Rxjava Single-控制器无响应

Question

我正在使用RxJava异步调用第三方Web服务API。我正在使用Single创建可观察的。在运行代码时，我发现控制器返回的ReponseEntity类型很好，但是，当我将其更改为Single时，控制器不会返回响应，并且请求将永远等待。这是代码块：

Configurations: rxjava2, SpringBoot 2.0.6.RELEASE, rxjava-reactive-streams 1.2.1

Works：

//RxJava
@GetMapping(value = "/getBook/{bookNumber}", produces = "application/json")
public ResponseEntity<String> getBookAsync(@PathVariable(value = "bookNumber") 
String bookNumber, @RequestHeader(name = ConstantsUtility.CORRELATION_ID, 
required = true) final String correlationId) {

return new ResponseEntity<>("single value", HttpStatus.CREATED);

    }

无响应，请求永远等待

//RxJava
@GetMapping(value = "/getBook/{bookNumber}", produces = "application/json")
 public Single<ResponseEntity<String>> getBookAsync(@PathVariable(
value = "bookNumber") 
String bookNumber, @RequestHeader(name = ConstantsUtility.CORRELATION_ID, required = true) final String correlationId){

        return Single.just(new ResponseEntity<>("single value", HttpStatus.CREATED));

    }

对此表示感谢！ 谢谢