I do not have much experience with Java on Linux. On a Windows platform I would make sure that the CLASSPATH includes the necessary classes (in you case the javax.servlet.* classes).
Using, for instance, TOMCAT these would probably be packaged in jar files in the %TOMCAT_HOME%\server\lib directory or some such place. Try doing a simple search in the filesystem starting with the root directory of your JSP server searching all "jar" (and perhaps zip or tar or whatever packaged files are called on Linux) for occurences of "javax.servlet". You most likely just need to add any jars found by such a procedure to the CLASSPATH environment variable.
If the search doesn't turn up anything try downloading what you need from SUN. You could try:
http://java.sun.com/products/servlet/
Again:
I do not have much experience with Java on Linux so my advice may be of no value.