Angular Spring Boot 2 Reactor Flux 的客户端 API

Question

如何为 Java Project Reactor 反应式 Flux API 创建一个 Angular 4 客户端？下面的示例有两个 API：一个 Mono API；并且，Flux API。两者都来自 curl；但在 Angular 4 (4.1.2) 中只有 Mono API 有效；任何想法如何让 Angular 4 与 Flux API 一起工作？

这是一个简单的 Spring Boot 2.0.0-SNAPSHOT 应用程序，带有 Mono API 和 Flux API:

@SpringBootApplication
@RestController
public class ReactiveServiceApplication {

    @CrossOrigin
    @GetMapping("/events/{id}")
    public Mono<Event> eventById(@PathVariable long id) {
        return Mono.just(new Event(id, LocalDate.now()));
    }

    @CrossOrigin
    @GetMapping(value = "/events", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
    public Flux<Event> events() {
        Flux<Event> eventFlux = Flux.fromStream(
            Stream.generate(
                ()->new Event(System.currentTimeMillis(), LocalDate.now()))
            );

        Flux<Long> durationFlux = Flux.interval(Duration.ofSeconds(1));

        return Flux.zip(eventFlux, durationFlux).map(Tuple2::getT1);
    }

    public static void main(String[] args) {
        SpringApplication.run(ReactiveServiceApplication.class);
    }
}

使用 Lombok 事件：

@Data
@AllArgsConstructor
public class Event {
    private final long id;
    private final LocalDate when;
}

这些反应性 API 如我所料，通过 curl 工作：

jan@linux-6o1s:~/src> curl -s http://localhost:8080/events/123
{"id":123,"when":{"year":2017,"month":"MAY","monthValue":5,"dayOfMonth":15,"dayOfWeek":"MONDAY","era":"CE","dayOfYear":135,"leapYear":false,"chronology":{"calendarType":"iso8601","id":"ISO"}}}

与非终止 Flux 类似 API:

jan@linux-6o1s:~/src> curl -s http://localhost:8080/events
data:{"id":1494887783347,"when":{"year":2017,"month":"MAY","monthValue":5,"dayOfMonth":15,"dayOfWeek":"MONDAY","era":"CE","dayOfYear":135,"leapYear":false,"chronology":{"calendarType":"iso8601","id":"ISO"}}}

data:{"id":1494887784348,"when":{"year":2017,"month":"MAY","monthValue":5,"dayOfMonth":15,"dayOfWeek":"MONDAY","era":"CE","dayOfYear":135,"leapYear":false,"chronology":{"calendarType":"iso8601","id":"ISO"}}}

data:{"id":1494887785347,"when":{"year":2017,"month":"MAY","monthValue":5,"dayOfMonth":15,"dayOfWeek":"MONDAY","era":"CE","dayOfYear":135,"leapYear":false,"chronology":{"calendarType":"iso8601","id":"ISO"}}}

...

同样琐碎的 Angular 4 客户端与 RxJS：

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent  implements OnInit, OnDestroy {
  title = 'app works!';
  event: Observable<Event>;
  subscription: Subscription;

  constructor(
    private _http: Http
    ) {
  }

  ngOnInit() {
    this.subscription = this._http
      .get("http://localhost:8080/events/322")
      .map(response => response.json())
      .subscribe(
        e => { 
          this.event = e;
        }
      );
  }

  ngOnDestroy() {
    this.subscription.unsubscribe();
  }
}

适用于 Mono API:

"http://localhost:8080/events/322"

但是 Flux API:

"http://localhost:8080/events"

从不触发事件处理程序，不像 curl。

Answer 1

这里猜测 /events 的 url 是问题所在，因为它应该产生 json 来处理。

@SpringBootApplication
@RestController
public class ReactiveServiceApplication {

    @CrossOrigin
    @GetMapping("/events/{id}")
    public Mono<Event> eventById(@PathVariable long id) {
        return Mono.just(new Event(id, LocalDate.now()));
    }

    @CrossOrigin
    @GetMapping(value = "/events", produces = MediaType.APPLICATION_JSON_VALUE)
    public Flux<Event> events() {
        Flux<Event> eventFlux = Flux.fromStream(
            Stream.generate(
                ()->new Event(System.currentTimeMillis(), LocalDate.now()))
            );

        Flux<Long> durationFlux = Flux.interval(Duration.ofSeconds(1));

        return Flux.zip(eventFlux, durationFlux).map(Tuple2::getT1);
    }

    public static void main(String[] args) {
        SpringApplication.run(ReactiveServiceApplication.class);
    }
}

Answer 2

基于 Flux 的控制器正在生成服务器发送事件 (SSE)。我认为来自 Angular2 的 Http 客户端不允许您使用 SSE...

编辑：看起来 EventSource 是你需要的，看到这个类似 question/answer：

Answer 3

这是一个有效的 Angular 4 SSE 示例，正如 Simon 在他的回答中所描述的那样。这花了一些时间拼凑起来，所以也许对其他人有用。这里的关键部分是区域——没有区域，SSE 更新将不会触发 Angular 的变更检测。

import { Component, NgZone, OnInit, OnDestroy } from '@angular/core';
import { Http } from '@angular/http';
import { Observable } from 'rxjs/Observable';
import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import { Subscription } from 'rxjs/Subscription';
import 'rxjs/add/operator/map';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent  implements OnInit {
  event: Observable<MyEvent>;
  private _eventSource: EventSource;
  private _events: BehaviorSubject<MyEvent> = new BehaviorSubject<MyEvent>(null);
  constructor(private _http: Http, private _zone: NgZone) {}
  ngOnInit() {
    this._eventSource = this.createEventSource();
    this.event = this.createEventObservable();
  }

  private createEventObservable(): Observable<MyEvent> {
    return this._events.asObservable();
  }

  private createEventSource(): EventSource {
      const eventSource = new EventSource('http://localhost:8080/events');
      eventSource.onmessage = sse => {
        const event: MyEvent = new MyEvent(JSON.parse(sse.data));
        this._zone.run(()=>this._events.next(event));
      };
      eventSource.onerror = err => this._events.error(err);
      return eventSource;
  }
}

对应的HTML就是：

<b>Observable of sse</b>
<div *ngIf="(event | async); let evt; else loading">
  <div>ID: {{evt.id}} </div>
</div>
<ng-template #loading>Waiting...</ng-template>

事件很简单：

export class MyEvent {
  id: number;
  when: any;

  constructor(jsonData) {
    Object.assign(this, jsonData);
  }
}

并且由于我的 TS 不包括 EventSource 或 Callback，我将它们存根于：

interface Callback { (data: any): void; }

declare class EventSource {
    onmessage: Callback;
    onerror: Callback;
    addEventListener(event: string, cb: Callback): void;
    constructor(name: string);
    close: () => void;
}

Angular Spring Boot 2 Reactor Flux 的客户端 API

Angular client of Spring Boot 2 Reactor Flux API

java

angular

rxjs5

angular-http

project-reactor