淺析Angular中HttpClientModule模組有什麼用？怎麼用？

本篇文章帶大家了解一下Angular中的HttpClientModule模組，介紹一下HttpClientModule模組的使用方法，希望對大家有幫助！

該模組用於發送 Http 請求，用於發送請求的方法都會傳回 Observable 物件。 【相關教學推薦：《angular教學》】

1.  快速開始

介紹HttpClientModule 模組

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

注入HttpClient 服務實例對象，用於發送請求

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

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

發送請求

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('/getAllPosts')
  .subscribe(response => console.log(response))

3.  請求參數

HttpParams 類別

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;
}

HttpParamsOptions 介面

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

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，在類別實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.  回應內容

#

declare type HttpObserve = 'body' | 'response';
// response 读取完整响应体
// body 读取服务器端返回的数据

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

##6.  攔截器

#攔截器是

Angular 應用程式中全域擷取和修改HTTP 請求和回應的方式。 （Token、Error）

攔截器將只攔截使用

HttpClientModule 模組發出的請求。

$ ng g interceptor 

6.1  請求攔截

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  constructor() {}
  // 拦截方法
  intercept(
    // unknown 指定请求体 (body) 的类型
    request: HttpRequest,
    next: HttpHandler
     // unknown 指定响应内容 (body) 的类型
  ): Observable> {
    // 克隆并修改请求头
    const req = request.clone({
      setHeaders: {
        Authorization: "Bearer xxxxxxx"
      }
    })
    // 通过回调函数将修改后的请求头回传给应用
    return next.handle(req)
  }
}

6.2  回應攔截

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  constructor() {}
  // 拦截方法
  intercept(
    request: HttpRequest,
    next: HttpHandler
  ): Observable {
    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

#在專案的根目錄下建立 

proxy.conf.json 檔案並加入以下程式碼

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

• /api/：在應用程式中發出的以/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，此項目需要為true

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

#指定

proxy 設定檔(方式一)

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

指定

proxy 設定檔(方式二)

// angular.json 文件中
"serve": {
  "options": {
    "proxyConfig": "proxy.conf.json"
  },

更多程式相關知識，請造訪：

程式設計入門！ ！

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