OkHttp
Version 4.4.0
OkHttpClient 创建
可以通过建造者模式进行参数设定，会初始化调度器Dispatcher。
请求创建
请求的创建等都使用了建造者模式。
异步请求
请求真正的执行时RealCall类，同步请求使用execute，异步请求使用enqueue。
Realcall#enqueue 调用了 client.dispatcher#enqueue(AsyncCall)
// RealCall#enqueue
override fun enqueue(responseCallback: Callback) {
synchronized(this) {
check(!executed) { "Already Executed" }
executed = true
}
callStart()
client.dispatcher.enqueue(AsyncCall(responseCallback))
}//Dispatcher#enqueue
internal fun enqueue(call: AsyncCall) {
synchronized(this) {
//添加到等待队列
readyAsyncCalls.add(call)
// Mutate the AsyncCall so that it shares the AtomicInteger of an existing running call to
// the same host.
if (!call.call.forWebSocket) {
val existingCall = findExistingCallWithHost(call.host)
if (existingCall != null) call.reuseCallsPerHostFrom(existingCall)
}
}
promoteAndExecute()
}
private fun promoteAndExecute(): Boolean {
this.assertThreadDoesntHoldLock()
val executableCalls = mutableListOf<AsyncCall>()
val isRunning: Boolean
synchronized(this) {
val i = readyAsyncCalls.iterator()
//将等待中的请求放入可执行队列
while (i.hasNext()) {
val asyncCall = i.next()
if (runningAsyncCalls.size >= this.maxRequests) break // Max capacity.
if (asyncCall.callsPerHost.get() >= this.maxRequestsPerHost) continue // Host max capacity.
i.remove()
asyncCall.callsPerHost.incrementAndGet()
executableCalls.add(asyncCall)
runningAsyncCalls.add(asyncCall)
}
isRunning = runningCallsCount() > 0
}
//将可执行请求放入线程池
for (i in 0 until executableCalls.size) {
val asyncCall = executableCalls[i]
asyncCall.executeOn(executorService)
}
return isRunning
}先加入到等待队列中，然后通过 promoteAndExecute 方法，将等待队列中可以执行的请求添加到可执行列表中（需要满足限制条件：并发请求数量、相同host并发请求数量、线程数等等），同时添加到执行中列表中，然后通过线程池执行。
AsyncCall#run
//AsyncCall#run
override fun run() {
threadName("OkHttp ${redactedUrl()}") {
var signalledCallback = false
timeout.enter()
try {
val response = getResponseWithInterceptorChain()
signalledCallback = true
responseCallback.onResponse(this@RealCall, response)
} catch (e: IOException) {
if (signalledCallback) {
// Do not signal the callback twice!
Platform.get().log("Callback failure for ${toLoggableString()}", Platform.INFO, e)
} else {
responseCallback.onFailure(this@RealCall, e)
}
} catch (t: Throwable) {
cancel()
if (!signalledCallback) {
val canceledException = IOException("canceled due to $t")
canceledException.addSuppressed(t)
responseCallback.onFailure(this@RealCall, canceledException)
}
throw t
} finally {
client.dispatcher.finished(this)
}
}
}执行请求的方法 RealCall#getResponseWithInterceptorChain(),这个方法中会将用户自定义的拦截器加上已经按职责分离的所有必须拦截器构造一个RealInterceptorChain，然后调用它的proceed 方法处理请求。
RealCall#getResponseWithInterceptorChain
//RealCall#getResponseWithInterceptorChain()
internal fun getResponseWithInterceptorChain(): Response {
// Build a full stack of interceptors.
val interceptors = mutableListOf<Interceptor>()
//添加用户自定义的拦截器
interceptors += client.interceptors
interceptors += RetryAndFollowUpInterceptor(client)
interceptors += BridgeInterceptor(client.cookieJar)
interceptors += CacheInterceptor(client.cache)
interceptors += ConnectInterceptor
if (!forWebSocket) {
interceptors += client.networkInterceptors
}
//添加用于发送请求的拦截器
interceptors += CallServerInterceptor(forWebSocket)
val chain = RealInterceptorChain(
call = this,
interceptors = interceptors,
index = 0,
exchange = null,
request = originalRequest,
connectTimeoutMillis = client.connectTimeoutMillis,
readTimeoutMillis = client.readTimeoutMillis,
writeTimeoutMillis = client.writeTimeoutMillis
)
var calledNoMoreExchanges = false
try {
val response = chain.proceed(originalRequest)
if (isCanceled()) {
response.closeQuietly()
throw IOException("Canceled")
}
return response
} catch (e: IOException) {
calledNoMoreExchanges = true
throw noMoreExchanges(e) as Throwable
} finally {
if (!calledNoMoreExchanges) {
noMoreExchanges(null)
}
}
}请求处理使用了连接器链完成-责任链模式。
RealInterceptorChain#proceed
override fun proceed(request: Request): Response {
check(index < interceptors.size)
calls++
if (exchange != null) {
check(exchange.connection.supportsUrl(request.url)) {
"network interceptor ${interceptors[index - 1]} must retain the same host and port"
}
check(calls == 1) {
"network interceptor ${interceptors[index - 1]} must call proceed() exactly once"
}
}
// Call the next interceptor in the chain.
val next = copy(index = index + 1, request = request)
val interceptor = interceptors[index]
@Suppress("USELESS_ELVIS")
val response = interceptor.intercept(next) ?: throw NullPointerException(
"interceptor $interceptor returned null")
if (exchange != null) {
check(index + 1 >= interceptors.size || next.calls == 1) {
"network interceptor $interceptor must call proceed() exactly once"
}
}
check(response.body != null) { "interceptor $interceptor returned a response with no body" }
return response
}intercept 方法参数为 RealInterceptorChain ，该方法中需要执行 chain.proceed 进行传递。
如果要在响应前执行操作，那么可以放在 chain.proceed 之前；如果要在收到响应后再处理，可以先调用 chain.proceed 获取响应，然后再操作.
请求完成后通过 dispatcher.finish方法，将执行完的call移除队列，并在符合条件的情况下执行等待队列中的请求并添加到运行中队列。
同步请求
// RealCall#execute()
override fun execute(): Response {
synchronized(this) {
check(!executed) { "Already Executed" }
executed = true
}
timeout.enter()
callStart()
try {
client.dispatcher.executed(this)
return getResponseWithInterceptorChain()
} finally {
client.dispatcher.finished(this)
}
}dispatcher 只是将 call 添加到了运行中队列：
@Synchronized internal fun executed(call: RealCall) {
runningSyncCalls.add(call)
}Dispatcher
Dispatcher 有三个队列
//等待中的异步请求
private val readyAsyncCalls = ArrayDeque<AsyncCall>()
//处理中的异步请求
private val runningAsyncCalls = ArrayDeque<AsyncCall>()
//处理中的同步请求
private val runningSyncCalls = ArrayDeque<RealCall>()线程池创建
val executorService: ExecutorService
get() {
if (executorServiceOrNull == null) {
executorServiceOrNull = ThreadPoolExecutor(0, Int.MAX_VALUE, 60, TimeUnit.SECONDS,
SynchronousQueue(), threadFactory("$okHttpName Dispatcher", false))
}
return executorServiceOrNull!!
}默认情况下创建的线程池，核心线程数是0（没有常驻线程）、存活时间60秒。默认拒绝策略是抛异常。
请求发送
BridgeInterceptor
主要是将用户创建的请求调整为HTTP 协议格式，并将原始响应组成成Response。
override fun intercept(chain: Interceptor.Chain): Response {
val userRequest = chain.request()
val requestBuilder = userRequest.newBuilder()
val body = userRequest.body
//------------------处理请求--------------
if (body != null) {
val contentType = body.contentType()
if (contentType != null) {
requestBuilder.header("Content-Type", contentType.toString())
}
val contentLength = body.contentLength()
if (contentLength != -1L) {
requestBuilder.header("Content-Length", contentLength.toString())
requestBuilder.removeHeader("Transfer-Encoding")
} else {
requestBuilder.header("Transfer-Encoding", "chunked")
requestBuilder.removeHeader("Content-Length")
}
}
if (userRequest.header("Host") == null) {
requestBuilder.header("Host", userRequest.url.toHostHeader())
}
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.
var transparentGzip = false
if (userRequest.header("Accept-Encoding") == null && userRequest.header("Range") == null) {
transparentGzip = true
requestBuilder.header("Accept-Encoding", "gzip")
}
val cookies = cookieJar.loadForRequest(userRequest.url)
if (cookies.isNotEmpty()) {
requestBuilder.header("Cookie", cookieHeader(cookies))
}
if (userRequest.header("User-Agent") == null) {
requestBuilder.header("User-Agent", userAgent)
}
//-----------------处理请求 Done--------------------
val networkResponse = chain.proceed(requestBuilder.build())
//-----------------开始处理响应----------------------
cookieJar.receiveHeaders(userRequest.url, networkResponse.headers)
val responseBuilder = networkResponse.newBuilder()
.request(userRequest)
if (transparentGzip &&
"gzip".equals(networkResponse.header("Content-Encoding"), ignoreCase = true) &&
networkResponse.promisesBody()) {
val responseBody = networkResponse.body
if (responseBody != null) {
val gzipSource = GzipSource(responseBody.source())
val strippedHeaders = networkResponse.headers.newBuilder()
.removeAll("Content-Encoding")
.removeAll("Content-Length")
.build()
responseBuilder.headers(strippedHeaders)
val contentType = networkResponse.header("Content-Type")
responseBuilder.body(RealResponseBody(contentType, -1L, gzipSource.buffer()))
}
}
return responseBuilder.build()
}CallServerInterceptor
真正用于发送请求的拦截器，这也是拦截器列表里最后一个拦截器。
override fun intercept(chain: Interceptor.Chain): Response {
val realChain = chain as RealInterceptorChain
val exchange = realChain.exchange!!
val request = realChain.request
val requestBody = request.body
val sentRequestMillis = System.currentTimeMillis()
exchange.writeRequestHeaders(request)
var invokeStartEvent = true
var responseBuilder: Response.Builder? = null
if (HttpMethod.permitsRequestBody(request.method) && requestBody != 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".equals(request.header("Expect"), ignoreCase = true)) {
exchange.flushRequest()
responseBuilder = exchange.readResponseHeaders(expectContinue = true)
exchange.responseHeadersStart()
invokeStartEvent = false
}
if (responseBuilder == null) {
if (requestBody.isDuplex()) {
// Prepare a duplex body so that the application can send a request body later.
exchange.flushRequest()
val bufferedRequestBody = exchange.createRequestBody(request, true).buffer()
requestBody.writeTo(bufferedRequestBody)
} else {
// Write the request body if the "Expect: 100-continue" expectation was met.
val bufferedRequestBody = exchange.createRequestBody(request, false).buffer()
requestBody.writeTo(bufferedRequestBody)
bufferedRequestBody.close()
}
} else {
exchange.noRequestBody()
if (!exchange.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.
exchange.noNewExchangesOnConnection()
}
}
} else {
exchange.noRequestBody()
}
if (requestBody == null || !requestBody.isDuplex()) {
exchange.finishRequest()
}
if (responseBuilder == null) {
responseBuilder = exchange.readResponseHeaders(expectContinue = false)!!
if (invokeStartEvent) {
exchange.responseHeadersStart()
invokeStartEvent = false
}
}
var response = responseBuilder
.request(request)
.handshake(exchange.connection.handshake())
.sentRequestAtMillis(sentRequestMillis)
.receivedResponseAtMillis(System.currentTimeMillis())
.build()
var 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 status.
responseBuilder = exchange.readResponseHeaders(expectContinue = false)!!
if (invokeStartEvent) {
exchange.responseHeadersStart()
}
response = responseBuilder
.request(request)
.handshake(exchange.connection.handshake())
.sentRequestAtMillis(sentRequestMillis)
.receivedResponseAtMillis(System.currentTimeMillis())
.build()
code = response.code
}
exchange.responseHeadersEnd(response)
response = if (forWebSocket && code == 101) {
// Connection is upgrading, but we need to ensure interceptors see a non-null response body.
response.newBuilder()
.body(EMPTY_RESPONSE)
.build()
} else {
response.newBuilder()
.body(exchange.openResponseBody(response))
.build()
}
if ("close".equals(response.request.header("Connection"), ignoreCase = true) ||
"close".equals(response.header("Connection"), ignoreCase = true)) {
exchange.noNewExchangesOnConnection()
}
if ((code == 204 || code == 205) && response.body?.contentLength() ?: -1L > 0L) {
throw ProtocolException(
"HTTP $code had non-zero Content-Length: ${response.body?.contentLength()}")
}
return response
}主要借助Exchange来发送请求和读取响应,而 Exchange 又借助 ExchangeCodec 编解码器来进行处理。ExchangeCodec 是一个接口，实现类有 Http1ExchangeCodec 和Http2ExchangeCodec，分别对应HTTP 1.1 和 HTTP 2。
连接的初始化在 ConnectInterceptor 中进行，调用了call.initExchange 方法
@Throws(IOException::class)
override fun intercept(chain: Interceptor.Chain): Response {
val realChain = chain as RealInterceptorChain
val exchange = realChain.call.initExchange(chain)
val connectedChain = realChain.copy(exchange = exchange)
return connectedChain.proceed(realChain.request)
}RealInterceptorChain#initExchange
internal fun initExchange(chain: RealInterceptorChain): Exchange {
synchronized(connectionPool) {
check(!noMoreExchanges) { "released" }
check(exchange == null)
}
val codec = exchangeFinder!!.find(client, chain)
val result = Exchange(this, eventListener, exchangeFinder!!, codec)
this.interceptorScopedExchange = result
synchronized(connectionPool) {
this.exchange = result
this.exchangeRequestDone = false
this.exchangeResponseDone = false
return result
}
}ExchangeFinder#find
fun find(
client: OkHttpClient,
chain: RealInterceptorChain
): ExchangeCodec {
try {
val resultConnection = findHealthyConnection(
connectTimeout = chain.connectTimeoutMillis,
readTimeout = chain.readTimeoutMillis,
writeTimeout = chain.writeTimeoutMillis,
pingIntervalMillis = client.pingIntervalMillis,
connectionRetryEnabled = client.retryOnConnectionFailure,
doExtensiveHealthChecks = chain.request.method != "GET"
)
return resultConnection.newCodec(client, chain)
} catch (e: RouteException) {
trackFailure(e.lastConnectException)
throw e
} catch (e: IOException) {
trackFailure(e)
throw RouteException(e)
}
}RealConnection#newCodec
internal fun newCodec(client: OkHttpClient, chain: RealInterceptorChain): ExchangeCodec {
val socket = this.socket!!
val source = this.source!!
val sink = this.sink!!
val http2Connection = this.http2Connection
return if (http2Connection != null) {
Http2ExchangeCodec(client, this, chain, http2Connection)
} else {
socket.soTimeout = chain.readTimeoutMillis()
source.timeout().timeout(chain.readTimeoutMillis.toLong(), MILLISECONDS)
sink.timeout().timeout(chain.writeTimeoutMillis.toLong(), MILLISECONDS)
Http1ExchangeCodec(client, this, source, sink)
}
}缓存处理
默认的缓存逻辑在 CacheInterceptor 中，使用DiskLruCache。
override fun intercept(chain: Interceptor.Chain): Response {
val cacheCandidate = cache?.get(chain.request())
val now = System.currentTimeMillis()
val strategy = CacheStrategy.Factory(now, chain.request(), cacheCandidate).compute()
val networkRequest = strategy.networkRequest
val cacheResponse = strategy.cacheResponse
cache?.trackResponse(strategy)
if (cacheCandidate != null && cacheResponse == null) {
// The cache candidate wasn't applicable. Close it.
cacheCandidate.body?.closeQuietly()
}
// If we're forbidden from using the network and the cache is insufficient, fail.
if (networkRequest == null && cacheResponse == null) {
return Response.Builder()
.request(chain.request())
.protocol(Protocol.HTTP_1_1)
.code(HTTP_GATEWAY_TIMEOUT)
.message("Unsatisfiable Request (only-if-cached)")
.body(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()
}
var networkResponse: Response? = 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) {
cacheCandidate.body?.closeQuietly()
}
}
// If we have a cache response too, then we're doing a conditional get.
if (cacheResponse != null) {
if (networkResponse?.code == HTTP_NOT_MODIFIED) {
val 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 {
cacheResponse.body?.closeQuietly()
}
}
val response = networkResponse!!.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.networkResponse(stripBody(networkResponse))
.build()
if (cache != null) {
if (response.promisesBody() && CacheStrategy.isCacheable(response, networkRequest)) {
// Offer this request to the cache.
val cacheRequest = cache.put(response)
return cacheWritingResponse(cacheRequest, response)
}
if (HttpMethod.invalidatesCache(networkRequest.method)) {
try {
cache.remove(networkRequest)
} catch (_: IOException) {
// The cache cannot be written.
}
}
}
return response
}主要逻辑：
校验缓存是否可用
网络不可用、缓存不可用，返回空响应
网络不可用、缓存可用，返回缓存的响应
网络可用、发送请求，如果304，返回缓存可用，
根据最新的响应更新或添加缓存
相关链接
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