The solution was to enable file serving in ibm-web-ext.xml.
- Double-click on web.xml to open up the Web Application Deployment Description Editor.
- Select the "Open WebSphere Extensions Descriptor" link.
- Select the "Enable File Serving" checkbox and save your changes.
This adds the following line to ibm-web-ext.xml:
<enable-file-serving value="true"/>
Acknowledgement to CodeRanch for the solution.