Do I need to handle exception in executorservice

Question

Did I need to handle runtime exception in executorservice? I tried an example in spring boot web application, the code will still execute despite of exception

Here is the code:

@RestController
class WelcomeController {
    ExecutorService es = Executors.newSingleThreadExecutor();

    @GetMapping("/sayhi")
    public String sayHi() {
        es.submit(() -> {
            System.out.println("hello");

            int a = 0;
            if (10 / a == 1) {

            }
        });

        return "hi";
    }
}

If you are talking about `submit` then it only throws `RuntimeExceptions` see https://stackoverflow.com/questions/6115896/java-checked-vs-unchecked-exception-explanation — Scary Wombat, Sep 07 '18 at 00:15
Read from somewhere that people say I should handle exceptions in threads. Like this article https://medium.com/@aozturk/how-to-handle-uncaught-exceptions-in-java-abf819347906 — 王子1986, Sep 07 '18 at 00:17
@NathanHughes will this handled exception kill the application eventually? — 王子1986, Sep 07 '18 at 00:30
No. It’s just that the application does more work than it should have to. — Nathan Hughes, Sep 07 '18 at 00:33
@NathanHughes hmmm, what’s the additional work does the application do? I tried to monitor application threads with visualvm. The only difference I can notice is the thread status , one is monitor , another is idle. — 王子1986, Sep 07 '18 at 00:39
Threads are OS resources. The application has to obtain replacements when they get terminated. With a toy example you won’t see a problem. — Nathan Hughes, Sep 07 '18 at 00:41
@NathanHughes use a big block try catch or just leave the code like that, which one is more practical? Threads creation seems very cheap. — 王子1986, Sep 07 '18 at 00:45

Nathan Hughes · Answer 1 · 2018-09-07T00:31:58.447

When an exception is thrown in one thread it doesn’t propagate to other threads unless you do something to make it do that (like using a Future). Here the thread causes an exception and dies, but the rest of the program isn’t affected.

The executor creates a replacement for the lost thread, see the api doc:

Creates an Executor that uses a single worker thread operating off an unbounded queue, and uses the provided ThreadFactory to create a new thread when needed. Unlike the otherwise equivalent newFixedThreadPool(1, threadFactory) the returned executor is guaranteed not to be reconfigurable to use additional threads.

It would seem to me like a good idea to have tasks handle exceptions that they cause. Otherwise the thread dies and the pool has to start a new one to replace it. This is basically what the article linked in the comments says.

score 0 · Answer 2 · answered Sep 07 '18 at 00:21

0

You supposed to keep the return value Future

and use Future.get() to interogate if there was an unhandled Exception

answered Sep 07 '18 at 00:21

Dapeng

1,704
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What about I just want to fire and forget – 王子1986 Sep 07 '18 at 00:31

Do I need to handle exception in executorservice

2 Answers2