Project compiles fine in Eclipse but not with ant file

I am making a simple java-based web application using Eclipse and Tomcat.  The Eclipse project compiles without any problem in Eclipse, using the compilation capability provided within Eclipse.  But, when I try to compile use an Ant build file (build.xml) within the Eclipse project, it tells me that it cannot find the servlet package when Eclipse was able to.  This package is definitely recognised by Eclipse because when I remove the jar file from Eclipse, the Eclipse compiler complains.  I am very stuck on this, help would be much appreciated.  Here is the compile error from the Ant build:


Buildfile: C:\TenantLife\workspace\RABProj\build.xml
init:
compile:
    [javac] Compiling 8 source files to C:\apache-tomcat-5.5.16\webapps\bikestore\war\WEB-INF\classes
    [javac] C:\apache-tomcat-5.5.16\webapps\bikestore\src\com\springbook\BikesController.java:6: package javax.servlet.http does not exist
    [javac] import javax.servlet.http.HttpServletResponse;
    [javac] ^
    [javac] C:\apache-tomcat-5.5.16\webapps\bikestore\src\com\springbook\BikesController.java:7: package javax.servlet.http does not exist
    [javac] import javax.servlet.http.HttpServletRequest;
    [javac] ^
    [javac] C:\apache-tomcat-5.5.16\webapps\bikestore\src\com\springbook\BikesController.java:21: cannot resolve symbol
    [javac] symbol  : class HttpServletRequest
    [javac] location: class com.springbook.BikesController
    [javac] public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
    [javac] ^
    [javac] C:\apache-tomcat-5.5.16\webapps\bikestore\src\com\springbook\BikesController.java:21: cannot resolve symbol
    [javac] symbol  : class HttpServletResponse
    [javac] location: class com.springbook.BikesController
    [javac] public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
    [javac] ^
    [javac] C:\apache-tomcat-5.5.16\webapps\bikestore\src\com\springbook\EditBikeController.java:20: cannot resolve symbol
    [javac] symbol  : class HttpServletRequest
    [javac] location: class com.springbook.EditBikeController
    [javac] public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
    [javac] ^
    [javac] C:\apache-tomcat-5.5.16\webapps\bikestore\src\com\springbook\EditBikeController.java:20: cannot resolve symbol
    [javac] symbol  : class HttpServletResponse
    [javac] location: class com.springbook.EditBikeController
    [javac] public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
    [javac] ^
    [javac] C:\apache-tomcat-5.5.16\webapps\bikestore\src\com\springbook\SubmitBikeController.java:21: cannot resolve symbol
    [javac] symbol  : class HttpServletRequest
    [javac] location: class com.springbook.SubmitBikeController
    [javac] public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response)
    [javac] ^
    [javac] C:\apache-tomcat-5.5.16\webapps\bikestore\src\com\springbook\SubmitBikeController.java:21: cannot resolve symbol
    [javac] symbol  : class HttpServletResponse
    [javac] location: class com.springbook.SubmitBikeController
    [javac] public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response)
    [javac] ^
    [javac] 8 errors

BUILD FAILED
C:\TenantLife\workspace\RABProj\build.xml:41: Compile failed; see the compiler error output for details.

Total time: 2 seconds