在Angular HttpClient中捕获错误

我有一个如下所示的数据服务:

@Injectable()
export class DataService {
    baseUrl = 'http://localhost'
        constructor(
        private httpClient: HttpClient) {
    }
    get(url, params): Promise<Object> {

        return this.sendRequest(this.baseUrl + url, 'get', null, params)
            .map((res) => {
                return res as Object
            })
            .toPromise();
    }
    post(url, body): Promise<Object> {
        return this.sendRequest(this.baseUrl + url, 'post', body)
            .map((res) => {
                return res as Object
            })
            .toPromise();
    }
    patch(url, body): Promise<Object> {
        return this.sendRequest(this.baseUrl + url, 'patch', body)
            .map((res) => {
                return res as Object
            })
            .toPromise();
    }
    sendRequest(url, type, body, params = null): Observable<any> {
        return this.httpClient[type](url, { params: params }, body)
    }
}

如果我收到HTTP错误(即404),我会得到一个令人讨厌的控制台消息: ERROR Error: Uncaught (in promise): [object Object] 来自 core.es5.js 如何在我的情况下处理它?

回答(9)

2 years ago

根据您的需要,您有一些选择 . 如果要基于每个请求处理错误,请在您的请求中添加 catch . 如果要添加全局解决方案,请使用 HttpInterceptor .

打开here the working demo plunker以获取以下解决方案 .

tl;博士

在最简单的情况下,您只需添加 .catch().subscribe() ,如:

import 'rxjs/add/operator/catch'; // don't forget this, or you'll get a runtime error
this.httpClient
      .get("data-url")
      .catch((err: HttpErrorResponse) => {
        // simple logging, but you can do a lot more, see below
        console.error('An error occurred:', err.error);
      });

// or
this.httpClient
      .get("data-url")
      .subscribe(
        data => console.log('success', data),
        error => console.log('oops', error)
      );

但是有更多细节,见下文 .

方法(本地)解决方案:记录错误并返回回退响应

如果只需要在一个地方处理错误,可以使用 catch 并返回默认值(或空响应),而不是完全失败 . 你也不需要 .map 只是为了施放,你可以使用通用函数 . 资料来源:Angular.io - Getting Error Details .

所以,一个通用的 .get() 方法,就像:

import { Injectable } from '@angular/core';
import { HttpClient, HttpErrorResponse } from "@angular/common/http";
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/of';
import 'rxjs/add/observable/empty';
import 'rxjs/add/operator/retry'; // don't forget the imports

@Injectable()
export class DataService {
    baseUrl = 'http://localhost';
    constructor(private httpClient: HttpClient) { }

    // notice the <T>, making the method generic
    get<T>(url, params): Observable<T> {
      return this.httpClient
          .get<T>(this.baseUrl + url, {params})
          .retry(3) // optionally add the retry
          .catch((err: HttpErrorResponse) => {

            if (err.error instanceof Error) {
              // A client-side or network error occurred. Handle it accordingly.
              console.error('An error occurred:', err.error.message);
            } else {
              // The backend returned an unsuccessful response code.
              // The response body may contain clues as to what went wrong,
              console.error(`Backend returned code ${err.status}, body was: ${err.error}`);
            }

            // ...optionally return a default fallback value so app can continue (pick one)
            // which could be a default value
            // return Observable.of<any>({my: "default value..."});
            // or simply an empty observable
            return Observable.empty<T>();
          });
     }
}

即使URL上的服务状况不佳,处理错误也会使应用程序继续运行 .

当您想要为每个方法返回特定的默认响应时,此每请求解决方案很有用 . 但是,如果您只关心错误显示(或具有全局默认响应),则更好的解决方案是使用拦截器,如下所述 .

运行working demo plunker here .

高级用法:拦截所有请求或响应

再次,Angular.io guide显示:

@ angular / common / http的一个主要特性是拦截,即声明位于应用程序和后端之间的拦截器的能力 . 当您的应用程序发出请求时,拦截器会在将其发送到服务器之前对其进行转换,拦截器可以在应用程序看到之前将响应转换回来 . 从身份验证到日志记录,这非常有用 .

当然,这可以用来以非常简单的方式处理错误(demo plunker here):

import { Injectable } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest, HttpResponse,
         HttpErrorResponse } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/of';
import 'rxjs/add/observable/empty';
import 'rxjs/add/operator/retry'; // don't forget the imports

@Injectable()
export class HttpErrorInterceptor implements HttpInterceptor {
  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(request)
      .catch((err: HttpErrorResponse) => {

        if (err.error instanceof Error) {
          // A client-side or network error occurred. Handle it accordingly.
          console.error('An error occurred:', err.error.message);
        } else {
          // The backend returned an unsuccessful response code.
          // The response body may contain clues as to what went wrong,
          console.error(`Backend returned code ${err.status}, body was: ${err.error}`);
        }

        // ...optionally return a default fallback value so app can continue (pick one)
        // which could be a default value (which has to be a HttpResponse here)
        // return Observable.of(new HttpResponse({body: [{name: "Default value..."}]}));
        // or simply an empty observable
        return Observable.empty<HttpEvent<any>>();
      });
  }
}

Providing your interceptor: 简单地声明上面的 HttpErrorInterceptor 并不会导致您的应用使用它 . 您需要将它作为拦截器提供wire it up in your app module,如下所示:

import { NgModule } from '@angular/core';
import { HTTP_INTERCEPTORS } from '@angular/common/http';
import { HttpErrorInterceptor } from './path/http-error.interceptor';

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

Note: 如果同时存在错误拦截器和一些本地错误处理,则很可能不会触发本地错误处理,因为拦截器在到达本地错误处理之前始终会处理错误 .

运行working demo plunker here .

2 years ago

随着 HTTPClient API的到来,不仅更换了 Http API,而且添加了一个新的 HttpInterceptor API .

AFAIK的目标之一是为所有HTTP传出请求和传入响应添加默认行为 .

因此,假设您要添加 default error handling behavior ,将 .catch() 添加到所有可能的http.get / post / etc方法中是非常难以维护的 .

这可以通过以下方式完成,例如使用 HttpInterceptor

import { Injectable } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest, HttpErrorResponse, HTTP_INTERCEPTORS } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import { _throw } from 'rxjs/observable/throw';
import 'rxjs/add/operator/catch';

/**
 * Intercepts the HTTP responses, and in case that an error/exception is thrown, handles it
 * and extract the relevant information of it.
 */
@Injectable()
export class ErrorInterceptor implements HttpInterceptor {
    /**
     * Intercepts an outgoing HTTP request, executes it and handles any error that could be triggered in execution.
     * @see HttpInterceptor
     * @param req the outgoing HTTP request
     * @param next a HTTP request handler
     */
    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        return next.handle(req)
            .catch(errorResponse => {
                let errMsg: string;
                if (errorResponse instanceof HttpErrorResponse) {
                    const err = errorResponse.message || JSON.stringify(errorResponse.error);
                    errMsg = `${errorResponse.status} - ${errorResponse.statusText || ''} Details: ${err}`;
                } else {
                    errMsg = errorResponse.message ? errorResponse.message : errorResponse.toString();
                }
                return _throw(errMsg);
            });
    }
}

/**
 * Provider POJO for the interceptor
 */
export const ErrorInterceptorProvider = {
    provide: HTTP_INTERCEPTORS,
    useClass: ErrorInterceptor,
    multi: true,
};

// app.module.ts

import { ErrorInterceptorProvider } from 'somewhere/in/your/src/folder';

@NgModule({
   ...
   providers: [
    ...
    ErrorInterceptorProvider,
    ....
   ],
   ...
})
export class AppModule {}

OP的一些额外信息:在没有强类型的情况下调用http.get / post / etc不是API的最佳用途 . 您的服务应如下所示:

// These interfaces could be somewhere else in your src folder, not necessarily in your service file
export interface FooPost {
 // Define the form of the object in JSON format that your 
 // expect from the backend on post
}

export interface FooPatch {
 // Define the form of the object in JSON format that your 
 // expect from the backend on patch
}

export interface FooGet {
 // Define the form of the object in JSON format that your 
 // expect from the backend on get
}

@Injectable()
export class DataService {
    baseUrl = 'http://localhost'
    constructor(
        private http: HttpClient) {
    }

    get(url, params): Observable<FooGet> {

        return this.http.get<FooGet>(this.baseUrl + url, params);
    }

    post(url, body): Observable<FooPost> {
        return this.http.post<FooPost>(this.baseUrl + url, body);
    }

    patch(url, body): Observable<FooPatch> {
        return this.http.patch<FooPatch>(this.baseUrl + url, body);
    }
}

从您的服务方法而不是 Observables 返回 Promises 是另一个错误的决定 .

还有一条建议:如果您使用的是 TYPE 脚本,那么请开始使用它的类型部分 . 您将失去该语言的最大优势之一:了解您正在处理的值的类型 .

如果您想要一个角度服务的好例子,请看一下at the following gist .

2 years ago

让我更新acdcjunior关于使用HttpInterceptor和最新RxJs功能(v.6)的答案 .

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

import { Observable, EMPTY, throwError, of } from 'rxjs';
import { catchError } from 'rxjs/operators';

@Injectable()
export class HttpErrorInterceptor implements HttpInterceptor {
  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

    return next.handle(request).pipe(
      catchError((error: HttpErrorResponse) => {
        if (error.error instanceof Error) {
          // A client-side or network error occurred. Handle it accordingly.
          console.error('An error occurred:', error.error.message);
        } else {
          // The backend returned an unsuccessful response code.
          // The response body may contain clues as to what went wrong,
          console.error(`Backend returned code ${error.status}, body was: ${error.error}`);
        }

        // If you want to return a new response:
        //return of(new HttpResponse({body: [{name: "Default value..."}]}));

        // If you want to return the error on the upper level:
        //return throwError(error);

        // or just return nothing:
        return EMPTY;
      })
    );
  }
}

2 years ago

你可能想要这样的东西:

this.sendRequest(...)
.map(...)
.catch((err) => {
//handle your error here
})

这在很大程度上取决于您如何使用您的服务,但这是基本情况 .

2 years ago

在@acdcjunior回答之后,这就是我实现它的方式

服务:

get(url, params): Promise<Object> {

            return this.sendRequest(this.baseUrl + url, 'get', null, params)
                .map((res) => {
                    return res as Object
                }).catch((e) => {
                    return Observable.of(e);
                })
                .toPromise();
        }

呼叫者:

this.dataService.get(baseUrl, params)
            .then((object) => {
                if(object['name'] === 'HttpErrorResponse') {
                            this.error = true;
                           //or any handle
                } else {
                    this.myObj = object as MyClass 
                }
           });

2 years ago

相当简单(与之前的API相比) .

来自(复制并粘贴)Angular official guide的来源

http
  .get<ItemsResponse>('/api/items')
  .subscribe(
    // Successful responses call the first callback.
    data => {...},
    // Errors will call this callback instead:
    err => {
      console.log('Something went wrong!');
    }
  );

2 years ago

如果您发现自己无法捕获此处提供的任何解决方案的错误,则可能是服务器未处理CORS请求 .

在那种情况下,Javascript,更不用说Angular,可以访问错误信息 .

在控制台中查找包含 CORBCross-Origin Read Blocking 的警告 .

此外,语法已更改以处理错误(如每个其他答案中所述) . 你现在使用管道运营商,如下:

this.service.requestsMyInfo(payload).pipe(
    catcheError(err => {
        // handle the error here.
    })
);

2 years ago

import { Observable, throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';

const PASSENGER_API = 'api/passengers';

getPassengers(): Observable<Passenger[]> {
  return this.http
    .get<Passenger[]>(PASSENGER_API)
    .pipe(catchError((error: HttpErrorResponse) => throwError(error)));
}

2 years ago

通过使用Interceptor,您可以捕获错误 . 以下是代码:

@Injectable()
export class ResponseInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    //Get Auth Token from Service which we want to pass thr service call
    const authToken: any = `Bearer ${sessionStorage.getItem('jwtToken')}`
    // Clone the service request and alter original headers with auth token.
    const authReq = req.clone({
      headers: req.headers.set('Content-Type', 'application/json').set('Authorization', authToken)
    });

    const authReq = req.clone({ setHeaders: { 'Authorization': authToken, 'Content-Type': 'application/json'} });

    // Send cloned request with header to the next handler.
    return next.handle(authReq).do((event: HttpEvent<any>) => {
      if (event instanceof HttpResponse) {
        console.log("Service Response thr Interceptor");
      }
    }, (err: any) => {
      if (err instanceof HttpErrorResponse) {
        console.log("err.status", err);
        if (err.status === 401 || err.status === 403) {
          location.href = '/login';
          console.log("Unauthorized Request - In case of Auth Token Expired");
        }
      }
    });
  }
}

你可以更喜欢this blog ..给它一个简单的例子 .