Content Disposition Header
The BinariesServlet can add the Content-Disposition header field to force downloaded files to be treated as an attachment with a valid file name by the browser. For example, if properly set, the header can be like this example:
Content-Disposition: attachment; filename=genome.jpeg
For the details of "Content-Disposition" header, you can refer to http://en.wikipedia.org/wiki/MIME#Content-Disposition.
MIME type configuration for BinariesServlet in web.xml
To configure which MIME types to enable content disposition headers, set the contentDispositionContentTypes init param in the web.xml in which this servlet is defined. When the BinariesServlet tries to serve a jcr data, it reads jcr:mimeType property. So, if the mimeType property value is found in the contentDispositionContentTypes configuration, then the data will be written with Content-Disposition header. For example:
<init-param> <param-name> contentDispositionContentTypes </param-name> <param-value> application/pdf, application/rtf, application/excel </param-value> </init-param>
In the above init param configuration, you can also set glob style configurations such as */* or application/* like the following example:
<init-param> <param-name> contentDispositionContentTypes </param-name> <param-value> application/* </param-value> </init-param>
By default, the BinariesServlet uses the handle name of the image, asset, or document the resource is embedded in. It is also possible to configure a JCR property to get the file name from, for example:
<init-param> <param-name> contentDispositionFilenameProperty </param-name> <param-value> demosite:filename demosite:attachmentname </param-value> </init-param>
If multiple property names are configured, then the first available JCR property will be chosen. If none of the properties are available for the resource, or if no properties are configured, the handle name is used.
Appendix: File name encoding issue
The file name value in Content-Disposition header is automatically encoded for each browser. For normal standard browsers, the file name is encoded by the standard MIME encoding mechanism. (e.g. "=?iso-8859-1?Q?=A1Hola,_se=F1or!?=") However, for Microsoft Internet Explorer or Opera browser, the file name is URL-encoded for proper display.