[tomcat] How to config Tomcat to serve images from an external folder outside webapps?

You could have a redirect servlet. In you web.xml you'd have:

<servlet>
    <servlet-name>images</servlet-name>
    <servlet-class>com.example.images.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>images</servlet-name>
    <url-pattern>/images/*</url-pattern>
</servlet-mapping>

All your images would be in "/images", which would be intercepted by the servlet. It would then read in the relevant file in whatever folder and serve it right back out. For example, say you have a gif in your images folder, c:\Server_Images\smilie.gif. In the web page would be <img src="http:/example.com/app/images/smilie.gif".... In the servlet, HttpServletRequest.getPathInfo() would yield "/smilie.gif". Which the servlet would find in the folder.