Jakarta Struts Cookbook

11.12. Limiting the Size of Uploaded Files

Problem

You want to limit the size of a file to be uploaded to your application.

Solution

In the struts-config.xml file, set the maxFileSize attribute on the controller element to the maximum accepted size (in bytes) for an uploaded file. In this example, a single uploaded file must be smaller than 700 KB:

<controller maxFileSize="700K"/>

Discussion

Whether intended or not, users may attempt to upload excessively large files to your web application. In most cases, the user accidentally picked the wrong file; however, a malicious user could be attempting to bring down your application. You can restrict uploads to a maximum file size using the maxFileSize attribute on the controller element in your struts-config.xml file. The value for this attribute is expressed as an integer value optionally followed by a "K," "M," or "G," interpreted as kilobytes, megabytes or gigabytes, respectively. If you specify the integer valuewith no units indicated, the value will be interpreted as bytes.

If you attempt to upload a file larger than the acceptable maximum, the FormFile property of the ActionForm will be null. You can handle this condition in your Action that processes the upload, as shown in Example 11-25.

Example 11-25. Handling null FormFile property (partial)

public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception { // Get the form file property from the form UploadForm ...