Angular 4.3拦截器 - 如何使用?

时间:2017-07-27 16:00:27

标签: angular typescript angular-http angular-http-interceptors

我正在构建一个需要授权标头的新应用。通常我会使用与此scotch.io article中的方法非常相似的内容。但是我注意到,现在通过新的HttpClientModule在Angular 4生态系统中完全支持HTTP拦截器,我正在尝试找到一些关于如何使用它们的文档。

如果我不正确(从4.3开始)这是注入授权标题的最佳做法,我也愿意接受建议。我的想法是,它是最近添加的一个功能,这意味着可能有充分的理由迁移到" Angular Approved"方法

3 个答案:

答案 0 :(得分:9)

这个答案借鉴了CodeWarrior链接的official documentation

Angular允许您创建HttpInterceptor:

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

@Injectable()
export class NoopInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(req);
  }
}

然后您可以将其集成到您的应用中:

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

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

要添加授权标头,您可以使用更改的标头克隆请求:

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

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  constructor(private auth: AuthService) {}

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    // Get the auth header from the service.
    const authHeader = this.auth.getAuthorizationHeader();
    // Clone the request to add the new header.
    const authReq = req.clone({headers: req.headers.set('Authorization', authHeader)});
    // Pass on the cloned request instead of the original request.
    return next.handle(authReq);
  }
}

请注意,拦截器的作用类似于链,因此您可以设置多个拦截器来执行不同的任务。

答案 1 :(得分:3)

向Interceptor的构造函数注入AuthService给了我这个错误:

  

未捕获错误:提供程序解析错误:无法实例化循环   依赖! InjectionToken_HTTP_INTERCEPTORS(&#34; [ERROR - &gt;]&#34;):in   NgModule AppModule在./AppModule@-1:-1

所以我没有将它注入构造函数,而是使用了Injector的{​​{1}}而且工作正常。我将令牌存储在@angular/core并使用基本身份验证。我需要设置

localStorage

以下是我的实施方式:

<强> token.interceptor.ts

Authorization: 'Bearer token_string'

AuthService中的getToken函数

在这里,您可以实现整个逻辑来获取标头或仅获取标记。在我的情况下,我只是调用它来获取JWT标记字符串。

import {Injectable, Injector} from '@angular/core';

import { HttpRequest, HttpHandler, HttpEvent, HttpInterceptor } from '@angular/common/http';
import {Observable} from 'rxjs/Observable';
import {AuthService} from './auth.service';

@Injectable()
export class TokenInterceptor implements HttpInterceptor {

    constructor(private injector: Injector) { }

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

        const auth = this.injector.get(AuthService);
        if (auth.getToken()) {
            request = request.clone({
                setHeaders: {
                    Authorization: `Bearer ${auth.getToken()}`
                }
            });

        }

        return next.handle(request);
    }
}

<强> app.module.ts

导入/** * Get jwt token * @returns {string} */ getToken(): string { return localStorage.getItem('token'); }

TokenInterceptor

import {TokenInterceptor} from './pathToTheFile/token.interceptor'; 数组中的@NgModule下添加以下内容。

providers:

答案 2 :(得分:0)

我推荐的方法存在的问题是,拦截器必须在编译时就知道,而且显然所有这些都在同一模块中。

我选择实现一个拦截器和一系列处理程序功能,这些功能可以在运行时扩展。服务的拦截方法会处理next()逻辑。

服务(基本代码,无验证或维护):

export type HttpHandlerFunction = (req: HttpRequest<any>) => HttpRequest<any>;

@Injectable()
export class HttpInterceptorService implements HttpInterceptor {
    private _handlers: Array<HttpHandlerFunction> = [];

    addHandler(handler: HttpHandlerFunction): void {
        this._handlers.push(handler);
    }

    intercept(req: HttpRequest<any>, next: HttpHandler):
        Observable<HttpEvent<any>> {
            this._handlers.forEach((handler: HttpHandlerFunction) => {
                req = handler(req);
            })
        return next.handle(req);
    }
}

以及用法,在不同模块中的某些服务中:

constructor(injector: Injector) {

    const interceptorsArray: Array<any> = injector.get(HTTP_INTERCEPTORS),
        interceptor: HttpInterceptorService = interceptorsArray &&
            interceptorsArray.filter((i: any) => i instanceof HttpInterceptorService)[0];
    if (interceptor) {
        interceptor.addHandler((req: HttpRequest<any>) => {
            const accessToken = this.getAccessToken();
            if (accessToken) {
                // doesn't work with direct headers.set, you must clone
                req = req.clone({ headers: req.headers.set('Authorization', accessToken) });
            }
        return req;
    });
}