OkHttp 原理解析 - 线程调度 

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// 基本使用

OkHttpClient.newCall(Request).enqueue(Callback)

线程调度

  1. newCall 返回 RealCall 对象

  2. 调用 RealCall 对象的 enqueue 方法：

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    // RealCall.class
      override fun enqueue(responseCallback: Callback) {
        synchronized(this) {
          check(!executed) { "Already Executed" }
          executed = true
        }
        callStart() // 调用前期准备，如添加监听
        3. 使用调度器将 call 加入队列，AsyncCall 是 RealCall 内部类，持有 RealCall 对象 
        client.dispatcher.enqueue(AsyncCall(responseCallback)) 
      }

  3. 使用调度器将 call 加入队列

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    // Dispatcher.class
      internal fun enqueue(call: AsyncCall) {
        synchronized(this) {
          readyAsyncCalls.add(call)
          if (!call.call.forWebSocket) {
            val existingCall = findExistingCallWithHost(call.host)
            if (existingCall != null) call.reuseCallsPerHostFrom(existingCall)
          }
        }
        promoteAndExecute() // 4. 从 readyAsyncCalls 中拿出 call 并放入 runningAsyncCalls，执行任务
      }

  4. promoteAndExecute()
    每当 maxRequests/maxRequestsPerHost/call 调用 enqueue/call finish，都会执行promoteAndExecute()

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    private fun promoteAndExecute(): Boolean {
     	this.assertThreadDoesntHoldLock()
       val executableCalls = mutableListOf<AsyncCall>()
       val isRunning: Boolean
       synchronized(this) {
         val i = readyAsyncCalls.iterator()
         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()
           // 将 call 加入可执行列表
           executableCalls.add(asyncCall)
           // 将 call 加入运行中列表
           runningAsyncCalls.add(asyncCall)
         }
         isRunning = runningCallsCount() > 0
       }
       for (i in 0 until executableCalls.size) {
         // 遍历可执行列表中的任务并放入线程池 executorService 中执行
         val asyncCall = executableCalls[i]
         asyncCall.executeOn(executorService)
       }
       return isRunning
     }

实用工具

  • 更新token
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[OkHttpClient].authenticator(object : Authenticator {
            override fun authenticate(route: Route?, response: Response): Request? {
                return response.request.newBuilder()
                    .header("Auth", "[NEW_TOKEN]")
                    .build()
            }
        })