使用
get
OkHttpClient client=new OkHttpClient();
Request request=new Request.Builder()
.url("www.baidu.com")
.build();
Call call=client.newCall(request);
Response response=call.execute();
ResponseBody responseBody=response.body();
post
OkHttpClient client=new OkHttpClient();
RequestBody requestBody=new FormBody.Builder().add("li","bo")
.build();
Request request=new Request.Builder()
.url("www.baidu.com")
.post(requestBody)
.build();
Call call=client.newCall(request);
Response response=call.execute();
ResponseBody responseBody=response.body();
调用流程
请求在执行前，先通过分发器再通过拦截器，最终执行的最后的操作
- 分发器的作用：内部维护队列和线程池，来完成请求调配
- 拦截器 五大拦截器进行钩子拦截 最终完成请求过程
分发器
异步请求
- 根据当前的线程池的空闲数量来执行等待和立即执行
synchronized void enqueue(AsyncCall call) {
//todo : 1、如果正在执行的请求小于64
// 2、相同host的请求不能超过5个
if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) {
runningAsyncCalls.add(call); //正在执行的请求
executorService().execute(call); //线程池跑任务
} else {
readyAsyncCalls.add(call);
}
}
- 当运行数小于最大值，并且有等待执行的任务。检测遍历readyAsyncCalls。加入到runningAsyncCalls 并执行
private void promoteCalls() {
if (runningAsyncCalls.size() >= maxRequests) return; // Already running max capacity.
if (readyAsyncCalls.isEmpty()) return; // No ready calls to promote.
for (Iterator<AsyncCall> i = readyAsyncCalls.iterator(); i.hasNext(); ) {
AsyncCall call = i.next();
// 同一Host请求只能同时有5个
if (runningCallsForHost(call) < maxRequestsPerHost) {
i.remove();
runningAsyncCalls.add(call);
executorService().execute(call);
}
if (runningAsyncCalls.size() >= maxRequests) return; // Reached max capacity.
}
}
同步请求
立即执行，只判断IdleRunnable 是否执行
线程池
在runningAsyncCalls 线程池执行，无等待，最大程度并发
拦截器
在call 执行请求执行了拦截器 getResponseWithInterceptorChain() 获取请求的结果
Response getResponseWithInterceptorChain() throws IOException {
// Build a full stack of interceptors.
List<Interceptor> interceptors = new ArrayList<>();
interceptors.addAll(client.interceptors()); //自定义拦截器加入到集合
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);
}
}
retryAndFollowUpInterceptor
重试拦截器: 判断用户是否取消请求，在获得结果后，会根据响应码判断是否需要重定向，如果满足条件会重新启动所有的拦截器
public Response intercept(Chain chain) throws IOException {
Request request = chain.request();
RealInterceptorChain realChain = (RealInterceptorChain) chain;
Call call = realChain.call();
EventListener eventListener = realChain.eventListener();
/**
* todo 管理类，维护了 与服务器的连接、数据流与请求三者的关系。真正使用的拦截器为 Connect
*/
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 {
//todo 请求出现了异常，那么releaseConnection依旧为true。
response = realChain.proceed(request, streamAllocation, null, null);
releaseConnection = false;
} catch (RouteException e) {
//todo 路由异常，连接未成功，请求还没发出去
//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) {
//todo 请求发出去了，但是和服务器通信失败了。(socket流正在读写数据的时候断开连接)
// HTTP2才会抛出ConnectionShutdownException。所以对于HTTP1 requestSendStarted一定是true
//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.
//todo 不是前两种的失败，那直接关闭清理所有资源
if (releaseConnection) {
streamAllocation.streamFailed(null);
streamAllocation.release();
}
}
//todo 如果进过重试/重定向才成功的，则在本次响应中记录上次响应的情况
//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();
}
//todo 处理3和4xx的一些状态码，如301 302重定向
Request followUp = followUpRequest(response, streamAllocation.route());
if (followUp == null) {
if (!forWebSocket) {
streamAllocation.release();
}
return response;
}
closeQuietly(response.body());
//todo 限制最大 followup 次数为20次
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());
}
//todo 判断是不是可以复用同一份连接
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;
}
}
此拦while true 循环来等待异常冒泡，
- 请求异常，进行重试
- 路由异常，进行重试
- 不是1和2 释放所有资源
- 果进过重试/重定向才成功的，则在本次响应中记录上次响应的情况
- 处理3和4xx的一些状态码，如301 302重定向
- 限制最大 followup 次数为20次
BridgeInterceptor
侨接拦截器:将HTTP 协议的请求头加入其中，比如host，并添加一些默认行为比如 GZIP。在获得结果后，调用cookie ，并解析Gzip
ublic 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： 是否使用缓存的数据，拿到结果是否缓存
public Response intercept(Chain chain) throws IOException {
//todo 通过url的md5数据 从文件缓存查找 （GET请求才有缓存）
Response cacheCandidate = cache != null
? cache.get(chain.request())
: null;
long now = System.currentTimeMillis();
//todo 缓存策略:根据各种条件(请求头)组成 请求与缓存
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.
}
//todo 没有网络请求也没有缓存
//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();
}
//todo 没有请求，肯定就要使用缓存
//If we don't need the network, we're done.
if (networkRequest == null) {
return cacheResponse.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.build();
}
//todo 去发起请求
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) {
//todo 服务器返回304无修改，那就使用缓存的响应修改了时间等数据后作为本次请求的响应
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());
}
}
//todo 走到这里说明缓存不可用 那就使用网络的响应
Response response = networkResponse.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.networkResponse(stripBody(networkResponse))
.build();
//todo 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;
}
决定是否需要使用缓存数据，networkRequest，cacheResponse 来决定的
| networkRequest | cacheResponse | 说明 | |
|---|---|---|---|
| null | not null | 直接使用缓存 | |
| not null | null | 发起网路 | --- |
| not null | not null | 发起缓存，得到304 更新缓存返回 | |
| null | null | 直接返回504 |
ConnectInterceptor
链接拦截器：负责找到链接，获得对应的Socket流，不进行额外的处理
@Override
public Response intercept(Chain chain) throws IOException {
RealInterceptorChain realChain = (RealInterceptorChain) chain;
Request request = realChain.request();
//获取可复用流
StreamAllocation streamAllocation = realChain.streamAllocation();
boolean doExtensiveHealthChecks = !request.method().equals("GET");
//创建输出流
HttpCodec httpCodec = streamAllocation.newStream(client, doExtensiveHealthChecks);
//根据HTTP/1.x（keep-alive）和HTTP/2（流复用）的复用机制，发起连接
RealConnection connection = streamAllocation.connection();
return realChain.proceed(request, streamAllocation, httpCodec, connection);
}
寻找健康的链接链接，可复用的复用，不可复用重新创建链接；并开启定期清理无用链接线程池
CallServerInterceptor
请求服务拦截器： 和服务器进行真正的通信，向服务器发送数据吗，解析读取响应的数据
public final class CallServerInterceptor implements Interceptor
@Override
public Response intercept(Chain chain) throws IOException {
//这些对象在前面的Interceptor都已经创建完毕
RealInterceptorChain realChain = (RealInterceptorChain) chain;
//流处理工具
HttpCodec httpCodec = realChain.httpStream();
//流分配调度
StreamAllocation streamAllocation = realChain.streamAllocation();
//真正的链接
RealConnection connection = (RealConnection) realChain.connection();
//请求
Request request = realChain.request();
long sentRequestMillis = System.currentTimeMillis();
//回调接口
realChain.eventListener().requestHeadersStart(realChain.call());
//1. 写入请求头
//这个方法分析一下，这个httpCodec我们走http2.0分支的
httpCodec.writeRequestHeaders(request);
realChain.eventListener().requestHeadersEnd(realChain.call(), request);
Response.Builder responseBuilder = null;
//检测一下是否是允许的请求方式，body不为空
if (HttpMethod.permitsRequestBody(request.method()) && request.body() != null) {
//一个小知识点，关于"Expect: 100-continue"的
//1、http 100-continue用于客户端在发送POST数据给服务器前，征询服务器情况，看服务器是否处理POST的数据，如果不处理，客户端则不上传POST数据，如果处理，则POST上传数据。在现实应用中，通过在POST大数据时，才会使用100-continue协议。
//2、客户端策略。
//1）如果客户端有POST数据要上传，可以考虑使用100-continue协议。加入头{"Expect":"100-continue"}
//2）如果没有POST数据，不能使用100-continue协议，因为这会让服务端造成误解。
//3）并不是所有的Server都会正确实现100-continue协议，如果Client发送Expect:100-continue消息后，在timeout时间内无响应，Client需要立马上传POST数据。
//4）有些Server会错误实现100-continue协议，在不需要此协议时返回100，此时客户端应该忽略。
//3、服务端策略。
//1）正确情况下，收到请求后，返回100或错误码。
//2）如果在发送100-continue前收到了POST数据（客户端提前发送POST数据），则不发送100响应码(略去)。
//如果请求中存在“Expect：100-continue”标头，请在发送请求主体之前等待“HTTP / 1.1 100 Continue”响应。
// 如果我们没有得到，请返回我们得到的内容（例如4xx响应），不继续发送请求主体。
if ("100-continue".equalsIgnoreCase(request.header("Expect"))) {
//flush请求头
httpCodec.flushRequest();
realChain.eventListener().responseHeadersStart(realChain.call());
//这个方法会进入等待，当后台返回100应答的时候responseBuilder 为空
//点进去就是调用了stream的takeHeaders()方法获取读到的header
responseBuilder = httpCodec.readResponseHeaders(true);
}
//2 写入请求体
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();
}
}
//关闭request输出
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();
//4 读取响应体
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);
//空的返回
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 {
//组织body
response = response.newBuilder()
.body(httpCodec.openResponseBody(response))
.build();
}
//标记noNewStreams
if ("close".equalsIgnoreCase(response.request().header("Connection"))
|| "close".equalsIgnoreCase(response.header("Connection"))) {
streamAllocation.noNewStreams();
}
//协议异常
if ((code == 204 || code == 205) && response.body().contentLength() > 0) {
throw new ProtocolException(
"HTTP " + code + " had non-zero Content-Length: " + response.body().contentLength());
}
//最终返回
return response;
}
}
//Http2Codec的writeRequestHeaders()方法
@Override public void writeRequestHeaders(Request request) throws IOException {
if (stream != null) return;
boolean hasRequestBody = request.body() != null;
//组装一下header
List<Header> requestHeaders = http2HeadersList(request);
//newStream方法是Http2Connection的，继续追踪下去
stream = connection.newStream(requestHeaders, hasRequestBody);
stream.readTimeout().timeout(chain.readTimeoutMillis(), TimeUnit.MILLISECONDS);
stream.writeTimeout().timeout(chain.writeTimeoutMillis(), TimeUnit.MILLISECONDS);
}
/**
* Returns a new locally-initiated stream.
* @param out true to create an output stream that we can use to send data to the remote peer.
* Corresponds to {@code FLAG_FIN}.
*/
//Http2Connection的newStream（）方法
public Http2Stream newStream(List<Header> requestHeaders, boolean out) throws IOException {
return newStream(0, requestHeaders, out);
}
private Http2Stream newStream(
int associatedStreamId, List<Header> requestHeaders, boolean out) throws IOException {
boolean outFinished = !out;
boolean inFinished = false;
boolean flushHeaders;
Http2Stream stream;
int streamId;
synchronized (writer) {
synchronized (this) {
if (nextStreamId > Integer.MAX_VALUE / 2) {
shutdown(REFUSED_STREAM);
}
if (shutdown) {
throw new ConnectionShutdownException();
}
streamId = nextStreamId;
nextStreamId += 2;
stream = new Http2Stream(streamId, this, outFinished, inFinished, null);
flushHeaders = !out || bytesLeftInWriteWindow == 0L || stream.bytesLeftInWriteWindow == 0L;
if (stream.isOpen()) {
//这个new出来的stream也保存在streams里，是个map
//同时会返回赋值给Http2Codec的成员变量stream
//每次读到数据都会调用Http2Connection的readers()方法把数据存到相应的stream
streams.put(streamId, stream);
}
}
if (associatedStreamId == 0) {
//走着里，完成写header操作
writer.synStream(outFinished, streamId, associatedStreamId, requestHeaders);
} else if (client) {
throw new IllegalArgumentException("client streams shouldn't have associated stream IDs");
} else { // HTTP/2 has a PUSH_PROMISE frame.
writer.pushPromise(associatedStreamId, streamId, requestHeaders);
}
}
if (flushHeaders) {
writer.flush();
}
return stream;
}
