摘要:昨天分析okhttp的请求流程,今天来分析下这几个拦截器

各种拦截器

RetryAndFollowUpInterceptor

直接上代码

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@Override public Response intercept(Chain chain) throws IOException {
Request request = chain.request();
//初始化连接对象
streamAllocation = new StreamAllocation(
client.connectionPool(), createAddress(request.url()));
int followUpCount = 0;
Response priorResponse = null;
while (true) {
if (canceled) {
streamAllocation.release();
throw new IOException("Canceled");
}
Response response = null;
boolean releaseConnection = true;
try {
//继续下一个拦截器
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.
if (!recover(e.getLastConnectException(), true, request)) throw e.getLastConnectException();
releaseConnection = false;
continue;
} catch (IOException e) {
// An attempt to communicate with a server failed. The request may have been sent.
if (!recover(e, false, 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);
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) {
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()));
} else if (streamAllocation.stream() != null) {
throw new IllegalStateException("Closing the body of " + response
+ " didn't close its backing stream. Bad interceptor?");
}
request = followUp;
priorResponse = response;
}
}

实例化StreamAllocation,初始化一个Socket连接对象,获取到输入/输出流()基于Okio
开启循环,执行下一个调用链(拦截器),等待返回结果(Response)
如果发生错误,判断是否继续请求,否:退出
检查响应是否符合要求,是:返回
关闭响应结果
判断是否达到最大限制数,是:退出
检查是否有相同连接,是:释放,重建连接
重复以上流程

BridgeInterceptor

本拦截器的主要功能是:处理请求头(header),将自定义的头和协议必须的头合在一起,如果有自定义使用自定义的,没有就生成默认头

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@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) {
transparentGzip = true;
requestBuilder.header("Accept-Encoding", "gzip");
}
// 创建Okhpptclitent时候配置的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());
}
// 以上为请求前的头处理 下面是调用接下来的拦截器
Response networkResponse = chain.proceed(requestBuilder.build());
// 以下是请求完成,拿到返回后的头处理
HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());
Response.Builder responseBuilder = networkResponse.newBuilder()
.request(userRequest);
//前面解析完header后,判断服务器是否支持gzip压缩格式,如果支持将交给Okio处理
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();
}

CacheInterceptor

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@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(EMPTY_BODY)
.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 (validate(cacheResponse, networkResponse)) {
Response response = cacheResponse.newBuilder()
.headers(combine(cacheResponse.headers(), networkResponse.headers()))
.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 (HttpHeaders.hasBody(response)) {
CacheRequest cacheRequest = maybeCache(response, networkResponse.request(), cache);
response = cacheWritingResponse(cacheRequest, response);
}
return response;
}

就是先走自己的缓存策略,如果又缓存就直接返回了 Response,如果没有就进入下个拦截器

ConnectInterceptor

倒数第二个拦截器—连接拦截器,这才是真正的开始向服务端发起进攻

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package okhttp3.internal.connection;
import java.io.IOException;
import okhttp3.Interceptor;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.internal.http.HttpStream;
import okhttp3.internal.http.RealInterceptorChain;
/** Opens a connection to the target server and proceeds to the next interceptor. */
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");
//实例化httpcodec,如果是http2.0实例化Http1Stream否则Http2Stream
HttpStream httpStream = streamAllocation.newStream(client, doExtensiveHealthChecks);
RealConnection connection = streamAllocation.connection();
return realChain.proceed(request, streamAllocation, httpStream, connection);
}
}

对没错 就这么几行代码,处的逻辑很简单,因为已经转嫁到其他的类对象上去了。前面我们提到过RealInterceptorChain构造函数有四个重要的属性(Request、StreamAllocation, HttpStream、Connection)第一个不用说一开始就必须有,第二个是在重试拦截器中实例化的,第三、第四就是在本节中腰实例化出来的。StreamAllocation 我们知道是在第一个拦截器创建。

newStream

深入看一下 newStream 方法

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public HttpStream newStream(OkHttpClient client, boolean doExtensiveHealthChecks) {
int connectTimeout = client.connectTimeoutMillis();
int readTimeout = client.readTimeoutMillis();
int writeTimeout = client.writeTimeoutMillis();
boolean connectionRetryEnabled = client.retryOnConnectionFailure();
try {
//判断之前是否又连接
RealConnection resultConnection = findHealthyConnection(connectTimeout, readTimeout,
writeTimeout, connectionRetryEnabled, doExtensiveHealthChecks);
HttpStream resultStream;
if (resultConnection.framedConnection != null) {
resultStream = new Http2xStream(client, this, resultConnection.framedConnection);
} else {
resultConnection.socket().setSoTimeout(readTimeout);
resultConnection.source.timeout().timeout(readTimeout, MILLISECONDS);
resultConnection.sink.timeout().timeout(writeTimeout, MILLISECONDS);
resultStream = new Http1xStream(
client, this, resultConnection.source, resultConnection.sink);
}
synchronized (connectionPool) {
stream = resultStream;
return resultStream;
}
} catch (IOException e) {
throw new RouteException(e);
}
}

这里就是获取连接 根据framedConnection 创建 HttpStream

framedConnection

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private RealConnection findHealthyConnection(int connectTimeout, int readTimeout,
int writeTimeout, boolean connectionRetryEnabled, boolean doExtensiveHealthChecks)
throws IOException {
while (true) {
RealConnection candidate = findConnection(connectTimeout, readTimeout, writeTimeout,
connectionRetryEnabled);
// If this is a brand new connection, we can skip the extensive health checks.
synchronized (connectionPool) {
if (candidate.successCount == 0) {
return candidate;
}
}
// Do a (potentially slow) check to confirm that the pooled connection is still good. If it
// isn't, take it out of the pool and start again.
if (!candidate.isHealthy(doExtensiveHealthChecks)) {
noNewStreams();
continue;
}
return candidate;
}
}

看findConnection 方法

findConnection

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private RealConnection findConnection(int connectTimeout, int readTimeout, int writeTimeout,
boolean connectionRetryEnabled) throws IOException {
Route selectedRoute;
synchronized (connectionPool) {
if (released) throw new IllegalStateException("released");
if (stream != null) throw new IllegalStateException("stream != null");
if (canceled) throw new IOException("Canceled");
// 使用已存在的连接
RealConnection allocatedConnection = this.connection;
if (allocatedConnection != null && !allocatedConnection.noNewStreams) {
return allocatedConnection;
}
//从连接池里获取
// Attempt to get a connection from the pool.
RealConnection pooledConnection = Internal.instance.get(connectionPool, address, this);
if (pooledConnection != null) {
this.connection = pooledConnection;
return pooledConnection;
}
selectedRoute = route;
}
if (selectedRoute == null) {
selectedRoute = routeSelector.next();
synchronized (connectionPool) {
route = selectedRoute;
refusedStreamCount = 0;
}
}
//以上都不符合,创建一个连接
RealConnection newConnection = new RealConnection(selectedRoute);
acquire(newConnection);
synchronized (connectionPool) {
//放入线程池
Internal.instance.put(connectionPool, newConnection);
this.connection = newConnection;
if (canceled) throw new IOException("Canceled");
}
newConnection.connect(connectTimeout, readTimeout, writeTimeout, address.connectionSpecs(),
connectionRetryEnabled);
routeDatabase().connected(newConnection.route());
return newConnection;
}

connect

建立一个新连接

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public void connect(int connectTimeout, int readTimeout, int writeTimeout,
List<ConnectionSpec> connectionSpecs, boolean connectionRetryEnabled) {
if (protocol != null) throw new IllegalStateException("already connected");
RouteException routeException = null;
ConnectionSpecSelector connectionSpecSelector = new ConnectionSpecSelector(connectionSpecs);
if (route.address().sslSocketFactory() == null) {
if (!connectionSpecs.contains(ConnectionSpec.CLEARTEXT)) {
throw new RouteException(new UnknownServiceException(
"CLEARTEXT communication not enabled for client"));
}
String host = route.address().url().host();
if (!Platform.get().isCleartextTrafficPermitted(host)) {
throw new RouteException(new UnknownServiceException(
"CLEARTEXT communication to " + host + " not permitted by network security policy"));
}
}
//开始连接
while (protocol == null) {
try {
if (route.requiresTunnel()) {
// 如果要求通道模式,建立通道连接,通常不是这种
buildTunneledConnection(connectTimeout, readTimeout, writeTimeout,
connectionSpecSelector);
} else {
// 一般都走这条逻辑了,实际上很简单就是socket的连接
buildConnection(connectTimeout, readTimeout, writeTimeout, connectionSpecSelector);
}
} catch (IOException e) {
closeQuietly(socket);
closeQuietly(rawSocket);
socket = null;
rawSocket = null;
source = null;
sink = null;
handshake = null;
protocol = null;
if (routeException == null) {
routeException = new RouteException(e);
} else {
routeException.addConnectException(e);
}
if (!connectionRetryEnabled || !connectionSpecSelector.connectionFailed(e)) {
throw routeException;
}
}
}
}

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private void buildConnection(int connectTimeout, int readTimeout, int writeTimeout,
ConnectionSpecSelector connectionSpecSelector) throws IOException {
//建立连接
connectSocket(connectTimeout, readTimeout);
//简历协议
establishProtocol(readTimeout, writeTimeout, connectionSpecSelector);
}

对于这两个方法 咱们一个一个看

connectSocket

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private void connectSocket(int connectTimeout, int readTimeout) throws IOException {
Proxy proxy = route.proxy();
Address address = route.address();
rawSocket = proxy.type() == Proxy.Type.DIRECT || proxy.type() == Proxy.Type.HTTP
? address.socketFactory().createSocket()
: new Socket(proxy);
rawSocket.setSoTimeout(readTimeout);
try {
//连接Socket
Platform.get().connectSocket(rawSocket, route.socketAddress(), connectTimeout);
} catch (ConnectException e) {
throw new ConnectException("Failed to connect to " + route.socketAddress());
}
//得到 输入流 和输出流
source = Okio.buffer(Okio.source(rawSocket));
sink = Okio.buffer(Okio.sink(rawSocket));
}

connectSocket 方法简历了连接,得到了一个输入流和输出流,当然 可以看到 关于流这里 交给了okio来处理,关于okio 以后在说

establishProtocol

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private void establishProtocol(int readTimeout, int writeTimeout,
ConnectionSpecSelector connectionSpecSelector) throws IOException {
//判断是不是 https 如果是 就在上面在套一层
if (route.address().sslSocketFactory() != null) {
connectTls(readTimeout, writeTimeout, connectionSpecSelector);
} else {
protocol = Protocol.HTTP_1_1;
socket = rawSocket;
}
if (protocol == Protocol.SPDY_3 || protocol == Protocol.HTTP_2) {
socket.setSoTimeout(0); // Framed connection timeouts are set per-stream.
FramedConnection framedConnection = new FramedConnection.Builder(true)
.socket(socket, route.address().url().host(), source, sink)
.protocol(protocol)
.listener(this)
.build();
framedConnection.start();
// Only assign the framed connection once the preface has been sent successfully.
this.allocationLimit = framedConnection.maxConcurrentStreams();
this.framedConnection = framedConnection;
} else {
this.allocationLimit = 1;
}
}

CallServerInterceptor

到了 就是最后一个拦截器,这里包括了 发送请求,和返回最终的 response

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@Override public Response intercept(Chain chain) throws IOException {
HttpStream httpStream = ((RealInterceptorChain) chain).httpStream();
StreamAllocation streamAllocation = ((RealInterceptorChain) chain).streamAllocation();
Request request = chain.request();
long sentRequestMillis = System.currentTimeMillis();
//写入http 头,两个httpStream具体实现不一样 不过都交给 okio来处理
httpStream.writeRequestHeaders(request);
if (HttpMethod.permitsRequestBody(request.method()) && request.body() != null) {
Sink requestBodyOut = httpStream.createRequestBody(request, request.body().contentLength());
BufferedSink bufferedRequestBody = Okio.buffer(requestBodyOut);
request.body().writeTo(bufferedRequestBody);
bufferedRequestBody.close();
}
//完成请求
httpStream.finishRequest();
//读取响应头
Response response = httpStream.readResponseHeaders()
.request(request)
.handshake(streamAllocation.connection().handshake())
.sentRequestAtMillis(sentRequestMillis)
.receivedResponseAtMillis(System.currentTimeMillis())
.build();
//读取响应body
if (!forWebSocket || response.code() != 101) {
response = response.newBuilder()
.body(httpStream.openResponseBody(response))
.build();
}
if ("close".equalsIgnoreCase(response.request().header("Connection"))
|| "close".equalsIgnoreCase(response.header("Connection"))) {
streamAllocation.noNewStreams();
}
int code = response.code();
if ((code == 204 || code == 205) && response.body().contentLength() > 0) {
throw new ProtocolException(
"HTTP " + code + " had non-zero Content-Length: " + response.body().contentLength());
}
return response;
}

这里就是先获取上个拦截器的连接,然后 获取到 上个拦截器的httpStream 里面不又生成的那些流吗,然后写入头,写入请求体,在读取头 读取体

###好了,对于OKhttp就先分析这些了,写的像流水账一样