请进来看看：一个关于包的问题！！！

我在下面的java程序中import javax.servlet.http.HttpSession接口，在编译的时候报错：package javax.servlet.http does not exist 这是怎么回事啊，哪位高手帮个忙！！！
环境变量：classpath已经设置为：.;D:\Program File\Apache Software Foundation\Tomcat 5.0\common\lib\servlet-api.jar;D:\Program Files\Apache Software Foundation\Tomcat 5.0\common\lib\jsp-api.jar;D:\j2sdk1.4.2_03\lib\tools.jar;D:\j2sdk1.4.2_03\lib\dt.jar;D:\j2sdk1.4.2_03\jre\lib\rt.jar

程序如下：
package com.wrox.errors;

import java.beans.*;
import javax.servlet.jsp.PageContext;
import javax.servlet.http.HttpSession;
import java.lang.Exception;

public class User extends Object implements java.io.Serializable {

public User() {}

private String username;
private String password;

public void setUsername(String name) {
username = name;
}

public String getUsername() {
return username;
}

public void setPassword(String pass) {
password = pass;
}

public void validateUser() throws Exception {
if (!(username.equals("Casey") && password.equals("Kochmer"))) {
Exception trouble = new Exception("Couldn't validate your password!");
throw trouble;
}
}
}