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HttpClientModule

该模块用于发送 Http 请求,用于发送请求的方法都返回 Observable 对象。

1. 快速开始

  1. 引入 HttpClientModule 模块

    // app.module.ts
    import { httpClientModule } from '@angular/common/http';
    imports: [
      httpClientModule
    ]
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  2. 注入 HttpClient 服务实例对象,用于发送请求

    // app.component.ts
    import { HttpClient } from '@angular/common/http';
    
    export class AppComponent {
      constructor(private http: HttpClient) {}
    }
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  3. 发送请求

    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")
      }
    }
    复制代码

2. 请求方法

this.http.get(url [, options]);
this.http.post(url, data [, options]);
this.http.delete(url [, options]);
this.http.put(url, data [, options]);
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this.http.get<Post[]>('/getAllPosts')
  .subscribe(response => console.log(response))
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3. 请求参数

  1. HttpParams

    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;
    }
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  2. HttpParamsOptions 接口

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

    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"})
    复制代码

4. 请求头

请求头字段的创建需要使用 HttpHeaders 类,在类实例对象下面有各种操作请求头的方法。

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;
}
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let headers = new HttpHeaders({ test: "Hello" })
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5. 响应内容

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

拦截器是 Angular 应用中全局捕获和修改 HTTP 请求和响应的方式。(TokenError

拦截器将只拦截使用 HttpClientModule 模块发出的请求。

$ ng g interceptor <name>
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6.1 请求拦截

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  constructor() {}
  // 拦截方法
  intercept(
    // unknown 指定请求体 (body) 的类型
    request: HttpRequest<unknown>,
    next: HttpHandler
     // unknown 指定响应内容 (body) 的类型
  ): Observable<HttpEvent<unknown>> {
    // 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)
  }
}
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6.2 响应拦截

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

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

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

  1. 在项目的根目录下创建 proxy.conf.json 文件并加入如下代码

    {
         "/api/*": {
            "target": "http://localhost:3070",
            "secure": false,
            "changeOrigin": true
          }
    }
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    1. /api/:在应用中发出的以 /api 开头的请求走此代理
    2. target:服务器端 URL
    3. secure:如果服务器端 URL 的协议是 https,此项需要为 true
    4. changeOrigin:如果服务器端不是 localhost, 此项需要为 true
  2. 指定 proxy 配置文件 (方式一)

    // package.json
    "scripts": {
      "start": "ng serve --proxy-config proxy.conf.json",
    }
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  3. 指定 proxy 配置文件 (方式二)

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