Servlet HTTP 500 error

[weeniejeff]

Group,

I'm getting an HTTP 500 Status error using Apache Tomcat. I'm
learning Servlets and JSPs from the Head First book. I've searched
the groups and on the Internet, and can't seem to resolve my problem.

I have a webpage, form.html, that displays just fine with http://
localhost:8080/beer-V1/form.html. This web page is mapped in web.xml
to /BeerSelect.do:

- <servlet>
<servlet-name>Ch3 Beer</servlet-name>
<servlet-class>com.example.web.BeerSelect</servlet-class>
</servlet>
- <servlet-mapping>
<servlet-name>Ch3 Beer</servlet-name>
<url-pattern>/SelectBeer.do</url-pattern>
</servlet-mapping>
</web-app>

BeerSelect.do maps the BeerSelect servlet class, which controls the
BeerExpert model.

BeerSelect:
package com.example.web;

import com.example.model.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;

public class BeerSelect extends HttpServlet {

public void doPost(HttpServletRequest request,
HttpServletResponse
response)
throws IOException, ServletException {

response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("Beer Selection Advice<br>");
String c = request.getParameter("color");

BeerExpert be = new BeerExpert();
List result = be.getBrands(c);
Iterator it = result.iterator();
while (it.hasNext()) {
out.println("<br>try: " + it.next());
}
} //end doPost

} //end class

is stored in C:\Apache\Tomcat6\webapps\beer-V1\WEB-INF\classes\com
\example\web\BeerSelect.class - it compiled just fine.

BeerExpert:
package com.example.model;
import java.util.*;

public class BeerExpert {

public List getBrands(String color) {
ArrayList<String> brands = new ArrayList<String>();
if (color.equals("amber")) {
brands.add("Jack Amber");
brands.add("Red Moose");
}
else {
brands.add("Jail Pale Ale");
brands.add("Gout Stout");
}
return(brands);
}

}

is stored in C:\Apache\Tomcat6\webapps\beer-V1\WEB-INF\classes\com
\example\model\BeerExpert.class, and it compiled just fine.

When I hit the submit button on form.html, I get this HTTP 500 error:
java.lang.NoClassDefFoundError: com/example/web/BeerSelect (wrong
name: BeerSelect)
java.lang.ClassLoader.defineClass1(Native Method)
java.lang.ClassLoader.defineClass(Unknown Source)
java.security.SecureClassLoader.defineClass(Unknown Source)

org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappCl
assLoader.java:1815)

org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoade
r.java:872)

org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoade
r.java:1325)

org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoade
r.java:1204)

org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.jav
a:105)

org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:
212)

org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:
844)
org.apache.coyote.http11.Http11Protocol
$Http11ConnectionHandler.process(Http11Protocol.java:634)
org.apache.tomcat.util.net.JIoEndpoint
$Worker.run(JIoEndpoint.java:
445)
java.lang.Thread.run(Unknown Source)

I'm not sure what's going on... I can't seem to find what I'm
configuring incorrectly. Could someone please help?

 

[yasminevw]

Group,

I'm getting an HTTP 500 Status error using Apache Tomcat. I'm
learning Servlets and JSPs from the Head First book. I've searched
the groups and on the Internet, and can't seem to resolve my problem.

I have a webpage, form.html, that displays just fine with http://
localhost:8080/beer-V1/form.html. This web page is mapped in web.xml
to /BeerSelect.do:

How does you're form.html look like? and how did you deploy the war
(web application) on you web server. Does it listen to a context-root?

From you url it looks like you're application is listing to the host

localhost at port 8080 and that you're using beer-V1 as a context
root, but if you type in the action "/BeerSelect.do" it looks for a
webapplication which listens to a web application a the '/' context
root.
Try to change the action in form.html to /beer-V1/BeerSelect.do.

The rest of you're code like ok to me.

 

[Daniel Pitts]

Group, [snip]
java.lang.NoClassDefFoundError: com/example/web/BeerSelect (wrong
name: BeerSelect)
java.lang.ClassLoader.defineClass1(Native Method)
java.lang.ClassLoader.defineClass(Unknown Source)
java.security.SecureClassLoader.defineClass(Unknown Source)
[snip]
I'm not sure what's going on... I can't seem to find what I'm
configuring incorrectly. Could someone please help?

It looks like somehow its finding the BeerSelect.class file, but the
class file doesn't have the right package name. Try deleting it and re-
compiling. It could be that you have an older class file, and it
wasn't compiled with the package declaration.

Hope this helps,
Daniel.

 

[Nigel Wade]

Group, [snip]
java.lang.NoClassDefFoundError: com/example/web/BeerSelect (wrong
name: BeerSelect)
java.lang.ClassLoader.defineClass1(Native Method)
java.lang.ClassLoader.defineClass(Unknown Source)
java.security.SecureClassLoader.defineClass(Unknown Source)
[snip]
I'm not sure what's going on... I can't seem to find what I'm
configuring incorrectly. Could someone please help?

It looks like somehow its finding the BeerSelect.class file, but the
class file doesn't have the right package name. Try deleting it and re-
compiling. It could be that you have an older class file, and it
wasn't compiled with the package declaration.

Hope this helps,
Daniel.

and to the OP, do not multi-post. I've just wasted my time giving pretty much
exactly the same answer as this in another group to which the question was
multi-posted.

 

[rbeins]

use this
<servlet>
<servlet-name>SelectBeer</servlet-name>
<servlet-class>BeerSelect</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>SelectBeer</servlet-name>
<url-pattern>/SelectBeer.do</url-pattern>
</servlet-mapping>

 

[rbeins]

use this

<servlet>
<servlet-name>SelectBeer</servlet-name>
<servlet-class>BeerSelect</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>SelectBeer</servlet-name>
<url-pattern>/SelectBeer.do</url-pattern>
</servlet-mapping>