How can I fix this issue?

I have attached the java class.
Category.java

My guess is there is more going on farther up in the stack trace.  If you look in the allCategories method you will see the following lines:

                catch (SQLException sqlException)
		{
			sqlException.printStackTrace();
			return null;
		}

		catch (ClassNotFoundException classNotFound)
		{
			classNotFound.printStackTrace();
			return null;
		}

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I am guessing that one of those two exceptions are being thrown.  Can you look farther up in your logs and see if there is another stacktrace being printed out before the null pointer.  That will probably tell you which is happening.

This is what I get...

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /category.jsp at line 54

51: Category dbcategory=new Category();
52: ArrayList<Category> T=new ArrayList<Category>();
53: T= dbcategory.allCategories();
54: Iterator<Category> itr = T.iterator();
55: while(itr.hasNext())
56: {
57:     dbcategory=itr.next();


Stacktrace:
      org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
      org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
      org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
      org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
      org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

root cause

java.lang.NullPointerException
      org.apache.jsp.category_jsp._jspService(category_jsp.java:116)
      org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
      org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
      org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
      org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
      org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

note The full stack trace of the root cause is available in the Apache Tomcat/6.0.26 logs.

sorry this one...

Apr 8, 2011 10:45:06 PM org.apache.catalina.startup.HostConfig deployDescriptor
INFO: Deploying configuration descriptor HoltDistributors.xml
java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1073)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3603)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3535)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:934)
        at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:4104)
        at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1299)
        at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2338)
        at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2371)
        at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2163)
        at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:794)
        at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:407)
        at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:378)
        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
        at java.sql.DriverManager.getConnection(DriverManager.java:582)
        at java.sql.DriverManager.getConnection(DriverManager.java:185)
        at inventory.Category.allCategories(Category.java:246)
        at org.apache.jsp.category_jsp._jspService(category_jsp.java:115)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        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:298)
        at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859)
        at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)
        at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1555)
        at java.lang.Thread.run(Thread.java:662)
java.lang.NullPointerException
        at inventory.Category.allCategories(Category.java:279)
        at org.apache.jsp.category_jsp._jspService(category_jsp.java:115)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        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:298)
        at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859)
        at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)
        at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1555)
        at java.lang.Thread.run(Thread.java:662)

So looking at that it definitly looks like you are having some database connection issues.  Access denied for user 'root'@'localhost' (using password: YES).  Is that the right password for your database.  I would start looking at that.  There are many passwords in that code you sent, I would guess that the password is not right or something on those lines.

My password is right. Is there anything i need to put in the CLASSPATH?

It really just seems like you can't connect to your database from webserver.  There could be several possibilities.  Take a look at this article. I think it could help you .

http://dev.mysql.com/doc/refman/5.1/en/access-denied.html