How Can Ajax Asynchronously Trigger File Save Dialogs for Enhanced User Experience?

Asynchronous File Downloads with Ajax: Unlocking the File Save Dialog

In this digital age, file downloads are ubiquitous. With Ajax's capabilities, we can enhance the user experience by allowing file downloads asynchronously without interrupting webpage interactions.

The Problem

When using a Struts2 action for server-side file downloading, invoking the action via jQuery retrieves the data in a binary stream. However, the desired outcome is to trigger a file save dialog that allows users to save the file locally.

Modern Browser Solution

For modern browsers, the following approach is recommended:

<br>fetch('your-download-endpoint').then(resp => resp.blob()).then(blob => {<br>  const url = window.URL.createObjectURL(blob);<br>  const a = document.createElement('a');<br>  a.style.display = 'none';<br>  a.href = url;<br>  a.download = 'your-file-name'; // Specify the desired filename<br>  document.body.appendChild(a);<br>  a.click();<br>  window.URL.revokeObjectURL(url);<br>});<br>

This code creates a temporary URL for the blob data, which is then attached to an anchor element that is appended to the document body. Clicking on this hidden anchor element triggers the file save dialog, and once the download is complete, the temporary URL is revoked.

Considerations

While this approach works well for small to medium-sized files, it is important to consider memory consumption for very large downloads. If you anticipate large files, alternative techniques such as using an iframe and a cookie may be more suitable.

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