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_INITIALIZER不透明令牌来获取初始化我的应用所需的设置。

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，APP_INITIALIZER按预期工作。如果我从Http提供程序deps声明中删除Router，我不再有错误，但我的ConfigService.load()函数被调用了两次。

有谁知道为什么这个路由器依赖会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可以异步加载某些路由。这就是它需要Http的原因。您的Http取决于Router，Router取决于Http。角度注入器无法创建任何这些服务。

我遇到了类似的问题，其中一个解决方案可能是注入Injector而不是服务并在之后获得服务。

代码：

@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);
  }
  ...

因此，基本上，您不需要Router来获取Http服务的实例。只有当您想要重定向用户时，才会在访问router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，你可以对其他注入的服务做同样的事情（除了调用super之外）。

Answer 2

也许这会有所帮助;我解决这个问题的方法是改变CustomHttp类的策略，改为使用合成。

我的CustomHttp看起来像这样：

@Injectable()
export class CustomHttp {

    constructor(private http: Http) {}

现在，我不需要在我的自定义Http服务中注入路由器或任何其他服务。

在配置加载程序（config.service.ts）中，我做了以下更改：

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() { }

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

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

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

}

删除了注入Http服务依赖项的需要，而是将其添加到load(http: Http)方法。

在我app.module.ts我有以下内容：

providers: [
    {
        provide: Http,
        useFactory: (backend, options) => new CustomHttp(new Http(backend, options)),
        deps: [XHRBackend, RequestOptions]
    },
    ConfigService,
    {
        provide: APP_INITIALIZER,
        useFactory: (config, http) => () => config.load(http),
        deps: [ConfigService, Http],
        multi: true
    },

这就是我目前在我的应用上使用的内容。不确定这种方法是否适合您，但希望它有所帮助。

Answer 3

我只是通过从deps声明中删除路由器来解决它：

{
      provide: Http,
      useFactory: loadCustomHttp,
      deps: [XHRBackend, RequestOptions, DataHelperService]
    }

其他一切都保持不变。感觉有点像魔术，但它有效。

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_”

3 个答案: