对于Angular 5及以上版本，我们可以使用HttpInterceptor泛化请求和响应操作。 这有助于我们避免重复:

1)通用报头

2)指定响应类型

3)查询请求

import { Injectable } from '@angular/core';
import {
  HttpRequest,
  HttpHandler,
  HttpEvent,
  HttpInterceptor,
  HttpResponse,
  HttpErrorResponse
} from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/do';

@Injectable()
export class AuthHttpInterceptor implements HttpInterceptor {

  requestCounter: number = 0;
  constructor() {
  }

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

    request = request.clone({
      responseType: 'json',
      setHeaders: {
        Authorization: `Bearer token_value`,
        'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8'
      }
    });

    return next.handle(request).do((event: HttpEvent<any>) => {
      if (event instanceof HttpResponse) {
        // do stuff with response if you want
      }
    }, (err: any) => {
      if (err instanceof HttpErrorResponse) {
        // do stuff with response error if you want
      }
    });
  }
}

我们可以使用这个AuthHttpInterceptor类作为HttpInterceptors的提供者:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
import { AppRoutingModule } from './app.routing-module';
import { AuthHttpInterceptor } from './services/auth-http.interceptor';
import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    HttpClientModule,
    BrowserAnimationsModule,
  ],
  providers: [
    {
      provide: HTTP_INTERCEPTORS,
      useClass: AuthHttpInterceptor,
      multi: true
    }
  ],
  exports: [],
  bootstrap: [AppComponent]
})
export class AppModule {
}

像下面这样保持独立的服务怎么样

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


            @Injectable()
            export class HttpClientService extends RequestOptions {

                constructor(private requestOptionArgs:RequestOptions) {
                    super();     
                }

                addHeader(headerName: string, headerValue: string ){
                    (this.requestOptionArgs.headers as Headers).set(headerName, headerValue);
                }
            }

当你从另一个地方调用这个时，使用this. httpclientservice。addHeader("Authorization"， " holder " + this.tok);

您将看到添加的标题，例如:-授权如下

虽然我很晚才回，但也许能帮到别人。当使用@NgModule时，要向所有请求注入头文件，可以这样做:

(我在Angular 2.0.1中进行了测试)

/**
 * Extending BaseRequestOptions to inject common headers to all requests.
 */
class CustomRequestOptions extends BaseRequestOptions {
    constructor() {
        super();
        this.headers.append('Authorization', 'my-token');
        this.headers.append('foo', 'bar');
    }
}

现在在@NgModule中执行以下操作:

@NgModule({
    declarations: [FooComponent],
    imports     : [

        // Angular modules
        BrowserModule,
        HttpModule,         // This is required

        /* other modules */
    ],
    providers   : [
        {provide: LocationStrategy, useClass: HashLocationStrategy},
        // This is the main part. We are telling Angular to provide an instance of
        // CustomRequestOptions whenever someone injects RequestOptions
        {provide: RequestOptions, useClass: CustomRequestOptions}
    ],
    bootstrap   : [AppComponent]
})

我设置头的最大问题(在2022年)是HttpHeaders上的append方法返回原始对象的克隆，而没有修改原始对象本身。所以标题。Append ('header'， 'value')不够。我必须重新分配结果或直接在HTTP调用中使用它:

let headers = new HttpHeaders();
headers = headers.append('header', 'value');
this.http.get<any>('https://someulr.com/api/users', { headers });

从Angular 4.3开始，HTTP拦截器现在可以通过新的HttpClient @angular/common/ HTTP使用了。X版本及更高版本。

现在为每个请求添加头文件非常简单:

import {
  HttpEvent,
  HttpInterceptor,
  HttpHandler,
  HttpRequest,
} from '@angular/common/http';
import { Observable } from 'rxjs';
import { Injectable } from '@angular/core';

@Injectable()
export class AddHeaderInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    // Clone the request to add the new header
    const clonedRequest = req.clone({ headers: req.headers.append('Authorization', 'Bearer 123') });

    // Pass the cloned request instead of the original request to the next handle
    return next.handle(clonedRequest);
  }
}

有一个不可变性的原则，这就是为什么在设置新内容之前需要克隆请求。

由于编辑头部是一个非常常见的任务，实际上有一个快捷方式(在克隆请求时):

const clonedRequest = req.clone({ setHeaders: { Authorization: 'Bearer 123' } });

创建拦截器之后，你应该使用HTTP_INTERCEPTORS提供的方法注册它。

import { HTTP_INTERCEPTORS } from '@angular/common/http';

@NgModule({
  providers: [{
    provide: HTTP_INTERCEPTORS,
    useClass: AddHeaderInterceptor,
    multi: true,
  }],
})
export class AppModule {}

const headers = new HttpHeaders()
  .set('content-type', 'application/json')
  .set('x-functions-key', '');

return this.http.get<Person[]>(baseUrl, {
      headers: headers,
    });

使用append方法将新值附加到现有值集

headers.append('Access-Control-Allow-Origin', '*')