How to save api json response as file in angular


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You can now export your bookmarks and snippets from Bookmarks.dev for backup or other purposes. You can do that by going to your dashboard and click Export my bookmarks button. A dialog will pop up to ask whether you want to see your bookmarks or snippets in the browser(this opens a new window) or save them as a json file:

Export my snippets

How it is implemented behind the scenes?

I will show you the implementation for snippets export case. For bookmarks is basically the same.

When you click the Export my snippets button:

  <button type="button" class="btn btn-outline-primary" title="Export all my snippets"
          (click)="exportMySnippets()">
    Export my snippets
  </button>

the exportMySnippts() function is called which calls the backend REST API, where we wait for the response to then invoke the downloadFile with it:

  exportMySnippets() {
    this.personalSnippetsService.getAllMySnippets(this.userId).subscribe(data =>
      this.downloadFile(data)
    );
  }

In the downloadFile function we create a blob1 from the data, get the blob’s url via window.URL.createObjectURL(blob) and pass it to the dialog presented to the user:

  private downloadFile(data: Snippet[]) {
    const blob = new Blob([JSON.stringify(data, null, 2)], {type: 'application/json'});
    const dialogConfig = new MatDialogConfig();

    dialogConfig.autoFocus = true;
    dialogConfig.data = {
      blobUrl: window.URL.createObjectURL(blob),
      backupType: 'snippets'
    };

    this.backupBookmarksDialog.open(BackupBookmarksDialogComponent, dialogConfig);
  }

Angular dialog

In the dialog we have the two buttons:

  • one to download the file (“save as” functionality) which is triggered by providing input to the href and download attributes of the a anchor element
  • the View in browser functionality which opens a new window with the blob’s url we created earlier - window.open(this.blobUrl);
<h2 mat-dialog-title>Download personal </h2>

<hr>

<mat-dialog-actions class="app-dialog-actions">
  <a [href]="sanitizedBlobUrl" [download]="filename" type="button" class="btn btn-primary btn-sm mr-2" (click)="download()"><i class="fas fa-download"></i> Download
  </a>
  <button type="button" class="btn btn-primary btn-sm mr-2" (click)="viewInBrowser()"><i class="fas fa-eye"></i> View in browser
  </button>
  <button type="button" class="btn btn-secondary btn-sm" (click)="close()">Close <i class="fas fa-window-close"></i></button>
</mat-dialog-actions>

I had to sanitize the url passed to the href attribute of the a anchor element in angular, via the DomSanitizer and its method bypassSecurityTrustUrl:

export class BackupBookmarksDialogComponent implements OnInit {

  backupType: string; // 'bookmarks' | 'snippets';
  blobUrl: any;
  sanitizedBlobUrl: any;
  filename: string;

  constructor(
    private dialogRef: MatDialogRef<BackupBookmarksDialogComponent>,
    private router: Router,
    @Inject(MAT_DIALOG_DATA) data,
    private sanitizer: DomSanitizer
  ) {
    this.sanitizedBlobUrl = this.sanitizer.bypassSecurityTrustUrl(data.blobUrl);
    this.blobUrl = data.blobUrl;
    this.backupType = data.backupType;
    const currentDate = new Date();
    this.filename = `${this.backupType}_${currentDate.toISOString()}.json`;
  }

  ngOnInit() {
  }

  close() {
    this.dialogRef.close();
  }

  download() {
  }

  viewInBrowser() {
    window.open(this.blobUrl);
  }
}

Bypassing built-in security has to be well thought. See Angular’s security guide for more information.

As an alternative you could also use FileSave.js, which ads an HTML5 saveAs() FileSave implementation, but I wanted to avoid adding another library to the project

References

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Adrian Matei

Adrian Matei
Life force expressing itself as a coding capable human being

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