书接前文，同步和异步请求均调用了同一个方法getResponseWithInterceptorChain()那么此方法做了什么事情？
getResponseWithInterceptorChain()
Response getResponseWithInterceptorChain() throws IOException {
// Build a full stack of interceptors.
List<Interceptor> interceptors = new ArrayList<>();
//添加开发者应用层自定义的Interceptor
interceptors.addAll(client.interceptors());
//这个Interceptor是处理请求失败的重试，重定向
interceptors.add(retryAndFollowUpInterceptor);
//这个Interceptor工作是添加一些请求的头部或其他信息
//并对返回的Response做一些友好的处理（有一些信息你可能并不需要）
interceptors.add(new BridgeInterceptor(client.cookieJar()));
//这个Interceptor的职责是判断缓存是否存在，读取缓存，更新缓存等等
interceptors.add(new CacheInterceptor(client.internalCache()));
//这个Interceptor的职责是建立客户端和服务器的连接
interceptors.add(new ConnectInterceptor(client));
if (!forWebSocket) {
//添加开发者自定义的网络层拦截器
interceptors.addAll(client.networkInterceptors());
}
interceptors.add(new CallServerInterceptor(forWebSocket));
//一个包裹这request的chain
Interceptor.Chain chain = new RealInterceptorChain(
interceptors, null, null, null, 0, originalRequest);
//把chain传递到第一个Interceptor手中
return chain.proceed(originalRequest);
}这就很有意思了，我输入一个List<Interceptor>的集合，你只返回给我Response一个对象，经过层层的list内的Interceptor拦击之后最后也是也组装成一个Response返回。所以看来我们需要先看一下Interceptor这个大父类
Interceptor
现在让我们从Interceptor接口开始一点一点看
public interface Interceptor {
Response intercept(Chain chain) throws IOException;
interface Chain {
Request request();
//分发处理
Response proceed(Request request) throws IOException;
Connection connection();
}
}可以看到接口Chain才是真正的拦截发生者的主要父类接口，那么其具体实这里先列举一下所有的拦截器，本文挨个排着解析一遍
- RetryAndFollowUpInterceptor
这拦截器主要是做重试，网络错误，以及请求重定向的一些操作。 - BridgeInterceptor
这个拦截器，主要把用户的请求转换为网络的请求，负责对Request和Response报文进行加工。 - CacheInterceptor
缓存拦截器 - ConnectInterceptor
连接拦截器，主要是处理连接服务器，以及http , https的包装 - CallServerInterceptor
服务拦截器，主要是发送（write、input）、读取（read、output）数据。也是拦截器的最后一个环节，这里就真正拿到了网络的结果了。
这里有个问题，这么多的子类是如何配合进而完成了okhttp的拦截功能？答案就是RealInterceptorChain其实现的经典的责任链模式通过层层拦截进而完成组装。先看一下源码
责任链
首先我要抽出必要的代码来讲解一下okhttp的责任链模式；
RealCall
RealCall(OkHttpClient client, Request originalRequest, boolean forWebSocket) {
final EventListener.Factory eventListenerFactory = client.eventListenerFactory();
this.client = client;
this.originalRequest = originalRequest;
this.forWebSocket = forWebSocket;
this.retryAndFollowUpInterceptor = new RetryAndFollowUpInterceptor(client, forWebSocket);
// TODO(jwilson): this is unsafe publication and not threadsafe.
this.eventListener = eventListenerFactory.create(this);
}
Response getResponseWithInterceptorChain() throws IOException {
//省略
Interceptor.Chain chain = new RealInterceptorChain(
interceptors, null, null, null, 0, originalRequest);
return chain.proceed(originalRequest);
}我们可以发现RealCall通过getResponseWithInterceptorChain通过了new RealInterceptorChain(interceptors, null, null, null, 0, originalRequest)的方式实现了拦截器的第一次初始化操作
RealInterceptorChain
public RealInterceptorChain(List<Interceptor> interceptors, StreamAllocation streamAllocation,
HttpCodec httpCodec, RealConnection connection, int index, Request request) {
this.interceptors = interceptors;
this.connection = connection;
this.streamAllocation = streamAllocation;
this.httpCodec = httpCodec;
this.index = index;
this.request = request;
}
//注意这个多态方法
@Override public Response proceed(Request request) throws IOException {
return proceed(request, streamAllocation, httpCodec, connection);
}
public Response proceed(Request request, StreamAllocation streamAllocation, HttpCodec httpCodec, RealConnection connection) throws IOException {
//忽略部分代码
// Call the next interceptor in the chain.
RealInterceptorChain next = new RealInterceptorChain(
interceptors, streamAllocation, httpCodec, connection, index + 1, request);
Interceptor interceptor = interceptors.get(index);
Response response = interceptor.intercept(next);
//忽略部分代码
}
return response;
}重头戏！该类本事通过不停的调用自己的构造器（new RealInterceptorChain）的方式实现了每次index自增，interceptors.get(index);也就实现了链式调用排好的构造器，通过每次调用子类的intercept()方法实现调取不同子类。那么你子类又是怎么回传给父类的？这里一定要注意proceed(Request request)和proceed(Request request, StreamAllocation streamAllocation, HttpCodec httpCodec, RealConnection connection)这两个多态方法！
因为不同的拦截器会回调不同的方法。我们也就可以知道不同的参数在不同的拦截器中得到了初始化。
RetryAndFollowUpInterceptor
@Override public Response intercept(Chain chain) throws IOException {
//忽略部分代码
response = ((RealInterceptorChain) chain).proceed(request, streamAllocation, null, null);//回调RealInterceptorChain的proceed方法！注意此地的参数是四个值，streamAllocation在此地被赋值
//忽略部分代码
}BridgeInterceptor
@Override public Response intercept(Chain chain) throws IOException {
//忽略部分代码
Response networkResponse = chain.proceed(requestBuilder.build());
注意此地RealInterceptorChain的proceed方法！注意此地的参数是一个，
//回调RealInterceptorChain的proceed方法
//忽略部分代码
}CacheInterceptor
@Override public Response intercept(Chain chain) throws IOException {
//忽略部分代码
networkResponse = chain.proceed(networkRequest);
注意此地RealInterceptorChain的proceed方法！注意此地的参数是一个
//忽略部分代码
}ConnectInterceptor
@Override public Response intercept(Chain chain) throws IOException {
//忽略部分代码
return realChain.proceed(request, streamAllocation, httpCodec, connection);
注意此地RealInterceptorChain的proceed方法！注意此地的参数是四个，httpCodec, connection在此得到赋值。
}CallServerInterceptor
@Override public Response intercept(Chain chain) throws IOException {
//忽略部分代码
return response;
}可以看到CallServerInterceptor之前的连接器均调用了相关的realChain.proceed方法进行了一个链式的组装。到现在责任链的模式讲完了，接下来看看具体的每一个Interceptor干了什么
RetryAndFollowUpInterceptor
public final class RetryAndFollowUpInterceptor implements Interceptor {
/**
* How many redirects and auth challenges should we attempt? Chrome follows 21 redirects; Firefox,
* curl, and wget follow 20; Safari follows 16; and HTTP/1.0 recommends 5.
*/
//最大恢复追逐次数：
private static final int MAX_FOLLOW_UPS = 20;
private final OkHttpClient client;
private final boolean forWebSocket;
private StreamAllocation streamAllocation;
private Object callStackTrace;
private volatile boolean canceled;
public RetryAndFollowUpInterceptor(OkHttpClient client, boolean forWebSocket) {
this.client = client;
this.forWebSocket = forWebSocket;
}
/**
* Immediately closes the socket connection if it's currently held. Use this to interrupt an
* in-flight request from any thread. It's the caller's responsibility to close the request body
* and response body streams; otherwise resources may be leaked.
*
* <p>This method is safe to be called concurrently, but provides limited guarantees. If a
* transport layer connection has been established (such as a HTTP/2 stream) that is terminated.
* Otherwise if a socket connection is being established, that is terminated.
*/
public void cancel() {
canceled = true;
StreamAllocation streamAllocation = this.streamAllocation;
if (streamAllocation != null) streamAllocation.cancel();
}
public boolean isCanceled() {
return canceled;
}
public void setCallStackTrace(Object callStackTrace) {
this.callStackTrace = callStackTrace;
}
public StreamAllocation streamAllocation() {
return streamAllocation;
}
@Override public Response intercept(Chain chain) throws IOException {
Request request = chain.request();
streamAllocation = new StreamAllocation(
// 三个参数分别对应：(1)全局的连接池，(2)连接线路Address, (3)堆栈对象
client.connectionPool(), createAddress(request.url()), callStackTrace);
int followUpCount = 0;
Response priorResponse = null;
while (true) {
if (canceled) {
streamAllocation.release();
throw new IOException("Canceled");
}
Response response = null;
boolean releaseConnection = true;
try {
// 执行下一个拦截器，即BridgeInterceptor
// RealInterceptorChain会将初始化好的连接对象传递给下一个拦截器，也是贯穿整个请求的对象，在拦截器执行过程中，的几个属性字段会一步一步赋值
response = ((RealInterceptorChain) chain).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.
// 如果有异常，判断是否要恢复
if (!recover(e.getLastConnectException(), 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, 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();
}
// 检查是否符合要求
Request followUp = followUpRequest(response);
if (followUp == null) {
if (!forWebSocket) {
streamAllocation.release();
}
// 返回结果
return response;
}
//不符合，关闭响应流
closeQuietly(response.body());
// 是否超过最大限制
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());
}
// 是否有相同的连接
if (!sameConnection(response, followUp.url())) {
streamAllocation.release();
streamAllocation = new StreamAllocation(
client.connectionPool(), createAddress(followUp.url()), callStackTrace);
} 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;
}
}
private Address createAddress(HttpUrl url) {
SSLSocketFactory sslSocketFactory = null;
HostnameVerifier hostnameVerifier = null;
CertificatePinner certificatePinner = null;
if (url.isHttps()) {
sslSocketFactory = client.sslSocketFactory();
hostnameVerifier = client.hostnameVerifier();
certificatePinner = client.certificatePinner();
}
return new Address(url.host(), url.port(), client.dns(), client.socketFactory(),
sslSocketFactory, hostnameVerifier, certificatePinner, client.proxyAuthenticator(),
client.proxy(), client.protocols(), client.connectionSpecs(), client.proxySelector());
}
/**
* Report and attempt to recover from a failure to communicate with a server. Returns true if
* {@code e} is recoverable, or false if the failure is permanent. Requests with a body can only
* be recovered if the body is buffered or if the failure occurred before the request has been
* sent.
*/
private boolean recover(IOException e, boolean requestSendStarted, Request userRequest) {
streamAllocation.streamFailed(e);
// 1. 应用层配置不在连接，默认为true
// The application layer has forbidden retries.
if (!client.retryOnConnectionFailure()) return false;
// 2. 请求Request出错不能继续使用
// We can't send the request body again.
if (requestSendStarted && userRequest.body() instanceof UnrepeatableRequestBody) return false;
// 是否可以恢复的
// This exception is fatal.
if (!isRecoverable(e, requestSendStarted)) return false;
// 4. 没用更多线路可供选择
// No more routes to attempt.
if (!streamAllocation.hasMoreRoutes()) return false;
// For failure recovery, use the same route selector with a new connection.
return true;
}
1.应用层配置不在连接(默认为true)，则不可恢复
2.请求Request是不可重复使用的Request，则不可恢复
3.根据Exception的类型判断是否可以恢复的 (isRecoverable()方法)
3.1、如果是协议错误（ProtocolException）则不可恢复
3.2、如果是中断异常（InterruptedIOException）则不可恢复
3.3、如果是SSL握手错误（SSLHandshakeException && CertificateException）则不可恢复
3.4、certificate pinning错误（SSLPeerUnverifiedException）则不可恢复
4.没用更多线路可供选择 则不可恢复
如果上述条件都不满足，则这个request可以恢复
private boolean isRecoverable(IOException e, boolean requestSendStarted) {
// If there was a protocol problem, don't recover.
if (e instanceof ProtocolException) {
return false;
}
// If there was an interruption don't recover, but if there was a timeout connecting to a route
// we should try the next route (if there is one).
if (e instanceof InterruptedIOException) {
return e instanceof SocketTimeoutException && !requestSendStarted;
}
// Look for known client-side or negotiation errors that are unlikely to be fixed by trying
// again with a different route.
if (e instanceof SSLHandshakeException) {
// If the problem was a CertificateException from the X509TrustManager,
// do not retry.
if (e.getCause() instanceof CertificateException) {
return false;
}
}
if (e instanceof SSLPeerUnverifiedException) {
// e.g. a certificate pinning error.
return false;
}
// An example of one we might want to retry with a different route is a problem connecting to a
// proxy and would manifest as a standard IOException. Unless it is one we know we should not
// retry, we return true and try a new route.
return true;
}
/**
* Figures out the HTTP request to make in response to receiving {@code userResponse}. This will
* either add authentication headers, follow redirects or handle a client request timeout. If a
* follow-up is either unnecessary or not applicable, this returns null.
*/
private Request followUpRequest(Response userResponse) throws IOException {
if (userResponse == null) throw new IllegalStateException();
Connection connection = streamAllocation.connection();
Route route = connection != null
? connection.route()
: null;
int responseCode = userResponse.code();
final String method = userResponse.request().method();
switch (responseCode) {
case HTTP_PROXY_AUTH:
Proxy selectedProxy = route != null
? route.proxy()
: client.proxy();
if (selectedProxy.type() != Proxy.Type.HTTP) {
throw new ProtocolException("Received HTTP_PROXY_AUTH (407) code while not using proxy");
}
return client.proxyAuthenticator().authenticate(route, userResponse);
case HTTP_UNAUTHORIZED:
return client.authenticator().authenticate(route, userResponse);
case HTTP_PERM_REDIRECT:
case HTTP_TEMP_REDIRECT:
// "If the 307 or 308 status code is received in response to a request other than GET
// or HEAD, the user agent MUST NOT automatically redirect the request"
if (!method.equals("GET") && !method.equals("HEAD")) {
return null;
}
// fall-through
case HTTP_MULT_CHOICE:
case HTTP_MOVED_PERM:
case HTTP_MOVED_TEMP:
case HTTP_SEE_OTHER:
// Does the client allow redirects?
if (!client.followRedirects()) return null;
String location = userResponse.header("Location");
if (location == null) return null;
HttpUrl url = userResponse.request().url().resolve(location);
// Don't follow redirects to unsupported protocols.
if (url == null) return null;
// If configured, don't follow redirects between SSL and non-SSL.
boolean sameScheme = url.scheme().equals(userResponse.request().url().scheme());
if (!sameScheme && !client.followSslRedirects()) return null;
// Most redirects don't include a request body.
Request.Builder requestBuilder = userResponse.request().newBuilder();
if (HttpMethod.permitsRequestBody(method)) {
final boolean maintainBody = HttpMethod.redirectsWithBody(method);
if (HttpMethod.redirectsToGet(method)) {
requestBuilder.method("GET", null);
} else {
RequestBody requestBody = maintainBody ? userResponse.request().body() : null;
requestBuilder.method(method, requestBody);
}
if (!maintainBody) {
requestBuilder.removeHeader("Transfer-Encoding");
requestBuilder.removeHeader("Content-Length");
requestBuilder.removeHeader("Content-Type");
}
}
// When redirecting across hosts, drop all authentication headers. This
// is potentially annoying to the application layer since they have no
// way to retain them.
if (!sameConnection(userResponse, url)) {
requestBuilder.removeHeader("Authorization");
}
return requestBuilder.url(url).build();
case HTTP_CLIENT_TIMEOUT:
// 408's are rare in practice, but some servers like HAProxy use this response code. The
// spec says that we may repeat the request without modifications. Modern browsers also
// repeat the request (even non-idempotent ones.)
if (userResponse.request().body() instanceof UnrepeatableRequestBody) {
return null;
}
return userResponse.request();
default:
return null;
}
}
/**
* Returns true if an HTTP request for {@code followUp} can reuse the connection used by this
* engine.
*/
private boolean sameConnection(Response response, HttpUrl followUp) {
HttpUrl url = response.request().url();
return url.host().equals(followUp.host())
&& url.port() == followUp.port()
&& url.scheme().equals(followUp.scheme());
}
}总结
- 根据url创建一个Address对象，初始化一个Socket连接对象，基于Okio
- 用前面创建的address作为参数去实例化StreamAllocation
PS：此处还没有真正的去建立连接，只是初始化一个连接对象 - 开启一个while(true)循环
- 如果取消，释放资源并抛出异常，结束流程
- 执行下一个拦截器，一般是BridgeInterceptor
- 如果发生异常，走到catch里面，判断是否继续请求，不继续请求则退出
- 如果priorResponse不为空，则说明前面已经获取到了响应，这里会结合当前获取的Response和先前的Response
- 调用followUpRequest查看响应是否需要重定向，如果不需要重定向则返回当前请求
- 重定向次数+1，同时判断是否达到最大限制数量。是：退出
- 检查是否有相同的链接，是：释放，重建创建
- 重新设置request，并把当前的Response保存到priorResponse，继续while循环
BridgeInterceptor
这个类主要完成了
- 从应用层数据类型类型到网络调用层的数据类型的转行，讲我们的javaBean搞进了报文的header内
-
cookie的处理
-
Gzip 转码
public final class BridgeInterceptor implements Interceptor {
private final CookieJar cookieJar;
public BridgeInterceptor(CookieJar cookieJar) {
this.cookieJar = cookieJar;
}
@Override public Response intercept(Chain chain) throws IOException {
Request userRequest = chain.request();
Request.Builder requestBuilder = userRequest.newBuilder();
//请求头部报文处理
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");
}
//如果我们不自定义编解码方式的方式，默认使用Gzip的编解码
// 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");
}
//在创建ohHttpClient的时候，添加的cookiejar。
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);
responseBuilder.body(new RealResponseBody(strippedHeaders, Okio.buffer(responseBody)));
}
return responseBuilder.build();
}
//从前面okHttpClient 中设置的cookieJar，然后设置到请求头的Cookie中去。
/** Returns a 'Cookie' HTTP request header with all cookies, like {@code a=b; c=d}. */
private String cookieHeader(List<Cookie> cookies) {
StringBuilder cookieHeader = new StringBuilder();
for (int i = 0, size = cookies.size(); i < size; i++) {
if (i > 0) {
cookieHeader.append("; ");
}
Cookie cookie = cookies.get(i);
cookieHeader.append(cookie.name()).append('=').append(cookie.value());
}
return cookieHeader.toString();
}
}CacheInterceptor
根据http报文内的CacheControl Cache等内容结合本地的缓存控制策略进行缓存处理
public final class CacheInterceptor implements Interceptor {
final InternalCache cache;
public CacheInterceptor(InternalCache cache) {
this.cache = cache;
}
@Override public Response intercept(Chain chain) throws IOException {
//1. 读取候选缓存；
Response cacheCandidate = cache != null
? cache.get(chain.request())
: null;
long now = System.currentTimeMillis();
//2. 创建缓存策略（强制缓存，对比缓存等策略)；
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.
//根据策略，不使用网络，缓存又没有直接报错；
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();
}
// 4. 根据策略，不使用网络，有缓存就直接返回；
// If we don't need the network, we're done.
if (networkRequest == null) {
return cacheResponse.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.build();
}
Response networkResponse = null;
try {
// 5. 前面个都没有返回，走下一个拦截器；
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());
}
}
//6. 接收到的网络结果，如果是code 304, 使用缓存，返回缓存结果（对比缓存）
// 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());
}
}
//7. 读取网络结果；
Response response = networkResponse.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.networkResponse(stripBody(networkResponse))
.build();
//8. 对数据进行缓存；
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
三次握手就在此处后文会详解，但是这个类的作用即为与后台建立连接完成通信前的准备工作
public final class ConnectInterceptor implements Interceptor {
public final OkHttpClient client;
public ConnectInterceptor(OkHttpClient client) {
this.client = client;
}
@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, doExtensiveHealthChecks);
RealConnection connection = streamAllocation.connection();
return realChain.proceed(request, streamAllocation, httpCodec, connection);
}
}CallServerInterceptor
连接搭建后进行真正的通信操作，利用okio进行流式的信息传递
public final class CallServerInterceptor implements Interceptor {
private final boolean forWebSocket;
public CallServerInterceptor(boolean forWebSocket) {
this.forWebSocket = forWebSocket;
}
@Override public Response intercept(Chain chain) throws IOException {
RealInterceptorChain realChain = (RealInterceptorChain) chain;
HttpCodec httpCodec = realChain.httpStream();
//HttpCodec用来读写数据
StreamAllocation streamAllocation = realChain.streamAllocation();
RealConnection connection = (RealConnection) realChain.connection();
Request request = realChain.request();
long sentRequestMillis = System.currentTimeMillis();
//写入请求头
httpCodec.writeRequestHeaders(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();
responseBuilder = httpCodec.readResponseHeaders(true);
}
//写入请求体
if (responseBuilder == null) {
// Write the request body if the "Expect: 100-continue" expectation was met.
Sink requestBodyOut = httpCodec.createRequestBody(request, request.body().contentLength());
BufferedSink bufferedRequestBody = Okio.buffer(requestBodyOut);
request.body().writeTo(bufferedRequestBody);
bufferedRequestBody.close();
} 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();
//读取响应头
if (responseBuilder == null) {
responseBuilder = httpCodec.readResponseHeaders(false);
}
Response response = responseBuilder
.request(request)
.handshake(streamAllocation.connection().handshake())
.sentRequestAtMillis(sentRequestMillis)
.receivedResponseAtMillis(System.currentTimeMillis())
.build();
//读取响应体
int code = response.code();
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;
}
}下一篇着重分析一下缓存处理和lru算法。
