RxJava 和 Spring MVC （译）
RxJava with Spring MVC
Spring Cloud Netflix引入了Rxjava
RxJava是一个Reactive Extensions的Java VM实现:它是一个使用可观察数据流进行异步编程的编程接口，ReactiveX结合了观察者模式、迭代器模式和函数式编程的精华，与异步数据流交互的编程范式。
Spring Cloud Netflix提供并支持从Spring MVC Controllers返回rx.Single对象. 它还支持使用 rx.Observable 对象，可观察的对象为 Server-sent events (SSE). 如果你的内部api已经使用RxJava这会非常的方便(可以查看spring-cloud-feign-hystrix为例)。
这里有一些使用rx.Single的列子：
@RequestMapping(method = RequestMethod.GET, value = "/single")
public Single single() {
return Single.just("single value");
}
@RequestMapping(method = RequestMethod.GET, value = "/singleWithResponse")
public ResponseEntity> singleWithResponse() {
return new ResponseEntity<>(Single.just("single value"),
HttpStatus.NOT_FOUND);
}
@RequestMapping(method = RequestMethod.GET, value = "/singleCreatedWithResponse")
public Single> singleOuterWithResponse() {
return Single.just(new ResponseEntity<>("single value", HttpStatus.CREATED));
}
@RequestMapping(method = RequestMethod.GET, value = "/throw")
public Single 如果你使用 Observable, 而不Single, 你可以使用.toSingle() 或 .toList().toSingle(). 下面是些例子:
@RequestMapping(method = RequestMethod.GET, value = "/single")
public Single single() {
return Observable.just("single value").toSingle();
}
@RequestMapping(method = RequestMethod.GET, value = "/multiple")
public Single> multiple() {
return Observable.just("multiple", "values").toList().toSingle();
}
@RequestMapping(method = RequestMethod.GET, value = "/responseWithObservable")
public ResponseEntity> responseWithObservable() {
Observable observable = Observable.just("single value");
HttpHeaders headers = new HttpHeaders();
headers.setContentType(APPLICATION_JSON_UTF8);
return new ResponseEntity<>(observable.toSingle(), headers, HttpStatus.CREATED);
}
@RequestMapping(method = RequestMethod.GET, value = "/timeout")
public Observable timeout() {
return Observable.timer(1, TimeUnit.MINUTES).map(new Func1() {
@Override
public String call(Long aLong) {
return "single value";
}
});
}
如果你有一个流端点和客户端,SSE可能是一个选项。使用 RxResponse.sse()将rx.Observable转换到Spring 的SseEmitter. 以下是一些例子:
@RequestMapping(method = RequestMethod.GET, value = "/sse")
public SseEmitter single() {
return RxResponse.sse(Observable.just("single value"));
}
@RequestMapping(method = RequestMethod.GET, value = "/messages")
public SseEmitter messages() {
return RxResponse.sse(Observable.just("message 1", "message 2", "message 3"));
}
@RequestMapping(method = RequestMethod.GET, value = "/events")
public SseEmitter event() {
return RxResponse.sse(APPLICATION_JSON_UTF8,
Observable.just(new EventDto("Spring io", getDate(2016, 5, 19)),
new EventDto("SpringOnePlatform", getDate(2016, 8, 1))));
}