angular學習之淺析HttpClientModule模組

該模組用於傳送 Http 請求，用於傳送請求的方法都返回 Observable 物件。【相關教學推薦：《》】

1、快速開始

1）、引入 HttpClientModule 模組

// app.module.ts
import { httpClientModule } from '@angular/common/http';
imports: [
  httpClientModule
]

2）、注入 HttpClient 服務範例物件，用於傳送請求

// app.component.ts
import { HttpClient } from '@angular/common/http';

export class AppComponent {
	constructor(private http: HttpClient) {}
}

3）、傳送請求

import { HttpClient } from "@angular/common/http"

export class AppComponent implements OnInit {
  constructor(private http: HttpClient) {}
  ngOnInit() {
    this.getUsers().subscribe(console.log)
  }
  getUsers() {
    return this.http.get("https://jsonplaceholder.typicode.com/users")
  }
}

2、請求方法

this.http.get(url [, options]);
this.http.post(url, data [, options]);
this.http.delete(url [, options]);
this.http.put(url, data [, options]);

this.http.get<Post[]>('/getAllPosts')
  .subscribe(response => console.log(response))

3、請求引數

1、HttpParams 類

export declare class HttpParams {
    constructor(options?: HttpParamsOptions);
    has(param: string): boolean;
    get(param: string): string | null;
    getAll(param: string): string[] | null;
    keys(): string[];
    append(param: string, value: string): HttpParams;
    set(param: string, value: string): HttpParams;
    delete(param: string, value?: string): HttpParams;
    toString(): string;
}

2、HttpParamsOptions 介面

declare interface HttpParamsOptions {
    fromString?: string;
    fromObject?: {
        [param: string]: string | ReadonlyArray<string>;
    };
    encoder?: HttpParameterCodec;
}

3、使用範例

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

let params = new HttpParams({ fromObject: {name: "zhangsan", age: "20"}})
params = params.append("sex", "male")
let params = new HttpParams({ fromString: "name=zhangsan&age=20"})

4、請求頭

請求頭欄位的建立需要使用 HttpHeaders 類，在類範例物件下面有各種操作請求頭的方法。

export declare class HttpHeaders {
    constructor(headers?: string | {
        [name: string]: string | string[];
    });
    has(name: string): boolean;
    get(name: string): string | null;
    keys(): string[];
    getAll(name: string): string[] | null;
    append(name: string, value: string | string[]): HttpHeaders;
    set(name: string, value: string | string[]): HttpHeaders;
    delete(name: string, value?: string | string[]): HttpHeaders;
}

let headers = new HttpHeaders({ test: "Hello" })

5、響應內容

declare type HttpObserve = 'body' | 'response';
// response 讀取完整響應體
// body 讀取伺服器端返回的資料

this.http.get(
  "https://jsonplaceholder.typicode.com/users", 
  { observe: "body" }
).subscribe(console.log)

6、攔截器

攔截器是 Angular 應用中全域性捕獲和修改 HTTP 請求和響應的方式。（Token、Error）

攔截器將只攔截使用 HttpClientModule 模組發出的請求。

ng g interceptor <name>

6.1 請求攔截

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  constructor() {}
	// 攔截方法
  intercept(
  	// unknown 指定請求體 (body) 的型別
    request: HttpRequest<unknown>,
    next: HttpHandler
     // unknown 指定響應內容 (body) 的型別
  ): Observable<HttpEvent<unknown>> {
    // 克隆並修改請求頭
    const req = request.clone({
      setHeaders: {
        Authorization: "Bearer xxxxxxx"
      }
    })
    // 通過回撥函數將修改後的請求頭回傳給應用
    return next.handle(req)
  }
}

6.2 響應攔截

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  constructor() {}
	// 攔截方法
  intercept(
    request: HttpRequest<unknown>,
    next: HttpHandler
  ): Observable<any> {
    return next.handle(request).pipe(
      retry(2),
      catchError((error: HttpErrorResponse) => throwError(error))
    )
  }
}

6.3 攔截器注入

import { AuthInterceptor } from "./auth.interceptor"
import { HTTP_INTERCEPTORS } from "@angular/common/http"

@NgModule({
  providers: [
    {
      provide: HTTP_INTERCEPTORS,
      useClass: AuthInterceptor,
      multi: true
    }
  ]
})

7、Angular Proxy

1、在專案的根目錄下建立 proxy.conf.json 檔案並加入如下程式碼

{
 	"/api/*": {
    "target": "http://localhost:3070",
    "secure": false,
    "changeOrigin": true
  }
}

• /api/*：在應用中發出的以 /api 開頭的請求走此代理

• target：伺服器端 URL

• secure：如果伺服器端 URL 的協定是 https，此項需要為 true

• changeOrigin：如果伺服器端不是 localhost， 此項需要為 true

2、指定 proxy 組態檔 (方式一)

"scripts": {
  "start": "ng serve --proxy-config proxy.conf.json",
}

3、指定 proxy 組態檔 (方式二)

"serve": {
  "options": {
    "proxyConfig": "proxy.conf.json"
  },

該模組用於傳送 Http 請求，用於傳送請求的方法都返回 Observable 物件。

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