tomcat启动设备未就绪
Launching suspend functions in Kotlin can be a complicated affair. Managing your CoroutineScope and making sure exceptions are handled properly can be confusing and easy to forget.
在Kotlin中启动suspend功能可能很复杂。 管理您的CoroutineScope并确保正确处理了异常会造成混乱，并且容易忘记。
In Android, when using the ViewModel or Lifecycle specific scopes this gets much easier. We let the Android system provide a CoroutineScope and manage killing our coroutines when the lifecycle of those things end.
在Android中，使用ViewModel或Lifecycle特定范围时，这变得容易得多。 我们让Android系统提供一个CoroutineScope并在这些生命周期结束时管理杀死我们的协程。
fun getObjectFromNetwork() { viewModelScope.launch { val response = networkRepository.getObject() }}However, there are cases when exceptions can be thrown from the CoroutineScope. A real life example I experienced recently was a SocketTimeoutException that was thrown from a Retrofit call I was making using a suspend function. The result is an Android app crash, which is definitely not desired when network calls can result in many different thrown exceptions.
但是，在某些情况下，可以从CoroutineScope抛出异常。 我最近遇到的一个现实生活中的例子是SocketTimeoutException ，它是我通过使用suspend函数进行的Retrofit调用引发的。 结果是Android应用程序崩溃 ，当网络调用会导致许多不同的引发异常时，绝对不希望发生此故障 。
The Kotlin CoroutineExceptionHandler can help us more easily handle exceptions thrown from our Coroutine scope, but it requires us to register the exception handler when we launch a new coroutine so we properly handle nested exceptions.
Kotlin CoroutineExceptionHandler可以帮助我们更轻松地处理从Coroutine范围引发的异常，但是它要求我们在launch新的协程时注册异常处理程序，以便我们正确处理嵌套的异常 。
val coroutineExceptionHandler = CoroutineExceptionHandler { coroutineContext, throwable -> // handle thrown exceptions from coroutine scope throwable.printStackTrace()}fun getObjectFromNetwork() { viewModelScope.launch(coroutineExceptionHandler) { val response = networkRepository.getObject() }}Now, while the ViewModel is probably a logical place for handling exceptions in network calls, there are a lot of exceptions that are thrown irregularly from your app that aren’t part of the logical flow of a network call. Using Retrofit as an example, most network calls should return a Response with a body() or errorBody() to handle instead of edge-cases where actual exceptions, like a SocketTimeoutException is thrown. It might be worth it to you to abstract this error handling away from your ViewModel to help minimize boiler plate.
现在，虽然ViewModel可能是处理网络调用中异常的逻辑位置，但您的应用程序中有很多异常抛出，这些异常不属于网络调用的逻辑流程。 以Retrofit为例，大多数网络调用应返回一个带有body()或errorBody()的Response来处理，而不是抛出抛出诸如SocketTimeoutException类的实际异常的边缘情况。 您可能需要从ViewModel抽象出此错误处理，以最大程度地减少样板，这对您来说是值得的。
To try this out, let’s leverage the power of Kotlin extensions to create a safeLaunch method on CoroutineScope that can apply a default CoroutineExceptionHandler.
尝试了这一点，让我们利用Kotlin扩展的力量创造一个safeLaunch的方法CoroutineScope可以应用默认CoroutineExceptionHandler 。
fun CoroutineScope.safeLaunch(launchBody: suspend () -> Unit): Job { val coroutineExceptionHandler = CoroutineExceptionHandler { coroutineContext, throwable -> // handle thrown exceptions from coroutine scope throwable.printStackTrace() } return this.launch(coroutineExceptionHandler) { launchBody.invoke() }}Now, we can call safeLaunch on any CoroutineScope, like our viewModelScope, to launch a coroutine with this default error handling behavior.
现在，我们可以调用safeLaunch任何CoroutineScope ，像我们viewModelScope ，发动协程与此默认的错误处理行为。
fun getObjectFromNetwork() { viewModelScope.safeLaunch { val response = networkRepository.getObject() }}There you have it! A nicely-encapsulated method to launch suspend functions knowing that we won’t see random app crashes because of an unhandled Throwable.
你有它！ 一个很好封装的方法，可以启动suspend函数，因为我们不会因未处理的Throwable导致应用程序崩溃而不会崩溃。
If we wanted safeLaunch to be the core CoroutineScope launch method in our app, we can even improve the extension a bit to allow users the flexibility of passing their own CoroutineExceptionHandler instead of using the default.
如果我们希望safeLaunch成为应用程序中的核心CoroutineScope启动方法，我们甚至可以稍微扩展一下扩展，以允许用户灵活地传递自己的CoroutineExceptionHandler而不是使用默认值。
val coroutineExceptionHandler = CoroutineExceptionHandler { coroutineContext, throwable -> throwable.printStackTrace()}fun CoroutineScope.safeLaunch( exceptionHandler: CoroutineExceptionHandler = coroutineExceptionHandler, launchBody: suspend () -> Unit): Job { return this.launch(exceptionHandler) { launchBody.invoke() }}The same day I wrote this article, Manuel Vivo and Florina Muntenescu from the Android developer relations team released a really good series on coroutines, including the subject of coroutine exceptions. Check it out if you want to learn more about coroutines and how to manage them.
在我撰写本文的同一天，Android开发人员关系团队的Manuel Vivo和Florina Muntenescu发布了有关协程的非常好的系列文章，其中包括协程异常主题。 如果您想了解有关协程以及如何管理它们的更多信息，请查看。
Intro to Coroutines
协程简介
Cancelling Coroutines
取消协程
Exceptions in Coroutines
协程中的例外
Originally posted on ajkueterman.dev
最初发布在 ajkueterman.dev
翻译自: https://medium.com/swlh/safely-launch-exception-ready-coroutines-31804de77993
tomcat启动设备未就绪
