tomcat 7 shows compile error in a hello world jsp

Question

Please have a look at the info

• Objective: To run a JSP page which calls a java class, both residing on tomcat server

•Environment
Server environment: Linux
Server: Tomcat7.0.27
IDE: none

•JSP (all it does is display a string)

<%@page import="HelloWorld.HelloWorld" %>  
<HTML>  
<HEAD>  
<TITLE>Hello World/TITLE>  
</HEAD>  
<BODY>  
<H1>Hello World</H1>  
String is: <%= HelloWorld.HelloWorld.display() %>  
</BODY>  
</HTML>

•JSP location:TOMCAT/webapps/hello/hello.jsp

•Java class(all it does is return a string)
package HelloWorld;

public class HelloWorld {  
public static String display() {  
 return "Hello World!"; // Display the string.  
   }  
}

•Java class location: TOMCAT/webapps/hello/WEB-INF/classes/HelloWorld/HelloWorld.class •Java class compile action: javac -classpath TOMCAT/lib/servlet-api.jar:. -d /home/user/ HelloWorld.java

•WEB.XML

<?xml version="1.0" encoding="Cp1252"?>  
<!DOCTYPE web-app PUBLIC '-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN' 'http://java.sun.com/dtd/web-app_2_3.dtd'>  
<web-app>  
<display-name>hello</display-name>  
<description>no description</description>  
<servlet>  
<servlet-name>hello</servlet-name>  
<display-name>hello</display-name>  
<description>no description</description>  
<jsp-file>/hello.jsp</jsp-file>  
</servlet>  
<session-config>  
<session-timeout>30</session-timeout>  
</session-config>  
</web-app>

•Actions: o Copy java class to directory o Clean TOMCAT/work directory o Shutdown TOMCAT o Startup TOMCAT o Open server:8080/hello/hello.jsp

•Issue: HTTP Status 500 org.apache.jasper.JasperException: Unable to compile class for JSP: An error occurred at line: 14 in the generated java file The import HelloWorld cannot be resolved An error occurred at line: 8 in the jsp file: /hello.jsp HelloWorld cannot be resolved 5: </HEAD> 6: <BODY> 7: <H1>Hello World</H1> 8: String is : <%= HelloWorld.HelloWorld.display() %> 9: </BODY> 10: </HTML> Stacktrace:org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:102)

There is no syntax error in calling PackageName.ClassName.StringReturningMethod() in JSP The class is in package folder.

What is causing it?

Thanks,

Whoa, uppercased HTML, Scriptlets, CP1252 XML encoding and a Servlet 2.3 compatible web.xml. All signs from how JSP/HTML development is (badly) done more than a decade ago. Are you absolutely positive that you're reading the right and up to date tutorials/resources when learning JSP/HTML? Start at our JSP wiki page: stackoverflow.com/tags/jsp/info — BalusC

Esteban Aliverti Esteban Aliverti · Accepted Answer · 2012-11-01T20:13:24

The problem seems to be related to the fact that the class name is equal to the package name. There is a name clash since you are importing the package and you are also using the fqn of the class when invoking the display() method.

So, you imported HelloWorld.HelloWorld and then you try to do HelloWorld.HelloWorld.display(). Java is taking the first part of HelloWorld.HelloWorld.display as the class that you have imported and then tries to look for a static member called HelloWorld in that class.

Long story short, either remove the import (since you are using the fqn) or do not use the fqn when calling display().

Best Regards,

tomcat 7 shows compile error in a hello world jsp

1 Answers