"jsp:useBean" Requires Fully Qualified Class Name

JSP Tutorials - Herong's Tutorial Examples

∟JavaBean Objects and "useBean" Action Elements

∟"jsp:useBean" Requires Fully Qualified Class Name

This section provides a tutorial example showing the JSP error, if the short class name instead of the fully qualified class name is used in the 'jsp:useBean' action element.

While testing JavaBeen, I noticed an error with Tomcat 9. It relates to the "class" attribute in the "useBean" JSP element.

Here is an example JSP page that uses the class name, not the fully qualified class name, in the "useBean" JSP element:

<?xml version="1.0"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.1">
<!-- UseBeanClassError.jsp
 - Copyright (c) 2006 HerongYang.com. All Rights Reserved.
-->
<jsp:directive.page contentType="text/html"/>
<html><body>
<jsp:directive.page import="herong.CacheBean"/>
<jsp:useBean id="b" class="CacheBean"/>
<jsp:setProperty name="b" property="text" value="Hello world!"/>
Property from my JavaBean:
<jsp:getProperty name="b" property="text"/>
<br/>
Info from my JavaBean:
<jsp:expression>b.getInfo()</jsp:expression>
</body></html>
</jsp:root>

Deploy this JSP page to the Tomcat 9 server and view it in a Web browser. You will get this error:

HTTP Status 500 – Internal Server Error
Type Exception Report

Message /UseBeanClassError.jspx (line: [9], column: [40]) The value for
 the useBean class attribute [CacheBean] is invalid.

Description The server encountered an unexpected condition that prevented
 it from fulfilling the request.

Exception
org.apache.jasper.JasperException: /UseBeanClassError.jspx
 (line: [9], column: [40]) The value for the useBean class attribute
 [CacheBean] is invalid.
 org.apache.jasper.compiler.DefaultErrorHandler.jspError(...)
 org.apache.jasper.compiler.ErrorDispatcher.dispatch(...)
 ...
 org.apache.jasper.compiler.Generator.generate(Generator.java:3667)
 org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:257)
 org.apache.jasper.compiler.Compiler.compile(Compiler.java:385)
 org.apache.jasper.compiler.Compiler.compile(Compiler.java:362)
 org.apache.jasper.compiler.Compiler.compile(Compiler.java:346)
 org.apache.jasper.JspCompilationContext.compile(...)
 org.apache.jasper.servlet.JspServletWrapper.service(...)
 org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386)
 org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
 org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

Apache Tomcat/9.0.12

The error message is not that clear. But I know the issue is caused by the "class" attribute in the "useBean" element. You must provide the fully qualified class name like herong.CacheBean, not the short class name.