Can I deploy a war file with the mixture of JSP and servlet?

Question

I have a project, which the JSP has been created for view page, and the servlet was created to retrieve the database, but we have trouble to pass the session variable from servlet back to JSP, it is NULL, with different session ID.
Now, I try to add the servlet into the same JSP project, and deploy them as one war file, so, it will be called under the same subdirectory (Tomcat).
It failed to call the servlet, with the error message
Servlet FirstServlet is not available
I wonder whether this is valid, if it is, what I may lost, if it is not, how to pass the session variable between them.
Thanks.

Answer 1

I double checked the web.xml file, the FirstServlet was defined as servlet class, and the FirstServlet class was found under WEB-INF/classes/FirstServletPackage directory.
Here it is the web.xml file
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
<servlet-name>FirstServlet</servlet-name>
<servlet-class>FirstServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FirstServlet</servlet-name>
<url-pattern>/FirstServlet</url-pattern>
</servlet-mapping>
<session-config>
<session-timeout>
30
</session-timeout>
</session-config>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
and here it is the message from Tomcat log
May 28, 2009 5:09:43 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Allocate exception for servlet FirstServlet
java.lang.ClassNotFoundException: FirstServlet
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1094)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:808)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:129)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:595)
I will try to rename it, then test it again.