Exception Handling
Explore how to manage exceptions in Kotlin asynchronous programming by understanding differences between launch and async functions. Learn to implement CoroutineExceptionHandler and handle failures gracefully in coroutines for more reliable code execution.
We'll cover the following...
Many things can go wrong when making requests to web services, updating databases, accessing a file, and so on. When delegating a task to run asynchronously, we have to be defensive and handle failures gracefully. How we deal with exceptions depends on how we start a coroutine—using launch() or async().
Be Mindful of Structured Concurrency
Unless a scope is explicitly specified, coroutines run in the context and scope of their parent coroutines—called structured concurrency, where the hierarchical structure of coroutines matches the structure of code. This is a good thing as it’s easier to monitor and manage the execution of coroutines that we start. A coroutine doesn’t complete until all its children complete. But this also has some ramifications on how coroutines cooperate with each other and how failures are handled.
By default, when a coroutine fails with an exception, it results in the failure of the parent coroutine as well. Later in this chapter we’ll take a closer look at the behavior of coroutines in the context of structured concurrency and how we can prevent a child coroutine from cancelling a parent coroutine using a SupervisorJob context. In the examples in this section, we’ll use this context to prevent a child coroutine from cancelling its parent when an exception occurs.
launch and exceptions
If we use ...