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Asked: 2026-06-07T15:39:41+00:00

what was i doing wrong ?? I am running Apache tomcat 7 as a

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what was i doing wrong ??

I am running Apache tomcat 7 as a service in win 7

my jsp code […\webapps\test\index.jsp ]

<jsp:useBean id="Counter" scope="session" class="aaa.Counter" />
<html>
<title>sfcsv</title>

<%
    try{
        int x = Counter.read_count(),z = Counter.get_id();
        if(x%2==0)
            out.println(x + " = even");
        else
            out.println(x + " = odd");

        out.println(z);
    }catch(Exception e){
    out.println(e);
    }
%>


</html>

the java code [..\webapps\test\WEB-INF\classes\aaa\Counter.java ]

package aaa;

public class Counter {

    private int count;
    private static int instance_counter;
    private final int id;

    public Counter(){
        instance_counter ++;
        id = instance_counter;
        count = 0;
    }

    public int read_count(){
        return count++;
    }

    public int get_id(){
        return id;
    }

}

expected output :

24 = even    1

output that I was getting :

24 = even

or

HTTP Status 500 - Unable to compile class for JSP: An error occurred at line: 8 in the jsp file: /index.jsp The method     get_id() is undefined for the type Counter 5: 6: <% 7: try{ 8: int x = Counter.read_count(),z = Counter.get_id(); 9:     if(x%2==0) 10: out.println(x + " = even"); 11: else Stacktrace:

type Exception report

message Unable to compile class for JSP: An error occurred at line: 8 in the jsp file: /index.jsp The method get_id()     is undefined for the type Counter 5: 6: <% 7: try{ 8: int x = Counter.read_count(),z = Counter.get_id(); 9: if(x%2==0)     10: out.println(x + " = even"); 11: else Stacktrace:

description The server encountered an internal error (Unable to compile class for JSP: An error occurred at line: 8 in     the jsp file: /index.jsp The method get_id() is undefined for the type Counter 5: 6: <% 7: try{ 8: int x =     Counter.read_count(),z = Counter.get_id(); 9: if(x%2==0) 10: out.println(x + " = even"); 11: else Stacktrace:) that     prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: Unable to compile class for JSP: 

An error occurred at line: 8 in the jsp file: /index.jsp
The method get_id() is undefined for the type Counter
5: 
6: <%
7:  try{
8:      int x = Counter.read_count(),z = Counter.get_id();
9:      if(x%2==0)
10:             out.println(x + " = even");
11:         else


Stacktrace:
    org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:102)
    org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:331)
    org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:469)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:378)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:353)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:340)
    org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:646)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:357)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.29 logs.

Apache Tomcat/7.0.29

EDIT: On restarting the computer the problem vanished

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1 Answer

  1. Editorial Team

    You already solved your problem but here are the appropriate options to get all your classes and JSP files to be reloaded or recompiled which might help in understanding what was going on in your case:

    Refreshing Java classes – Be sure to recompile your classes after applying changes to them. Also see the reloadable option for you web application context (default is false).

    Set to true if you want Catalina to monitor classes in /WEB-INF/classes/ and /WEB-INF/lib for changes, and automatically reload the web application if a change is detected.

    Refreshing JSP files – Please see the Tomcat Jasper docs for details on the development variable (defaults to true so I guess this is its value in your case) and the modificationTestInterval variable (defaults to 4 seconds) with which you may set the interval in which JSP files are checked for changes and compiled if necessary. Both are usually set in $CATALINA_BASE/conf/web.xml.

    Is Jasper used in development mode? If true, the frequency at which JSPs are checked for modification may be specified via the modificationTestInterval parameter.true or false, default true.

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