AJAX实现文件上传功能报错Current request is not a multipart request详解

When using AJAX to upload files, you may encounter the error "Current request is not a multipart request". This error occurs because the request is not formatted correctly to handle file uploads. File uploads require a specific content type, multipart/form-data, which indicates that the request contains both text data and binary data (the file).

To resolve this error, you need to ensure that the AJAX request is configured with the correct content type. Here's how to do it:

1. Set the Content Type Header:

Before sending the AJAX request, set the Content-Type header to multipart/form-data. This can be done using the setRequestHeader() method of the XMLHttpRequest object:

xhr.setRequestHeader('Content-Type', 'multipart/form-data');

2. Use FormData Object:

Instead of directly sending the file data as a string, use the FormData object to construct the request payload. The FormData object allows you to add key-value pairs for both text data and file data.

const formData = new FormData();
formData.append('file', fileInput.files[0]);
formData.append('otherData', 'someValue');

xhr.send(formData);

3. Check for Browser Compatibility:

Ensure that the browser you're using supports the FormData object and the multipart/form-data content type. Older browsers may require additional polyfills or workarounds.

4. Server-Side Configuration:

On the server-side, make sure your code is configured to handle multipart form data requests. This may involve using specific libraries or frameworks that support file uploads.

5. Verify File Selection:

Check if the file input element has a selected file before attempting to upload it. An empty file selection could also lead to this error.

6. Use Libraries or Plugins:

Consider using dedicated JavaScript libraries or plugins for file uploads, such as jQuery File Upload or Dropzone. These libraries simplify the process and handle common file upload scenarios.

By following these steps, you should be able to successfully upload files using AJAX and avoid the "Current request is not a multipart request" error. Remember to check for browser compatibility and server-side configuration if the issue persists.