在 CompletableFuture 的 whenComplete() 之前返回的方法

Question

I'm using CompletableFuture's whenComplete for the first time.

In my use case I want to call a REST api and fetch its result. Perform some operations on those results and return the output.

I thought of making this REST call using CompletableFuture.supplyAsync() & use whenComplete() to fetch the result.

Below is the sample code I'm currently using:

1. String myOutput = null;
2. CompletableFuture.supplyAsync(() -> callMyRestService(myUrl))
3.    .whenComplete((myResponseWrapper, exception) -> {
4.        if (exception != null) {
5.            logUtil.error("GET", exception.toString());
6.        } else if (myResponseWrapper != null) {
7.          myOutput = myResponseWrapper.getName();
8.        }
9.    });
10. return myOutput;

But upon debugging I noticed that after executing line #2, #10 is executed and function returns, then later execution of on #3 starts.

This is not what I expecting. I wanted it to be sequential.

How can I achieve this?

PS On side note, I did not wanted to CompletableFuture.get(), because the way it does not handle InterruptedException .

Answer 1

You are deliberately using something that's async and then complaining it's not synchronous... Remove the CompletableFuture entirely if you want it to be synchronous.

try  {
    SomeClass myResponseWrapper = callMyRestService(myUrl)
    return myResponseWrapper.getName();
}
catch (Exception e) {
    logUtil.error("GET", exception.toString());
}