isCancelled && !cancelIsNotified) {
- cancelIsNotified = true;
- if (responseHandler != null)
- responseHandler.sendCancelMessage();
- }
- }
- public boolean isDone() {
- return isCancelled() || isFinished;
- }
- public boolean cancel(boolean mayInterruptIfRunning) {
- isCancelled = true;
- request.abort();
- return isCancelled();
- }
- }
紧接着,我们大概提下RequestHandle,它只是一个持有AsyncHttpRequest对象的弱引用,其方法内部都delegate给了AsyncHttpRequest,
非常简单,感兴趣的同学可自行阅读。
看完了Request,接下来该看看各种Response了,他们都实现了ResponseHandlerInterface接口,这里我们重点看下AsyncHttpResponseHandler,
因为它是后面所有更具体的子类的基础,其ctor代码如下:
- /**
- * Creates a new AsyncHttpResponseHandler
- */
- public AsyncHttpResponseHandler() { // 不指定looper
- this(null);
- }
- /**
- * Creates a new AsyncHttpResponseHandler with a user-supplied looper. If
- * the passed looper is null, the looper attached to the current thread will
- * be used.
- *
- * @param looper The looper to work with
- */
- public AsyncHttpResponseHandler(Looper looper) { // 如果没指定looper的话,会用当前线程的looper顶替
- this.looper = looper == null ? Looper.myLooper() : looper;
- // Use asynchronous mode by default.
- setUseSynchronousMode(false); // 默认是异步的方式,这里异步的意思是指对response的处理发生在与looper
- } // 关联的线程中,而不是请求发生的线程池里的线程中
- @Override
- public void setUseSynchronousMode(boolean sync) {
- // A looper must be prepared before setting asynchronous mode.
- if (!sync && this.looper == null) {
- sync = true; // 一种错误的情况,强制使用同步mode
- Log.w(LOG_TAG, "Current thread has not called Looper.prepare(). Forcing synchronous mode.");
- }
- // If using asynchronous mode.
- if (!sync && handler == null) { // 初始化handler
- // Create a handler on current thread to submit tasks
- handler = new ResponderHandler(this, this.looper);
- } else if (sync && handler != null) {
- // TODO: Consider adding a flag to remove all queued messages.
- handler = null;
- }
- useSynchronousMode = sync;
- }
一般来说,我们会直接在UI线程中调用无参版本的ctor,也就是说response是和UI线程关联的,所有对其的处理handleMessage是发生
在UI线程中的。如果你想用response的结果来更新UI则这是正确的方式。
接着我们看看和处理response相关的代码:
- /**
- * Avoid leaks by using a non-anonymous handler class.
- */
- private static class ResponderHandler extends Handler {
- private final AsyncHttpResponseHandler mResponder;
- ResponderHandler(AsyncHttpResponseHandler mResponder, Looper looper) {
- super(looper);
- this.mResponder = mResponder;
- }
- @Override
- public void handleMessage(Message msg) { // 一个简单的Handler,其handleMessage delegate给了mResponder
- mResponder.handleMessage(msg);
- }
- }
- // Methods which emulate android's Handler and Message methods
- protected void handleMessage(Message message) { // 对各种message的处理,回调各种onXXX方法
- Object[] response;
- switch (message.what) {
- case SUCCESS_MESSAGE:
- response = (Object[]) message.obj;
- if (response != null && response.length >= 3) {
- onSuccess((Integer) response[0], (Header[]) response[1], (byte[]) response[2]);
- } else {
- Log.e(LOG_TAG, "SUCCESS_MESSAGE didn't got enough params");
- }
- break;
- case FAILURE_MESSAGE:
- response = (Object[]) message.obj;
- if (response != null && response.length >= 4) {
- onFailure((Integer) response[0], (Header[]) response[1], (byte[]) response[2], (Throwable) response[3]);
- } else {
- Log.e(LOG_TAG, "FAILURE_MESSAGE didn't got enough params");
- }
- break;
- case START_MESSAGE:
- onStart();
- break;
- case FINISH_MESSAGE:
- onFinish();
- break;
- case PROGRESS_MESSAGE:
- response = (Object[]) message.obj;
- if (response != null && response.length >= 2) {
- try {
- onProgress((Integer) response[0], (Integer) response[1]);
- } catch (Throwable t) {
- Log.e(LOG_TAG, "custom onProgress contains an error", t);
- }
- } else {
- Log.e(LOG_TAG, "PROGRESS_MESSAGE didn't got enough params");
- }
- break;
- case RETRY_MESSAGE:
- response = (Object[]) message.obj;
- if (response != null && response.length == 1) {
- onRetry((Integer) response[0]);
- } else {
- Log.e(LOG_TAG, "RETRY_MESSAGE didn't get enough params");
- }
- break;
- case CANCEL_MESSAGE:
- onCancel();
- break;
- }
- }
- protected void sendMessage(Message msg) {
- if (getUseSynchronousMode() || handler == null) {
- handleMessage(msg); // 如果是同步的方式,则handleMessage发生在调用sendMessage的线程中
- } else if (!Thread.currentThread().isInterrupted()) { // do not send messages if request has been cancelled
- handler.sendMessage(msg); // 否则发生在与handler关联的线程中,一般多为UI线程
- }
- }
代码中各种sendXXXMessage都会调用这里的sendMessage方法,只是构造的msg的what、obj不同而已。而sendXXXMessage方法
会在request的不同阶段自动被调用,详见AsyncHttpRequest中。下一步我们看眼对response的解析过程,代码如下:
- @Override
- public void sendResponseMessage(HttpResponse response) throws IOException {
- // do not process if request has been cancelled
- if (!Thread.currentThread().isInterrupted()) {
- StatusLine status = response.getStatusLine();
- byte[] responseBody;
- responseBody = getResponseData(response.getEntity()); // 将response解析成字节数组
- // additional cancellation check as getResponseData() can take non-zero time to process
- if (!Thread.currentThread().isInterrupted()) {
- if (status.getStatusCode() >= 300) { // 标志失败的情况
- sendFailureMessage(status.getStatusCode(), response.getAllHeaders(), responseBody, new HttpResponseException(status.getStatusCode(), status.getReasonPhrase()));
- } else { // 成功的情况
- sendSuccessMessage(status.getStatusCode(), response.getAllHeaders(), responseBody);
- }
- }
- }
- }
- /**
- * Returns byte array of response HttpEntity contents
- *
- * @param entity can be null
- * @return response entity body or null
- * @throws java.io.IOException if reading entity or creating byte array failed
- */
- byte[] getResponseData(HttpEntity entity) throws IOException {
- byte[] responseBody = null;
- if (entity != null) {
- InputStream instream = entity.getContent(); // 从entity中读取字节流
- if (instream != null) {
- long contentLength = entity.getContentLength();
- if (contentLength > Integer.MAX_VALUE) {
- throw new IllegalArgumentException("HTTP entity too large to be buffered in memory");
- }
- int buffersize = (contentLength <= 0) ? BUFFER_SIZE : (int) contentLength;
- try {
- ByteArrayBuffer buffer = new ByteArrayBuffer(buffersize);
- try {
- byte[] tmp = new byte[BUFFER_SIZE];
- int l, count = 0;
- // do not send messages if request has been cancelled
- while ((l = instream.read(tmp)) != -1 && !Thread.currentThread().isInterrupted()) {
- count += l;
- buffer.append(tmp, 0, l);
- sendProgressMessage(count, (int) (contentLength <= 0 ? 1 : contentLength));
- }
- } finally {
- AsyncHttpClient.silentCloseInputStream(instream);
- AsyncHttpClient.endEntityViaReflection(entity);
- }
- responseBody = buffer.toByteArray();
- } catch (OutOfMemoryError e) {
- System.gc();
- throw new IOException("File too large to fit into available memory");
- }
- }
- }
- return responseBody;
- }
onXXX方法除了onSuccess和onFailure外都做了默认实现即啥也不做,所以继承至它的子类至少要实现这2个方法,其他的方法你可以选择性实现。
接下来我们看看TextHttpResponseHandler子类的实现,关键代码如下:
- @Override // 对上述2个方法的重载,其中将byte[]通过getResponseString方法转化成了String对象
- public void onSuccess(int statusCode, Header[] headers, byte[] responseBytes) {
- onSuccess(statusCode, headers, getResponseString(responseBytes, getCharset()));
- }
- @Override
- public void onFailure(int statusCode, Header[] headers, byte[] responseBytes, Throwable throwable) {
- onFailure(statusCode, headers, getResponseString(responseBytes, getCharset()), throwable);
- }
- /**
- * Attempts to encode response bytes as string of set encoding
- *
- * @param charset charset to create string with
- * @param stringBytes response bytes
- * @return String of set encoding or null
- */
- public static String getResponseString(byte[] stringBytes, String charset) {
- try {
- String toReturn = (stringBytes == null) ? null : new String(stringBytes, charset);
- if (toReturn != null && toReturn.startsWith(UTF8_BOM)) {
- return toReturn.substring(1);
- }
- return toReturn;
- } catch (UnsupportedEncodingException e) {
- Log.e(LOG_TAG, "Encoding response into string failed", e);
- return null;
- }
- }
说白了,也就是在父类基础上多了一层处理,将byte[]根据特定的编码转化成String而已,类似的JsonHttpResponseHandler又在此基础上
将String转化成JSONObject或JSONArray,细节不赘述。
ResponseHandler介绍完了,这里我们提下RetryHandler,这个类也很简单,根据内部的白/黑名单等规则来确定是否要retry。
AsyncHttpClient当然也提供了对Cookie的支持,默认是保存在Android的SharedPreferences中,具体代码见PersistentCookieStore。
还有一个功能丰富的RequestParams类,据此你不仅可以为GET/POST方法提供参数,甚至你可以上传本地文件到server端。
到此为止,AsyncHttpClient关键部分的代码已基本分析完毕了,剩下的还需要大家自己在项目中多多实践,
本文链接:http://www.cnblogs.com/xiaoweiz/p/3918042.html