当与重定向的自定义Http提供程序一起使用时,APP_INITIALIZER会引发"无法实例化循环依赖!ApplicationRef_"

Question

我正在使用自定义Http提供程序来处理API身份验证错误.在我的CustomHttp中,当API发出401状态错误时,我需要将用户重定向到登录页面.这很好用!

app.module.ts

export function loadCustomHttp(backend: XHRBackend, defaultOptions: AppRequestOptions,
  router: Router, dataHelper: DataHelperService) {
  return new CustomHttp(backend, defaultOptions, router, dataHelper);
}

@NgModule({
// some declarations, imports, ...
providers: [
// some services ...
 {
      provide: Http,
      useFactory: loadCustomHttp,
      deps: [XHRBackend, RequestOptions, Router, DataHelperService] 
    }
});

定制http.ts

import { Injectable } from '@angular/core';
import { Http, RequestOptions, RequestOptionsArgs, ConnectionBackend, Request, Response } from '@angular/http';
import { Router } from '@angular/router';
import { Observable } from 'rxjs/Observable';

import { DataHelperService } from '../helpers/data-helper.service';
import { AuthStorage } from '../services/auth/auth-storage';

import 'rxjs/add/observable/throw';
import 'rxjs/add/observable/empty';

@Injectable()
export class CustomHttp extends Http {
  constructor(backend: ConnectionBackend, defaultOptions: RequestOptions,
    private router: Router, private dataHelper: DataHelperService) {
    super(backend, defaultOptions);
  }


  request(url: string | Request, options?: RequestOptionsArgs): Observable<Response> {
    return this.intercept(super.request(url, options));
  }

  get(url: string, options?: RequestOptionsArgs): Observable<Response> {
    return this.intercept(super.get(url, options));
  }

  post(url: string, body: string, options?: RequestOptionsArgs): Observable<Response> {
    return this.intercept(super.post(url, body, options));
  }

  put(url: string, body: string, options?: RequestOptionsArgs): Observable<Response> {
    return this.intercept(super.put(url, body, options));
  }

  delete(url: string, options?: RequestOptionsArgs): Observable<Response> {
    return this.intercept(super.delete(url, options));
  }



  intercept(observable: Observable<Response>): Observable<Response> {
    return observable.catch((err, source) => {
      let token = AuthStorage.getToken();

      if (err.status === 401 && token && AuthStorage.isTokenExpired())    { 
        // token has expired -> redirecting user to login
        AuthStorage.clearAll();
        this.router.navigate(['auth/login']);
      }
      return Observable.throw(err);
    });
  }
}

然后,我尝试使用APP_INITIALIZERopaque标记来获取初始化我的应用程序所需的设置.

app.module.ts

@NgModule({
// some declarations, imports, ...
providers: [
// some services ...
    ConfigService,
    { 
      provide: APP_INITIALIZER, 
      useFactory: (config: ConfigService) => () => config.load(), 
      deps:[ConfigService, Http],
      multi: true
    }
});

config.service.ts

import { Injectable } from '@angular/core';
import { Http, Response } from '@angular/http';
import { AppSettings } from '../../environments/app-settings';
import { Observable } from 'rxjs/Observable';

import 'rxjs/add/operator/toPromise';

@Injectable()
export class ConfigService {

  public settings:AppSettings;

  constructor(private http:Http) { }

  load() : Promise<AppSettings> {
    let url = '/settings/';

    var observable= this.http.get(url)
            .map(res => res.json());

    observable.subscribe(config => this.settings = config);
    return observable.toPromise();
  }

}

这会产生错误:

Uncaught Error: Provider parse errors:
Cannot instantiate cyclic dependency! ApplicationRef_: in NgModule AppModuleNgModuleProviderAnalyzer.parse @ provider_analyzer.js:291NgModuleCompiler.compile @ ng_module_compiler.js:54RuntimeCompiler._compileModule @ runtime_compiler.js:102RuntimeCompiler._compileModuleAndComponents @ runtime_compiler.js:65RuntimeCompiler.compileModuleAsync @ runtime_compiler.js:55PlatformRef_._bootstrapModuleWithZone @ application_ref.js:303PlatformRef_.bootstrapModule @ application_ref.js:285(anonymous function) @ main.ts:18__webpack_require__ @ bootstrap 0e2b412…:52(anonymous function) @ main.bundle.js:86665__webpack_require__ @ bootstrap 0e2b412…:52webpackJsonpCallback @ bootstrap 0e2b412…:23(anonymous function) @ main.bundle.js:1

如果我注释掉自定义Http提供程序,则不会显示错误,并且APP_INITIALIZER按预期工作.如果我Router从Http提供程序deps声明中删除,我不再有错误,但我的ConfigService.load()函数被调用两次.

有谁知道为什么这个路由器依赖导致这种循环依赖性错误？如何防止我的ConfigService.load()函数被调用两次？

如果需要,我创建了一个公共存储库来重现错误:https://github.com/haia212/AngularErrorTestProject

Answer 1

问题是Router可以异步加载一些路由.这就是它需要的原因Http.你的Http依赖Router和Router依赖Http.角度注入器无法创建任何这些服务.

我有类似的问题,其中一个解决方案可能是注入Injector而不是服务,然后获得服务.

码:

@Injectable()
export class CustomHttp extends Http {
  constructor(backend: ConnectionBackend, defaultOptions: RequestOptions,
    private injector: Injector, private dataHelper: DataHelperService) {
    super(backend, defaultOptions);
  }

  public get router(): Router { //this creates router property on your service.
     return this.injector.get(Router);
  }
  ...

所以,基本上,你不需要Router获得Http服务实例.router只有当您想要重定向用户时,才会在访问属性时完成注入.router属性对代码的其他部分是透明的.

如果它不能解决问题,您可以对其余注入的服务执行相同的操作(除了要调用的服务super).