1. Okhttp基本使用
初始化可以添加自定义的拦截器
OkHttpClient okHttpClient = new OkHttpClient.Builder()
.connectTimeout(30, TimeUnit.SECONDS)
.writeTimeout(30, TimeUnit.SECONDS)
.readTimeout(30, TimeUnit.SECONDS)
.addInterceptor(interceptorImpl).builder();//创建OKHttpClient的Builder
基本使用
String url = "http://wwww.baidu.com";
final Request request = new Request.Builder()
.url(url)
.get()//默认就是GET请求，可以不写
.build();
Call call = okHttpClient.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
Log.d(TAG, "onFailure: ");
}
@Override
public void onResponse(Call call, Response response) throws IOException {
Log.d(TAG, "onResponse: " + response.body().string());
}
});
一般的使用大致就是这样的
2.从OkHttpClient创建开始入手分析
OkHttpClient.Builder()使用builder模式，用户可以自定义相应的参数
开发一般会用到的是
.connectTimeout(30, TimeUnit.SECONDS)
.writeTimeout(30, TimeUnit.SECONDS)
.readTimeout(30, TimeUnit.SECONDS)
.addInterceptor(interceptorImpl)
连接时间，写时间，读时间以及对应的Interceptor相关的拦截器
3.构建Request
Request用的也是Builder模式，好处主要是可以动态配置相应的参数
Request(Builder builder) {
this.url = builder.url;
this.method = builder.method;
this.headers = builder.headers.build();
this.body = builder.body;
this.tags = Util.immutableMap(builder.tags);
}
tag主要是做标识的，请求返回为null时候的标识操作
4.构建Call
构建Call,主要是调用RealCall.newRealCall方法，并在其内部添加了一个事件回调监听
/**
* Prepares the {@code request} to be executed at some point in the future.
*/
@Override public Call newCall(Request request) {
return RealCall.newRealCall(this, request, false /* for web socket */);
}
//RealCall
static RealCall newRealCall(OkHttpClient client, Request originalRequest, boolean forWebSocket) {
// Safely publish the Call instance to the EventListener.
RealCall call = new RealCall(client, originalRequest, forWebSocket);
//添加一个事件回调，后续会有用处
call.eventListener = client.eventListenerFactory().create(call);
return call;
}
而在newRealCall方法中同时也调用了RealCall的构造方法
构造方法中加入了RetryAndFollowUpInterceptor重试拦截器，okhttp中加入了很多拦截器，这也是一大特色
private RealCall(OkHttpClient client, Request originalRequest, boolean forWebSocket) {
this.client = client;
this.originalRequest = originalRequest;
this.forWebSocket = forWebSocket;
this.retryAndFollowUpInterceptor = new RetryAndFollowUpInterceptor(client, forWebSocket);
}
5. 执行异步请求enqueue
@Override public void enqueue(Callback responseCallback) {
synchronized (this) {
if (executed) throw new IllegalStateException("Already Executed");
executed = true;
}
captureCallStackTrace();
eventListener.callStart(this);
client.dispatcher().enqueue(new AsyncCall(responseCallback));
}
executed以及synchronized主要是用来防止重复操作和多线程同步用的
接下来的方法
private void captureCallStackTrace() {
Object callStackTrace = Platform.get().getStackTraceForCloseable("response.body().close()");
retryAndFollowUpInterceptor.setCallStackTrace(callStackTrace);
}
重试监听器做一些栈StackTrace记录，以及eventListener.callStart(this);事件监听做回调处理，不影响流程
接着就到了Dispatcher的enqueue方法
/** Ready async calls in the order they'll be run. */
private final Deque<AsyncCall> readyAsyncCalls = new ArrayDeque<>();
/** Running asynchronous calls. Includes canceled calls that haven't finished yet. */
private final Deque<AsyncCall> runningAsyncCalls = new ArrayDeque<>();
/** Running synchronous calls. Includes canceled calls that haven't finished yet. */
private final Deque<RealCall> runningSyncCalls = new ArrayDeque<>();
synchronized void enqueue(AsyncCall call) {
if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) {
runningAsyncCalls.add(call);
executorService().execute(call);
} else {
readyAsyncCalls.add(call);
}
}
Dispatcher中定义三个队列分别是readyAsyncCalls异步等待，同步运行runningAsyncCalls以及runningSyncCalls异步运行队列，enqueue方法中，当运行异步队列个数小于最大请求数(64)并且同一Host请求个数小于maxRequestsPerHost(5)则加入异步运行队列，并且用线程执行，否则加入异步等待队列中，这是okhttp的线程队列优化
6.查看AsyncCall的run方法
AsyncCall 继承了NamedRunnable，其内部会run方法会调用execute()，代码如下
@Override protected void execute() {
boolean signalledCallback = false;
try {
Response response = getResponseWithInterceptorChain();
if (retryAndFollowUpInterceptor.isCanceled()) {
signalledCallback = true;
responseCallback.onFailure(RealCall.this, new IOException("Canceled"));
} else {
signalledCallback = true;
responseCallback.onResponse(RealCall.this, response);
}
} catch (IOException e) {
if (signalledCallback) {
// Do not signal the callback twice!
Platform.get().log(INFO, "Callback failure for " + toLoggableString(), e);
} else {
eventListener.callFailed(RealCall.this, e);
responseCallback.onFailure(RealCall.this, e);
}
} finally {
client.dispatcher().finished(this);
}
}
}
signalledCallback这个标识用来处理是否打印对应的日志，这里可以看到Response类，说明网络请求是在getResponseWithInterceptorChain中完成的，之后会回调当前的Call状态值
7.真正的网络请求的getResponseWithInterceptorChain
Response getResponseWithInterceptorChain() throws IOException {
// Build a full stack of interceptors.
List<Interceptor> interceptors = new ArrayList<>();
interceptors.addAll(client.interceptors());
//失败重试拦截器
interceptors.add(retryAndFollowUpInterceptor);
//request和response拦截器
interceptors.add(new BridgeInterceptor(client.cookieJar()));
//缓存拦截器
interceptors.add(new CacheInterceptor(client.internalCache()));
//网络请求连接拦截器
interceptors.add(new ConnectInterceptor(client));
if (!forWebSocket) {
//网络拦截器
interceptors.addAll(client.networkInterceptors());
}
//实际网络请求的拦截器
interceptors.add(new CallServerInterceptor(forWebSocket));
Interceptor.Chain chain = new RealInterceptorChain(interceptors, null, null, null, 0,
originalRequest, this, eventListener, client.connectTimeoutMillis(),
client.readTimeoutMillis(), client.writeTimeoutMillis());
return chain.proceed(originalRequest);
}
加入各式各样的拦截器，各个拦截器之间不耦合，易于用户的自己配置，最后调用RealInterceptorChain的proceed方法
8.RealInterceptorChain的proceed方法
public RealInterceptorChain(List<Interceptor> interceptors, StreamAllocation streamAllocation,
HttpCodec httpCodec, RealConnection connection, int index, Request request, Call call,
EventListener eventListener, int connectTimeout, int readTimeout, int writeTimeout) {
this.interceptors = interceptors;
this.connection = connection;
this.streamAllocation = streamAllocation;
this.httpCodec = httpCodec;
this.index = index;
this.request = request;
this.call = call;
this.eventListener = eventListener;
this.connectTimeout = connectTimeout;
this.readTimeout = readTimeout;
this.writeTimeout = writeTimeout;
}
public Response proceed(Request request, StreamAllocation streamAllocation, HttpCodec httpCodec,
RealConnection connection) throws IOException {
if (index >= interceptors.size()) throw new AssertionError();
calls++;
//...
// Call the next interceptor in the chain.
RealInterceptorChain next = new RealInterceptorChain(interceptors, streamAllocation, httpCodec,
connection, index + 1, request, call, eventListener, connectTimeout, readTimeout,
writeTimeout);
Interceptor interceptor = interceptors.get(index);
Response response = interceptor.intercept(next);
// .....
return response;
}
构造方法中加入了eventListener事件监听，看来okhttp中eventListener的监听一直延伸到这里，还加入了
this.connectTimeout = connectTimeout;
this.readTimeout = readTimeout;
this.writeTimeout = writeTimeout;
连接时间的配置
要重点关注的是index这个字段，前面传进来的时候，默认是0，而在proceed方法中，又重新执行了RealInterceptorChain的构造方法，并通过 interceptors.get(index)获取下一个拦截器，并且执行interceptor.intercept(next)方法，随便找一个拦截器看看
public final class BridgeInterceptor implements Interceptor {
@Override public Response intercept(Chain chain) throws IOException {
//省略部分代码
Response networkResponse = chain.proceed(requestBuilder.build());
//省略部分代码
return responseBuilder.build();
}
}
拦截器内部又重新调用了chain.proceed的方法，这和递归操作类似，也是okHttp最经典的责任链模式。
9.同步操作
@Override public Response execute() throws IOException {
synchronized (this) {
if (executed) throw new IllegalStateException("Already Executed");
executed = true;
}
captureCallStackTrace();
eventListener.callStart(this);
try {
client.dispatcher().executed(this);
Response result = getResponseWithInterceptorChain();
if (result == null) throw new IOException("Canceled");
return result;
} catch (IOException e) {
eventListener.callFailed(this, e);
throw e;
} finally {
client.dispatcher().finished(this);
}
}
同步请求也是通过getResponseWithInterceptorChain来完成的，流程更简单
10.大致的流程图
image
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