[英]use of CompletableFuture.supplyAsync and CompletableFuture.completedFuture within @Async annotation in spring boot
我有以下方法:
@EnableAsync
@Service
Class MyService{
private String processRequest() {
log.info("Start processing request");
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
log.info("Completed processing request");
return RESULT;
}
@Async
public CompletableFuture<String> getSupplyAsyncResult(){
CompletableFuture<String> future
= CompletableFuture.supplyAsync(this::processRequest);
return future;
}
@Async
public CompletableFuture<String> getCompletedFutureResult(){
CompletableFuture<String> future
= CompletableFuture.supplyAsync(this::processRequest);
return future;
}
以及控制器中的以下端点:
@RequestMapping(path = "/asyncSupplyAsync", method = RequestMethod.GET)
public CompletableFuture<String> getValueAsyncUsingCompletableFuture() {
log.info("Request received");
CompletableFuture<String> completableFuture
= myService.getSupplyAsyncResult();
log.info("Servlet thread released");
return completableFuture;
}
和
@RequestMapping(path = "/asyncCompletable", method = RequestMethod.GET)
public CompletableFuture<String> getValueAsyncUsingCompletableFuture() {
log.info("Request received");
CompletableFuture<String> completableFuture
= myService.getCompletedFutureResult();
log.info("Servlet thread released");
return completableFuture;
}
为什么有人会在 Spring 端点的 @Async 方法中使用completableFuture.supplyAsync ? 我认为使用completableFuture.completedFuture更合适,请分享您的意见。
它们一开始就服务于完全不同的目的。 在您考虑处理一个或另一个需要多少时间之前,您可能首先想了解它们是如何工作的(无论如何,调用很少并不表示慢/快;这些数字在这种情况下没有任何意义)。
这是您拥有的相同示例:
public class SO64718973 {
public static void main(String[] args) {
System.out.println("dispatching to CF...");
//CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> processRequest());
CompletableFuture<String> future = CompletableFuture.completedFuture(processRequest());
System.out.println("done dispatching to CF...");
future.join();
}
private static String processRequest() {
System.out.println("Start processing request");
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
System.out.println("Completed processing request");
return "RESULT";
}
}
您可以运行它,然后更改实现(通过取消注释CompletableFuture.supplyAsync
)并查看System.out.println
发生的位置。 你会发现, completedFuture
将阻止main
,直到它被执行的进程,而supplyAsync
会在不同的线程中运行。 所以它不像一个是错的,一个不是,这取决于你的用例。
一般来说,使用CompletableFuture.supplyAsync
而不为其配置池并不是一个好主意; 否则它将消耗来自ForkJoinPool
线程。
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