"NoClassDefFoundError" Exception

JSP Tutorials - Herong's Tutorial Examples

∟JavaBean Objects and "useBean" Action Elements

∟"NoClassDefFoundError" Exception

This section describes the compilation error on a JSP page that tries to use a JavaBean class, but the class bytecode is not accessible. You will get a NoClassDefFoundError Java exception or a JSP to Servlet class conversion error.

One common issue involved in the use JavaBean classes in JSP pages is the JavaBean class bytecode files () are not accessible by the Tomcat server. You can follow these steps to experience this issue:

1. Shut down the Tomcat server and remove TempratureConvertorBean.class file from the Tomcat server:

herong> \local\tomcat\bin\shutdown.bat

herong> del \local\tomcat\webapps\ROOT\WEB-INF\classes \
   \herong\TempratureConvertorBean.class

2. Start the Tomcat server and view the JSP page:

herong> \local\tomcat\bin\startup.bat

herong> type \local\tomcat\webapps\ROOT\TempratureConvertor.jspx

<?xml version="1.0"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.3">
<!-- TempratureConvertor.jspx
 - Copyright (c) 2006 HerongYang.com. All Rights Reserved.
-->
<jsp:directive.page contentType="text/html"/>
<html><body>
<jsp:useBean id="b" class="herong.TempratureConvertorBean"/>
<jsp:expression>b.getInfo()</jsp:expression><br/>
Setting property "fahrenheit" to 70.0.<br/>
<jsp:setProperty name="b" property="fahrenheit" value="70.0"/>
Getting property "celsius" back:
<jsp:getProperty name="b" property="celsius"/>
<br/>
</body></html>
</jsp:root>

3. Visit http://localhost:8080/TempratureConvertor.jspx with a browser. The "NoClassDefFoundError" Tomcat error will show up:

HTTP Status 500 - javax.servlet.ServletException:
java.lang.NoClassDefFoundError: herong/TempratureConvertorBean

type Exception report

message javax.servlet.ServletException:
   java.lang.NoClassDefFoundError: herong/TempratureConvertorBean

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

exception
org.apache.jasper.JasperException: javax.servlet.ServletException:
   java.lang.NoClassDefFoundError: herong/TempratureConvertorBean
   org.apache.jasper.servlet.JspServletWrapper.handleJspException()
   org.apache.jasper.servlet.JspServletWrapper.service()
   org.apache.jasper.servlet.JspServlet.serviceJspFile()
   org.apache.jasper.servlet.JspServlet.service()
   javax.servlet.http.HttpServlet.service()

root cause

javax.servlet.ServletException:
   java.lang.NoClassDefFoundError: herong/TempratureConvertorBean
   org.apache.jasper.runtime.PageContextImpl.doHandlePageException()
   org.apache.jasper.runtime.PageContextImpl.handlePageException()
   org.apache.jsp.TempratureConvertor_jspx._jspService()
   org.apache.jasper.runtime.HttpJspBase.service()
   javax.servlet.http.HttpServlet.service()
   org.apache.jasper.servlet.JspServletWrapper.service()
   org.apache.jasper.servlet.JspServlet.serviceJspFile()
   org.apache.jasper.servlet.JspServlet.service()
   javax.servlet.http.HttpServlet.service()

4. Do another test by adding the "page import" element in the JSP page:

herong> edit \local\tomcat\webapps\ROOT
   \TempratureConvertorModified.jspx

<?xml version="1.0"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.1">
<!-- TempratureConvertorModified.jspx
 - Copyright (c) 2006 HerongYang.com. All Rights Reserved.
-->
<jsp:directive.page contentType="text/html"/>
<jsp:directive.page import="herong.TempratureConvertorBean"/>
<html><body>
<jsp:useBean id="b" class="herong.TempratureConvertorBean"/>
<jsp:expression>b.getInfo()</jsp:expression><br/>
Setting property "fahrenheit" to 70.0.<br/>
<jsp:setProperty name="b" property="fahrenheit" value="70.0"/>
Getting property "celsius" back:
<jsp:getProperty name="b" property="celsius"/>
<br/>
</body></html>
</jsp:root>

5. Visit the modified JSP page. Interestingly, a new error will show up. This time is a JSP to Servlet class conversion error:

HTTP Status 500 - /TempratureConvertorModified.jspx
   () The value for the useBean class attribute
   herong.TempratureConvertorBean is invalid.

type Exception report

message /TempratureConvertorModified.jspx ()
The value for the useBean class attribute
herong.TempratureConvertorBean is invalid.

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

exception
org.apache.jasper.JasperException:
   /TempratureConvertorModified.jspx ()
   The value for the useBean class attribute
   herong.TempratureConvertorBean is invalid.
   org.apache.jasper.compiler.DefaultErrorHandler.jspError()
   org.apache.jasper.compiler.ErrorDispatcher.dispatch()
   org.apache.jasper.compiler.ErrorDispatcher.jspError()
   org.apache.jasper.compiler.Generator$GenerateVisitor.visit()
   org.apache.jasper.compiler.Node$UseBean.accept()
   org.apache.jasper.compiler.Node$Nodes.visit()
   org.apache.jasper.compiler.Node$Visitor.visitBody()
   org.apache.jasper.compiler.Generator$GenerateVisitor.visit()
   org.apache.jasper.compiler.Node$UninterpretedTag.accept()
   org.apache.jasper.compiler.Node$Nodes.visit()
   org.apache.jasper.compiler.Node$Visitor.visitBody()
   org.apache.jasper.compiler.Generator$GenerateVisitor.visit()
   org.apache.jasper.compiler.Node$UninterpretedTag.accept()
   org.apache.jasper.compiler.Node$Nodes.visit()
   org.apache.jasper.compiler.Node$Visitor.visitBody()
   org.apache.jasper.compiler.Node$Visitor.visit()
   org.apache.jasper.compiler.Node$JspRoot.accept()
   org.apache.jasper.compiler.Node$Nodes.visit()
   org.apache.jasper.compiler.Node$Visitor.visitBody()
   org.apache.jasper.compiler.Node$Visitor.visit()
   org.apache.jasper.compiler.Node$Root.accept()
   org.apache.jasper.compiler.Node$Nodes.visit()
   org.apache.jasper.compiler.Generator.generate()
   org.apache.jasper.compiler.Compiler.generateJava()
   org.apache.jasper.compiler.Compiler.compile()
   org.apache.jasper.compiler.Compiler.compile()
   org.apache.jasper.compiler.Compiler.compile()
   org.apache.jasper.JspCompilationContext.compile()
   org.apache.jasper.servlet.JspServletWrapper.service()
   org.apache.jasper.servlet.JspServlet.serviceJspFile()
   org.apache.jasper.servlet.JspServlet.service()
   javax.servlet.http.HttpServlet.service()