mirror of https://github.com/abpframework/abp.git
Sinan Öztürk
3 years ago
6 changed files with 132 additions and 146 deletions
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# HTTP Error Handling |
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When the `RestService` is used, all HTTP errors are reported to the [`HttpErrorReporterService`](./HTTP-Error-Reporter-Service), and then `ErrorHandler`, a service exposed by the `@abp/ng.theme.shared` package automatically handles the errors. |
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## Custom HTTP Error Handler |
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A custom HTTP error handler service can be registered to an injection token named **`CUSTOM_ERROR_HANDLERS`**. ABP has some default error handlers, you can see them [here](https://github.com/abpframework/abp/blob/dev/npm/ng-packs/packages/theme-shared/src/lib/providers/error-handlers.provider.ts). |
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### How ABP handles errors and How to add new one? |
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- First of all it will be better to understand how ABP handles errors. |
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- ABP error handler services are implements the interface of **CustomHttpErrorHandlerService**. |
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**Interface of `CUSTOM_ERROR_HANDLERS`** |
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```ts |
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interface CustomHttpErrorHandlerService { |
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readonly priority: number; |
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canHandle(error: unknown): boolean; |
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execute(): void; |
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} |
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``` |
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- **`priority`** ABP sorts the services according to the number of the priority variable. Higher priority will be checked first. You can think this as a z-index property in CSS. |
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- **`canHandle(error: unknown): boolean :`** Check if the service can handle the error. Returns boolean. |
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- **`execute(): void :`** If the service can handle the error, then run the execute method. |
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**In Summarry** |
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- Services are sorted by their priority number. |
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- Start from highest priority service and run canHandle() method. Pick the service if can handle the error, if not check next service. |
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- If the service found, run the execute method of a service. Done. |
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See an example: |
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```ts |
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// custom-error-handler.service.ts |
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import { inject, Injectable } from "@angular/core"; |
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import { HttpErrorResponse } from "@angular/common/http"; |
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import { CustomHttpErrorHandlerService } from "@abp/ng.theme.shared"; |
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import { CUSTOM_HTTP_ERROR_HANDLER_PRIORITY } from "@abp/ng.theme.shared"; |
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import { ToasterService } from "@abp/ng.theme.shared"; |
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@Injectable({ providedIn: "root" }) |
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export class MyCustomErrorHandlerService |
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implements CustomHttpErrorHandlerService |
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{ |
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// You can write any number here, ex: 9999 |
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readonly priority = CUSTOM_HTTP_ERROR_HANDLER_PRIORITY.veryHigh; |
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private toaster = inject(ToasterService); |
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private error: HttpErrorResponse | undefined = undefined; |
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// What kind of error should be handled by this service? You can decide it in this method. If error is suitable to your case then return true; otherwise return false. |
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canHandle(error: unknown): boolean { |
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if (error instanceof HttpErrorResponse && error.status === 400) { |
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this.error = error; |
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return true; |
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} |
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return false; |
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} |
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// If this service is picked from ErrorHandler, this execute method will be called. |
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execute() { |
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this.toaster.error( |
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this.error.error?.error?.message || "Bad request!", |
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"400" |
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); |
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} |
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} |
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``` |
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```ts |
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// app.module.ts |
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import { CUSTOM_ERROR_HANDLERS, ... } from '@abp/ng.theme.shared'; |
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import { MyCustomErrorHandlerService } from './custom-error-handler.service'; |
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@NgModule({ |
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// ... |
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providers: [ |
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// ... |
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{ provide: CUSTOM_ERROR_HANDLERS, useExisting: MyCustomErrorHandlerService, multi: true } |
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] |
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}) |
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export class AppModule {} |
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``` |
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In the example above: |
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- Created a service named `MyCustomErrorHandlerService`, and provided via `useExisting` key because we dont want another instance of it. And set `multi` key to true because ABP default error handlers are also provided with **CUSTOM_ERROR_HANDLERS** injection token. |
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- 400 errors are handled from custom `MyCustomErrorHandlerService`. When a 400 error occurs, backend error message will be displayed as shown below: |
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**Note 1:** If your service cannot handle the error. Then ABP will check the next Error Service. |
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**Note 2:** If none of the service handle the error. Then basic confirmation message about the error will be shown to the user. |
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**Note 3:** You can provide more than one service, with CUSTOM_ERROR_HANDLER injection token. |
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**Note 4:** If you want your custom service to be evaluated (checked) earlier, set the priority variable high. |
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