一个小技巧提升 OkHttp 请求稳定性

技术小黑屋

发布于 2020-01-19 19:03:48

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OkHttp是可以说是Android开发中，每个项目都必需依赖的网络库，我们可以很便捷高效的处理网络请求，极大的提升了编码效率。但是有时候，我们使用OkHttp也会遇到这样的问题

崩溃的stacktrace

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E AndroidRuntime: FATAL EXCEPTION: OkHttp Dispatcher E AndroidRuntime: Process: com.example.okhttpexceptionsample, PID: 13564 E AndroidRuntime: java.lang.NullPointerException: blablabla E AndroidRuntime: at com.example.okhttpexceptionsample.MainActivity$createNPEInterceptor$1.intercept(MainActivity.kt:61) E AndroidRuntime: at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:112) E AndroidRuntime: at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:87) E AndroidRuntime: at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.kt:184) E AndroidRuntime: at okhttp3.RealCall$AsyncCall.run(RealCall.kt:136) E AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) E AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) E AndroidRuntime: at java.lang.Thread.run(Thread.java:784)

为什么会崩溃

从上面的stacktrace，我们可以分析到，发生了NullPointerException。发生了崩溃。

等等，我记得OkHttp有处理异常的情况呢。

嗯，确实，OkHttp有处理异常的情况，比如发生异常会调用onFailure。比如下面的Callback的内容介绍。

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interface Callback { /** * Called when the request could not be executed due to cancellation, a connectivity problem or * timeout. Because networks can fail during an exchange, it is possible that the remote server * accepted the request before the failure. */ fun onFailure(call: Call, e: IOException) /** * Called when the HTTP response was successfully returned by the remote server. The callback may * proceed to read the response body with [Response.body]. The response is still live until its * response body is [closed][ResponseBody]. The recipient of the callback may consume the response * body on another thread. * * Note that transport-layer success (receiving a HTTP response code, headers and body) does not * necessarily indicate application-layer success: `response` may still indicate an unhappy HTTP * response code like 404 or 500. */ @Throws(IOException::class) fun onResponse(call: Call, response: Response) }

是的，

OkHttp只处理了IOException的情况，
NullPointerException不是IOException的子类

所以没有被处理,发生了崩溃。

那么有没有办法解决，让这种崩溃不发生，对用户不进行干扰呢？其实是可以的。

使用Interceptor

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package com.example.okhttpexceptionsample import okhttp3.Interceptor import okhttp3.Response import java.io.IOException /** * 对于Interceptor的intercept中可能出现的Throwable包裹成IOExceptionWrapper，转成网络请求失败，而不是应用崩溃 */ class SafeGuardInterceptor : Interceptor { override fun intercept(chain: Interceptor.Chain): Response { try { return chain.proceed(chain.request()) } catch (t: Throwable) { throw IOExceptionWrapper("SafeGuarded when requesting ${chain.request().url}", t) } } } /** * 将chain.proceed处理中发生的Throwable包装成IOExceptionWrapper */ class IOExceptionWrapper(message: String?, cause: Throwable?) : IOException(message, cause)

上面的代码，我们将任何Throwable的转成IOExceptionWrapper（伪装成IOException），然后添加到OkHttpClient中

1 2 3 4 5	fun createOKHttpClient(): OkHttpClient { return OkHttpClient.Builder() .addInterceptor(SafeGuardInterceptor()) .build() }

当我们再次执行有NPE的代码，日志就发生了改变(不再是崩溃的日志，而是异常的日志)

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W System.err: com.example.okhttpexceptionsample.IOExceptionWrapper: SafeGuarded=blablabla W System.err: at com.example.okhttpexceptionsample.SafeGuardInterceptor.intercept(SafeGuardInterceptor.kt:12) W System.err: at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:112) W System.err: at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:87) W System.err: at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.kt:184) W System.err: at okhttp3.RealCall$AsyncCall.run(RealCall.kt:136) W System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) W System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) W System.err: at java.lang.Thread.run(Thread.java:784) W System.err: Caused by: java.lang.NullPointerException: blablabla W System.err: at com.example.okhttpexceptionsample.MainActivity$createNPEInterceptor$1.intercept(MainActivity.kt:61) W System.err: at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:112) W System.err: at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.kt:87) W System.err: at com.example.okhttpexceptionsample.SafeGuardInterceptor.intercept(SafeGuardInterceptor.kt:10) W System.err: ... 7 more

上述需要注意两点