首先讲讲okHttp吧，okhttp算是对于android原生请求的升级，有从TCP连接建立，到ssl建立（就是https），http请求报文等缓存，重试等功能，让我们更加方便快捷的进行http请求，因为实在太优秀了，已经被android收录在新版中了。所以相较于Retrofit来说，OkHttp更加面向底层一些，Retrofit用的也是OkHttp做请求的。Retrofit的源码结构看这篇Retrofit从使用到原理。如果大家懂一点HTTP的相关知识，这样看起源码会更加简单，或者说熟悉。下面有一些http相关知识可以先看一下：
Android网络请求知识（一）HTTP基础概念
Android网络请求知识（二）对称和非对称加密、数字签名，Hash，Base64编码
Android网络请求知识（三）授权，TCP/IP，HTTPS建立过程
对于优秀的OkHttp，当然值得我们去学习一下。
使用OkHttp
简单的使用，重点在源码的分析，知道步骤就可以。
//创建OkHttp
OkHttpClient okHttpClient = new OkHttpClient.Builder().build();
//创建请求
Request request = new Request.Builder()
.url("http://www.baidu.com")
.build();
Call call = okHttpClient.newCall(request);
//进入队列等待执行
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
Log.i(TAG, "onFailure: ");
}
@Override
public void onResponse(Call call, Response response) throws IOException {
Log.i(TAG, "onResponse: ");
}
});
创建了一个怎样的OkHttpClient呢？
我们一步步的跟进源码最后发现会将Buider中一系列参数赋值给我们的okHttpClient的对象，看到这些参数有点多，如果对http的内容有了解，耐心看就会熟悉的感觉，先介绍一下其中的一些参数：
public static final class Builder {
Dispatcher dispatcher;
@Nullable Proxy proxy;
List<Protocol> protocols;
List<ConnectionSpec> connectionSpecs;
final List<Interceptor> interceptors = new ArrayList<>();
final List<Interceptor> networkInterceptors = new ArrayList<>();
EventListener.Factory eventListenerFactory;
ProxySelector proxySelector;
CookieJar cookieJar;
@Nullable Cache cache;
@Nullable InternalCache internalCache;
SocketFactory socketFactory;
@Nullable SSLSocketFactory sslSocketFactory;
@Nullable CertificateChainCleaner certificateChainCleaner;
HostnameVerifier hostnameVerifier;
CertificatePinner certificatePinner;
Authenticator proxyAuthenticator;
Authenticator authenticator;
ConnectionPool connectionPool;
Dns dns;
boolean followSslRedirects;
boolean followRedirects;
boolean retryOnConnectionFailure;
int connectTimeout;
int readTimeout;
int writeTimeout;
int pingInterval;
.......
}
- Dispatcher 先看一下源码吧，会有熟悉的感觉。Dispatcher作为调度器，内部有线程池，存储准备执行异步请求队列readyAsyncCalls，存储正在执行异步请求的队列runningAsyncCalls 等等，发现有maxRequests最大请求数，maxRequestsPerHost每个host同时最大的请求数量，Dispatcher控制着后台的网络请求。
public final class Dispatcher {
private int maxRequests = 64;
private int maxRequestsPerHost = 5;
private @Nullable Runnable idleCallback;
/** Executes calls. Created lazily. */
private @Nullable ExecutorService executorService;
/** 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<>();
public Dispatcher(ExecutorService executorService) {
this.executorService = executorService;
}
public synchronized ExecutorService executorService() {
if (executorService == null) {
executorService = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>(), Util.threadFactory("OkHttp Dispatcher", false));
}
return executorService;
}
......
}
- Proxy 代理设置 相当于完全信任的中间代理
- List<Protocol> protocols 支持的具体http协议，有http/1.0，http/1.1，http/2.0，spdy等
- List<ConnectionSpec> connectionSpecs https连接中CipherSuite的相关内容，okhttp支持的使用https时TLS等，支持的对称加密，非对称加密，hash算法
- interceptors，networkInterceptors 这两个是okhttp中重要的拦截链的概念，后面介绍。这两个拦截器是可以用户自己配置的，一个在前面一个在后面
- EventListener.Factory eventListenerFactory 一个Call的状态监听器，记录过程
- proxySelector 使用默认的代理选择器
- CookieJar cookie管理器，默认没有，我们知道http是无状态的，所以需要okhttp提供对cookie的支持。如果使用需要实现saveFromResponse和loadForRequest两个方法。
- Cache cache缓存的存储配置，默认没有。如果需要用，自己填写存储文件位置以及存储空间大小。
- SocketFactory 使用默认的Socket工厂产生Socket，TCP传输层有关，三次握手
- SSLSocketFactory 带上ssl的socket的工厂，就是整个https连接的过程
- hostnameVerifier 主机名验证，https连接建立中，服务器发来证书中的host与客户端需要访问host的验证。
- certificatePinner 证书锁定，使用CertificatePinner来约束哪些认证机构被信任，下面详细介绍
- authenticator 401 没登录没权限自动回调。
new OkHttpClient.Builder()
.authenticator(new Authenticator() {
@Nullable
@Override
public Request authenticate(Route route, Response response) throws IOException {
//request 请求获取token或者刷新token
return response.request().newBuilder()
.addHeader("Authorizaion","Besic base64(psw)")
.build();
}
})
- connectionPool 连接池
- dns 根据域名获得IP列表
- followSslRedirects 在重定向时，是否自动follow（http重定向https，或者https重定向http）
- followRedirects 在重定向时，是否自动follow（http之间）
- retryOnConnectionFailure 在请求失败后是否自动重试，适用同一个域名多个IP切换的重试
- connectTimeout 连接超时时间
- readTimeout 读取响应数据超时时间
- writeTimeout 向服务器写入数据超时时间
- pingInterval 心跳连接的间隔时间，websocket中用保持http的连接
certificatePinner使用，锁定证书
请求https://publicobject.com是需要证书的，我们没有证书就添加一个sha1/AAAAAAAAAAAAAAAAAAAAAAAAAAA=来做为证书进行请求。
String hostname = "publicobject.com";
CertificatePinner certificatePinner = new CertificatePinner.Builder()
.add(hostname, "sha1/AAAAAAAAAAAAAAAAAAAAAAAAAAA=")
.build();
OkHttpClient okHttpClient = new OkHttpClient.Builder()
.certificatePinner(certificatePinner)
.build();
Request request = new Request.Builder()
.url("https://" + hostname)
.build();
Call call = okHttpClient.newCall(request);
//进入队列等待执行
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
Log.i(TAG, "onFailure: " + e.toString());
e.printStackTrace();
}
@Override
public void onResponse(Call call, Response response) throws IOException {
Log.i(TAG, "onResponse: ");
}
});
得到下面的消息，告诉我们的证书错了，同时发现有三个证书，这就我们需要固定的三个证书
10-31 17:34:49.508 29471-30425/com.example.chenpeng.julyapplication I/OkHttp: onFailure: javax.net.ssl.SSLPeerUnverifiedException: Certificate pinning failure!
Peer certificate chain:
sha256/afwiKY3RxoMmLkuRW1l7QsPZTJPwDS2pdDROQjXw8ig=: CN=publicobject.com,OU=PositiveSSL,OU=Domain Control Validated
sha256/klO23nT2ehFDXCfx3eHTDRESMz3asj1muO+4aIdjiuY=: CN=COMODO RSA Domain Validation Secure Server CA,O=COMODO CA Limited,L=Salford,ST=Greater Manchester,C=GB
sha256/grX4Ta9HpZx6tSHkmCrvpApTQGo67CYDnvprLg5yRME=: CN=COMODO RSA Certification Authority,O=COMODO CA Limited,L=Salford,ST=Greater Manchester,C=GB
Pinned certificates for publicobject.com:
sha1/AAAAAAAAAAAAAAAAAAAAAAAAAAA=
10-31 17:34:49.509 29471-30425/com.example.chenpeng.julyapplication W/System.err: javax.net.ssl.SSLPeerUnverifiedException: Certificate pinning failure!
10-31 17:34:49.509 29471-30425/com.example.chenpeng.julyapplication W/System.err: Peer certificate chain:
10-31 17:34:49.509 29471-30425/com.example.chenpeng.julyapplication W/System.err: sha256/afwiKY3RxoMmLkuRW1l7QsPZTJPwDS2pdDROQjXw8ig=: CN=publicobject.com,OU=PositiveSSL,OU=Domain Control Validated
10-31 17:34:49.509 29471-30425/com.example.chenpeng.julyapplication W/System.err: sha256/klO23nT2ehFDXCfx3eHTDRESMz3asj1muO+4aIdjiuY=: CN=COMODO RSA Domain Validation Secure Server CA,O=COMODO CA Limited,L=Salford,ST=Greater Manchester,C=GB
10-31 17:34:49.509 29471-30425/com.example.chenpeng.julyapplication W/System.err: sha256/grX4Ta9HpZx6tSHkmCrvpApTQGo67CYDnvprLg5yRME=: CN=COMODO RSA Certification Authority,O=COMODO CA Limited,L=Salford,ST=Greater Manchester,C=GB
10-31 17:34:49.509 29471-30425/com.example.chenpeng.julyapplication W/System.err: Pinned certificates for publicobject.com:
10-31 17:34:49.509 29471-30425/com.example.chenpeng.julyapplication W/System.err: sha1/AAAAAAAAAAAAAAAAAAAAAAAAAAA=
10-31 17:34:49.516 29471-30425/com.example.chenpeng.julyapplication W/System.err: at okhttp3.CertificatePinner.check(CertificatePinner.java:204)
这就是证书固定，将应用的可信 CA 限制在一个很小的 CA 集范围内，其实我们只要其中一个就可以。证书锁定增加了安全性，但限制了服务器升级TLS证书的能力。
CertificatePinner certificatePinner = new CertificatePinner.Builder()
.add(hostname, "sha256/afwiKY3RxoMmLkuRW1l7QsPZTJPwDS2pdDROQjXw8ig=")
.add(hostname,"sha256/klO23nT2ehFDXCfx3eHTDRESMz3asj1muO+4aIdjiuY=")
.add(hostname,"sha256/grX4Ta9HpZx6tSHkmCrvpApTQGo67CYDnvprLg5yRME=")
.build();
创建Request做了什么操作？
跟进源码，赋值一些构建http请求的内容，url，请求方法，请求头，请求体等内容。
Request(Builder builder) {
this.url = builder.url;
this.method = builder.method;
this.headers = builder.headers.build();
this.body = builder.body;
this.tag = builder.tag != null ? builder.tag : this;
}
Call
跟进okHttpClient.newCall(request)，创建一个RealCall
@Override public Call newCall(Request request) {
return RealCall.newRealCall(this, request, false /* for web socket */);
}
RealCall的异步执行
RealCall调用enqueue方法，client.dispatcher().enqueue(new AsyncCall(responseCallback))中包装一个AsyncCall。跟一下client.dispatcher().enqueue方法：
@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));
}
Dispatcher调度器的enqueue方法，发现了当请求数小于64个并且每个host的请求数小于5个加入runningAsyncCalls的队列并且执行线程AsyncCall，否则加入readyAsyncCalls队列。
synchronized void enqueue(AsyncCall call) {
if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) {
runningAsyncCalls.add(call);
executorService().execute(call);
} else {
readyAsyncCalls.add(call);
}
}
看一下AsyncCall的结构以及执行方法，继承一个NamedRunnable，在execute方法中，getResponseWithInterceptorChain()通过一系列的拦截链获得Response，然后根据不同的情况回调Callback 的onFailure，onResponse方法。
final class AsyncCall extends NamedRunnable {
private final Callback responseCallback;
AsyncCall(Callback responseCallback) {
super("OkHttp %s", redactedUrl());
this.responseCallback = responseCallback;
}
String host() {
return originalRequest.url().host();
}
Request request() {
return originalRequest;
}
RealCall get() {
return RealCall.this;
}
@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);
}
}
}
通过getResponseWithInterceptorChain()，介绍OKhttp的拦截链
拦截链会经过retryAndFollowUpInterceptor等多个拦截器，有些可以是我们自己定义的，有些是给WebSocket的请求使用的，最终组成一个RealInterceptorChain，用proceed方法去执行发起请求和获得响应。在RealInterceptorChain中，多个Interceptor会依次调用自己的intercept方法：对请求Request进行预处理；重新调用proceed()把请求交给下一个Interceptor；在下一个Interceptor处理完成并返回之后，对Response进行后续处理。下面一个一个介绍拦截器：
Response getResponseWithInterceptorChain() throws IOException {
// Build a full stack of interceptors.
List<Interceptor> interceptors = new ArrayList<>();
interceptors.addAll(client.interceptors());
interceptors.add(retryAndFollowUpInterceptor);
interceptors.add(new BridgeInterceptor(client.cookieJar()));
interceptors.add(new CacheInterceptor(client.internalCache()));
interceptors.add(new ConnectInterceptor(client));
if (!forWebSocket) {
interceptors.addAll(client.networkInterceptors());
}
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);
}
画一个流程图，方便记忆和理解，蓝底的拦截器是一定会在拦截器链中出现的，白底的的拦截器根据自己的配置和不同的请求不一定会出现。下面具体介绍每个拦截器。
拦截链流程图.png
client.interceptors()
通过addInterceptor(Interceptor)设置，在所有拦截器之前，所以用来做最早的预处理，以及最后的response的扫尾工作。代码中一般这样用
OkHttpClient okHttpClient = new OkHttpClient.Builder()
.addInterceptor(new Interceptor() {
@Override
public Response intercept(Chain chain) throws IOException {
//前置工作
Response response = chain.proceed(chain.request());
//后置工作
return response;
}
})
.build();
RetryAndFollowUpInterceptor 是否需要重新请求
找到重点的代码：response = realChain.proceed(request, streamAllocation, null, null)。在这行之前的就是对request请求的预处理，proceed()方法使Interceptor往下走同时获得下一个Interceptor返回的原始Response，在这行之后的就是对response内容处理。重点也是在proceed方法后面。
RetryAndFollowUpInterceptor作用：是否需要重新请求。当然是根据response的结果来判断，看源码发现request也没有做什么特别的操作。看到Request followUp = followUpRequest(response, streamAllocation.route())，这就是新的请求，在一个while(true)的无限循环中。在下一行有一个判断，如果followUp为null，就直接返回response不需要再重新请求，后面也有很多的跳出这个循环的情况：比如重发请求的次数大于规定的次数（MAX_FOLLOW_UPS）等
@Override public Response intercept(Chain chain) throws IOException {
Request request = chain.request();
RealInterceptorChain realChain = (RealInterceptorChain) chain;
Call call = realChain.call();
EventListener eventListener = realChain.eventListener();
StreamAllocation streamAllocation = new StreamAllocation(client.connectionPool(),
createAddress(request.url()), call, eventListener, callStackTrace);
this.streamAllocation = streamAllocation;
int followUpCount = 0;
Response priorResponse = null;
while (true) {
if (canceled) {
streamAllocation.release();
throw new IOException("Canceled");
}
Response response;
boolean releaseConnection = true;
try {
response = realChain.proceed(request, streamAllocation, null, null);
releaseConnection = false;
} catch (RouteException e) {
// The attempt to connect via a route failed. The request will not have been sent.
if (!recover(e.getLastConnectException(), streamAllocation, false, request)) {
throw e.getLastConnectException();
}
releaseConnection = false;
continue;
} catch (IOException e) {
// An attempt to communicate with a server failed. The request may have been sent.
boolean requestSendStarted = !(e instanceof ConnectionShutdownException);
if (!recover(e, streamAllocation, requestSendStarted, request)) throw e;
releaseConnection = false;
continue;
} finally {
// We're throwing an unchecked exception. Release any resources.
if (releaseConnection) {
streamAllocation.streamFailed(null);
streamAllocation.release();
}
}
// Attach the prior response if it exists. Such responses never have a body.
if (priorResponse != null) {
response = response.newBuilder()
.priorResponse(priorResponse.newBuilder()
.body(null)
.build())
.build();
}
Request followUp = followUpRequest(response, streamAllocation.route());
if (followUp == null) {
if (!forWebSocket) {
streamAllocation.release();
}
return response;
}
closeQuietly(response.body());
if (++followUpCount > MAX_FOLLOW_UPS) {
streamAllocation.release();
throw new ProtocolException("Too many follow-up requests: " + followUpCount);
}
if (followUp.body() instanceof UnrepeatableRequestBody) {
streamAllocation.release();
throw new HttpRetryException("Cannot retry streamed HTTP body", response.code());
}
if (!sameConnection(response, followUp.url())) {
streamAllocation.release();
streamAllocation = new StreamAllocation(client.connectionPool(),
createAddress(followUp.url()), call, eventListener, callStackTrace);
this.streamAllocation = streamAllocation;
} else if (streamAllocation.codec() != null) {
throw new IllegalStateException("Closing the body of " + response
+ " didn't close its backing stream. Bad interceptor?");
}
request = followUp;
priorResponse = response;
}
}
BridgeInterceptor 添加http请求头相关内容
在chain.proceed()之前，代码中有一些熟悉的内容：Content-Type，Content-Length，Host，Cookie等。这些都是http中请求头的内容，包括根据url在cookieJar中寻找cookie添加到请求头中。
在chain.proceed()之后，对于返回的response会存储相关cookie，对gzip压缩数据的解包等操作。对于cookiejar需要自己实现存取。
@Override public Response intercept(Chain chain) throws IOException {
Request userRequest = chain.request();
Request.Builder requestBuilder = userRequest.newBuilder();
RequestBody body = userRequest.body();
if (body != null) {
MediaType contentType = body.contentType();
if (contentType != null) {
requestBuilder.header("Content-Type", contentType.toString());
}
long contentLength = body.contentLength();
if (contentLength != -1) {
requestBuilder.header("Content-Length", Long.toString(contentLength));
requestBuilder.removeHeader("Transfer-Encoding");
} else {
requestBuilder.header("Transfer-Encoding", "chunked");
requestBuilder.removeHeader("Content-Length");
}
}
if (userRequest.header("Host") == null) {
requestBuilder.header("Host", hostHeader(userRequest.url(), false));
}
if (userRequest.header("Connection") == null) {
requestBuilder.header("Connection", "Keep-Alive");
}
// If we add an "Accept-Encoding: gzip" header field we're responsible for also decompressing
// the transfer stream.
boolean transparentGzip = false;
if (userRequest.header("Accept-Encoding") == null && userRequest.header("Range") == null) {
transparentGzip = true;
requestBuilder.header("Accept-Encoding", "gzip");
}
List<Cookie> cookies = cookieJar.loadForRequest(userRequest.url());
if (!cookies.isEmpty()) {
requestBuilder.header("Cookie", cookieHeader(cookies));
}
if (userRequest.header("User-Agent") == null) {
requestBuilder.header("User-Agent", Version.userAgent());
}
Response networkResponse = chain.proceed(requestBuilder.build());
HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());
Response.Builder responseBuilder = networkResponse.newBuilder()
.request(userRequest);
if (transparentGzip
&& "gzip".equalsIgnoreCase(networkResponse.header("Content-Encoding"))
&& HttpHeaders.hasBody(networkResponse)) {
GzipSource responseBody = new GzipSource(networkResponse.body().source());
Headers strippedHeaders = networkResponse.headers().newBuilder()
.removeAll("Content-Encoding")
.removeAll("Content-Length")
.build();
responseBuilder.headers(strippedHeaders);
String contentType = networkResponse.header("Content-Type");
responseBuilder.body(new RealResponseBody(contentType, -1L, Okio.buffer(responseBody)));
}
return responseBuilder.build();
}
CacheInterceptor 缓存拦截器
缓存的作用大家都理解就是当我们发出请求时，当符合条件，缓存中又恰好存在，则可以直接返回。看看CacheInterceptor中是如何实现的。首先我们会获得cacheCandidate和根据缓存策略得出的networkRequest ，cacheResponse 。所谓的策略就是缓存是否过期，利用etag，Expires。在if (cacheCandidate != null && cacheResponse == null)的情况下（缓存存在，但是根据缓存策略不能被使用），我们就close。在if (networkRequest == null && cacheResponse == null)情况下（网络请求不能被使用并且不存在可使用的缓存），就直接返回504的response。在if (networkRequest == null)情况下（不必网络请求），我们根据缓存策略得到的cacheResponse符合要求直接返回。
调用networkResponse = chain.proceed(networkRequest)，得到网络请求的结果。在if (networkResponse == null && cacheCandidate != null)的情况下（网络请求失败，没有获得响应包），直接close。在if (networkResponse.code() == HTTP_NOT_MODIFIED) （返回304），说明服务器数据没有变，可以使用缓存数据cacheResponse，同时更新一下cache。剩下的情况就是使用networkResponse的数据，并根据要求更新缓存。
@Override public Response intercept(Chain chain) throws IOException {
Response cacheCandidate = cache != null
? cache.get(chain.request())
: null;
long now = System.currentTimeMillis();
CacheStrategy strategy = new CacheStrategy.Factory(now, chain.request(), cacheCandidate).get();
Request networkRequest = strategy.networkRequest;
Response cacheResponse = strategy.cacheResponse;
if (cache != null) {
cache.trackResponse(strategy);
}
if (cacheCandidate != null && cacheResponse == null) {
closeQuietly(cacheCandidate.body()); // The cache candidate wasn't applicable. Close it.
}
// If we're forbidden from using the network and the cache is insufficient, fail.
if (networkRequest == null && cacheResponse == null) {
return new Response.Builder()
.request(chain.request())
.protocol(Protocol.HTTP_1_1)
.code(504)
.message("Unsatisfiable Request (only-if-cached)")
.body(Util.EMPTY_RESPONSE)
.sentRequestAtMillis(-1L)
.receivedResponseAtMillis(System.currentTimeMillis())
.build();
}
// If we don't need the network, we're done.
if (networkRequest == null) {
return cacheResponse.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.build();
}
Response networkResponse = null;
try {
networkResponse = chain.proceed(networkRequest);
} finally {
// If we're crashing on I/O or otherwise, don't leak the cache body.
if (networkResponse == null && cacheCandidate != null) {
closeQuietly(cacheCandidate.body());
}
}
// If we have a cache response too, then we're doing a conditional get.
if (cacheResponse != null) {
if (networkResponse.code() == HTTP_NOT_MODIFIED) {
Response response = cacheResponse.newBuilder()
.headers(combine(cacheResponse.headers(), networkResponse.headers()))
.sentRequestAtMillis(networkResponse.sentRequestAtMillis())
.receivedResponseAtMillis(networkResponse.receivedResponseAtMillis())
.cacheResponse(stripBody(cacheResponse))
.networkResponse(stripBody(networkResponse))
.build();
networkResponse.body().close();
// Update the cache after combining headers but before stripping the
// Content-Encoding header (as performed by initContentStream()).
cache.trackConditionalCacheHit();
cache.update(cacheResponse, response);
return response;
} else {
closeQuietly(cacheResponse.body());
}
}
Response response = networkResponse.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.networkResponse(stripBody(networkResponse))
.build();
if (cache != null) {
if (HttpHeaders.hasBody(response) && CacheStrategy.isCacheable(response, networkRequest)) {
// Offer this request to the cache.
CacheRequest cacheRequest = cache.put(response);
return cacheWritingResponse(cacheRequest, response);
}
if (HttpMethod.invalidatesCache(networkRequest.method())) {
try {
cache.remove(networkRequest);
} catch (IOException ignored) {
// The cache cannot be written.
}
}
}
return response;
}
ConnectInterceptor 网络连接
ConnectInterceptor主要就是TCP的连接，在streamAllocation.connection()中会调用RealConnection.connection()。当中我们就能看到包括tcp的连接，以及带上ssl的tcp连接。
@Override public Response intercept(Chain chain) throws IOException {
RealInterceptorChain realChain = (RealInterceptorChain) chain;
Request request = realChain.request();
StreamAllocation streamAllocation = realChain.streamAllocation();
// We need the network to satisfy this request. Possibly for validating a conditional GET.
boolean doExtensiveHealthChecks = !request.method().equals("GET");
HttpCodec httpCodec = streamAllocation.newStream(client, chain, doExtensiveHealthChecks);
RealConnection connection = streamAllocation.connection();
return realChain.proceed(request, streamAllocation, httpCodec, connection);
}
client.networkInterceptors()
开发者通过使用addNetworkInterceptor(Interceptor)设置，在这个位置可以看到每个请求和响应的数据。
OkHttpClient okHttpClient = new OkHttpClient.Builder()
.addNetworkInterceptor(new Interceptor() {
@Override
public Response intercept(Chain chain) throws IOException {
//获取一些未解码的内容
return null;
}
})
.build();
CallServerInterceptor
没有proceed，因为这是最后一环，不需要交给下一个拦截器。真正实际的请求与响应的I/O操作，向socket中写数据以及从socket中读数据。用的是okio的内容。
@Override public Response intercept(Chain chain) throws IOException {
RealInterceptorChain realChain = (RealInterceptorChain) chain;
HttpCodec httpCodec = realChain.httpStream();
StreamAllocation streamAllocation = realChain.streamAllocation();
RealConnection connection = (RealConnection) realChain.connection();
Request request = realChain.request();
long sentRequestMillis = System.currentTimeMillis();
realChain.eventListener().requestHeadersStart(realChain.call());
httpCodec.writeRequestHeaders(request);
realChain.eventListener().requestHeadersEnd(realChain.call(), request);
Response.Builder responseBuilder = null;
if (HttpMethod.permitsRequestBody(request.method()) && request.body() != null) {
// If there's a "Expect: 100-continue" header on the request, wait for a "HTTP/1.1 100
// Continue" response before transmitting the request body. If we don't get that, return
// what we did get (such as a 4xx response) without ever transmitting the request body.
if ("100-continue".equalsIgnoreCase(request.header("Expect"))) {
httpCodec.flushRequest();
realChain.eventListener().responseHeadersStart(realChain.call());
responseBuilder = httpCodec.readResponseHeaders(true);
}
if (responseBuilder == null) {
// Write the request body if the "Expect: 100-continue" expectation was met.
realChain.eventListener().requestBodyStart(realChain.call());
long contentLength = request.body().contentLength();
CountingSink requestBodyOut =
new CountingSink(httpCodec.createRequestBody(request, contentLength));
BufferedSink bufferedRequestBody = Okio.buffer(requestBodyOut);
request.body().writeTo(bufferedRequestBody);
bufferedRequestBody.close();
realChain.eventListener()
.requestBodyEnd(realChain.call(), requestBodyOut.successfulCount);
} else if (!connection.isMultiplexed()) {
// If the "Expect: 100-continue" expectation wasn't met, prevent the HTTP/1 connection
// from being reused. Otherwise we're still obligated to transmit the request body to
// leave the connection in a consistent state.
streamAllocation.noNewStreams();
}
}
httpCodec.finishRequest();
if (responseBuilder == null) {
realChain.eventListener().responseHeadersStart(realChain.call());
responseBuilder = httpCodec.readResponseHeaders(false);
}
Response response = responseBuilder
.request(request)
.handshake(streamAllocation.connection().handshake())
.sentRequestAtMillis(sentRequestMillis)
.receivedResponseAtMillis(System.currentTimeMillis())
.build();
int code = response.code();
if (code == 100) {
// server sent a 100-continue even though we did not request one.
// try again to read the actual response
responseBuilder = httpCodec.readResponseHeaders(false);
response = responseBuilder
.request(request)
.handshake(streamAllocation.connection().handshake())
.sentRequestAtMillis(sentRequestMillis)
.receivedResponseAtMillis(System.currentTimeMillis())
.build();
code = response.code();
}
realChain.eventListener()
.responseHeadersEnd(realChain.call(), response);
if (forWebSocket && code == 101) {
// Connection is upgrading, but we need to ensure interceptors see a non-null response body.
response = response.newBuilder()
.body(Util.EMPTY_RESPONSE)
.build();
} else {
response = response.newBuilder()
.body(httpCodec.openResponseBody(response))
.build();
}
if ("close".equalsIgnoreCase(response.request().header("Connection"))
|| "close".equalsIgnoreCase(response.header("Connection"))) {
streamAllocation.noNewStreams();
}
if ((code == 204 || code == 205) && response.body().contentLength() > 0) {
throw new ProtocolException(
"HTTP " + code + " had non-zero Content-Length: " + response.body().contentLength());
}
return response;
}
图示整个请求流程
下图是盗用的，哈哈哈。
简述请求过程.png
