AttachmentDownloader

Background and Use Cases

FineReport involves extensive file upload and download operations. The AttachmentDownloader interface allows developers to customize the download logic for attachments.

Interface Definition

package com.fr.stable.fun;

import com.fr.stable.fun.mark.Selectable;

public interface AttachmentDownloader extends Selectable {
    String XML_TAG = "AttachmentDownloader";
    int CURRENT_LEVEL = 1;

    void download(HttpServletRequest req, HttpServletResponse res,
                  String id, String[] idArr) throws Exception;

    String createDownloadScript(String downloadURL);
}

The Selectable parent interface requires implementing:

Selector selector();

Supported Versions

Plugin Registration

Add the following node in plugin.xml:

<extra-core>
    <AttachmentDownloader class="your class name"/>
</extra-core>

How It Works

The system retrieves all registered implementations via ExtraClassManager.getInstance().getArray(AttachmentDownloader.XML_TAG). When processing a request, the selector (Selector) evaluates each implementation in order; the first matching implementation takes effect. If no match is found, the default handler is used.

Notes

• The request parameter id is used to pass the attachment identifier
• Multiple implementations can be registered, but only one implementation takes effect per download request (determined by the selector)
• The createDownloadScript() method only applies to attachments computed by cell formulas (not files that have been uploaded), and only DefaultAttachmentDownloader should be used within this method to avoid conflicts

Useful Links

• Demo: demo-attachment-downloader