Angular 2 HTTP响应拦截器

Question

在Angular 1中，全局处理HTTP响应状态是通过$httpProvider完成的：

angular.module('app', [])
    .service('httpResponseInterceptor', ['$q', function ($q) {
        this.response = function (response) {
            if (response.status === 418) {
                // do some stuff here
            }
            return response || $q.when(response);
        };
        this.responseError = function (response) {
            if (response.status === 418) {
                // do some stuff here
            }
            return $q.reject(response);
        };
    }])
    .config(['$httpProvider', function ($httpProvider) {
        // do routing, etc.

        $httpProvider.interceptors.push('httpResponseInterceptor');
    }]);

在Angular 2中，完成了对Http这样的扩展：

import { Injectable } from '@angular/core';
import {
    Http,
    Response,
    Request,
    RequestOptions,
    RequestOptionsArgs,
    XHRBackend
} from '@angular/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/throw';
import 'rxjs/add/operator/catch';

@Injectable()
export class HttpInterceptor extends Http {

  constructor(xhrBackend: XHRBackend, requestOptions: RequestOptions) {
    super(xhrBackend, requestOptions);
  }

  private catchErrors() {
    return (response: Response) => {
      if (response.status === 418) {
            // do some stuff here
      }
      return Observable.throw(response);
    };
  }

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

...并将其包含在app.module.ts ：

providers: [
    { provide: Http, useClass: HttpInterceptor }
]

请参阅此stackoverflow答案和要点以供参考。

---

但是，上面的Angular 2代码出现此错误：

无法实例化循环依赖！ Http：在NgModule AppModule中

Answer 1

这个配置对我有用。 我正在使用Angular 2 v2.4.1：

app.module.ts

{
    provide: Http,
    useFactory: (backend: XHRBackend, options: RequestOptions) => {
        return new HttpInterceptor(backend, options);
    },
    deps: [XHRBackend, RequestOptions]
}

HttpInterceptor.ts

import { Injectable } from '@angular/core';
import {
    Http,
    ConnectionBackend,
    RequestOptions,
    RequestOptionsArgs,
    Request,
    Response,
    Headers
} from '@angular/http';

import { Observable } from 'rxjs/Rx';

@Injectable()
export class HttpInterceptor extends Http {
    constructor(backend: ConnectionBackend, defaultOptions: RequestOptions) {
        super(backend, defaultOptions);
    }

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

   ...
}