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本篇文章带大家了解一下Angular中的HttpClientModule模块，介绍一下HttpClientModule模块的使用方法，希望对大家有所帮助！

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。【相关教程推荐：《angular教程》】

1. 快速开始

引入 HttpClientModule 模块

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

注入 HttpClient 服务实例对象，用于发送请求

// app.component.tsimport { HttpClient } from '@angular/common/http';export class AppComponent {  constructor(private http: HttpClient) {}}

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")  }}

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]);

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

3. 请求参数

HttpParams 类

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 接口

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

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"})

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;}

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

5. 响应内容

// app.component.tsimport { HttpClient } from '@angular/common/http';export class AppComponent {  constructor(private http: HttpClient) {}}0

// app.component.tsimport { HttpClient } from '@angular/common/http';export class AppComponent {  constructor(private http: HttpClient) {}}1

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。（Token、Error）

拦截器将只拦截使用 HttpClientModule 模块发出的请求。

// app.component.tsimport { HttpClient } from '@angular/common/http';export class AppComponent {  constructor(private http: HttpClient) {}}2

6.1 请求拦截

// app.component.tsimport { HttpClient } from '@angular/common/http';export class AppComponent {  constructor(private http: HttpClient) {}}3

6.2 响应拦截

// app.component.tsimport { HttpClient } from '@angular/common/http';export class AppComponent {  constructor(private http: HttpClient) {}}4

6.3 拦截器注入

// app.component.tsimport { HttpClient } from '@angular/common/http';export class AppComponent {  constructor(private http: HttpClient) {}}5

7. Angular Proxy

在项目的根目录下创建 proxy.conf.JSon 文件并加入如下代码

// app.component.tsimport { HttpClient } from '@angular/common/http';export class AppComponent {  constructor(private http: HttpClient) {}}6

/api/：在应用中发出的以 /api 开头的请求走此代理

target：服务器端 URL

secure：如果服务器端 URL 的协议是 https，此项需要为 true

changeOrigin：如果服务器端不是 localhost， 此项需要为 true

指定 proxy 配置文件 (方式一)

// app.component.tsimport { HttpClient } from '@angular/common/http';export class AppComponent {  constructor(private http: HttpClient) {}}7

指定 proxy 配置文件 (方式二)

// app.component.tsimport { HttpClient } from '@angular/common/http';export class AppComponent {  constructor(private http: HttpClient) {}}8

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