CODEWITHSUNDEEP
javaeclipsevaadin7
TheLoneKing
TheLoneKing

Reputation: 235

Experiencing error while trying to load a Vaadin class

To begin with, today is my first day with Vaadin framework and I wanted to experiment with a Vaadin example. So, I have my example code in a java file called AddressbookUI.java in the com.example.addressbook package.

The example code is:

package com.example.addressbook;

import com.vaadin.annotations.Theme;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.Button;
import com.vaadin.ui.Button.ClickEvent;
import com.vaadin.ui.Label;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;

@SuppressWarnings("serial")
@Theme("addressbook")
public class AddressbookUI extends UI {

    public static class Servlet extends VaadinServlet {
    }

    @Override
    protected void init(VaadinRequest request) {
        final VerticalLayout layout = new VerticalLayout();
        layout.setMargin(true);
        setContent(layout);

        Button button = new Button("Click Me");
        button.addClickListener(new Button.ClickListener() {
            public void buttonClick(ClickEvent event) {
                layout.addComponent(new Label("Thank you for clicking"));
            }
        });
        layout.addComponent(button);
    }

}

My web.xml file contains the following.

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>AddressBook</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>

  <servlet>
    <servlet-name>ThankU</servlet-name>
    <servlet-class>com.example.addressbook.AddressbookUI</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ThankU</servlet-name>
    <url-pattern>/thanku</url-pattern>
  </servlet-mapping>

</web-app>

I am working on Eclipse 4.3 IDE and using Tomcat 7.0 for server. When I try to run my code, I get the following error:

HTTP Status 500 - Class com.example.addressbook.AddressbookUI is not a Servlet

type Exception report

message Class com.example.addressbook.AddressbookUI is not a Servlet

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

exception

javax.servlet.ServletException: Class com.example.addressbook.AddressbookUI is not a Servlet org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040) org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607) org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313) java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) java.lang.Thread.run(Unknown Source)

root cause

java.lang.ClassCastException: com.example.addressbook.AddressbookUI cannot be cast to javax.servlet.Servlet org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040) org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607) org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313) java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) java.lang.Thread.run(Unknown Source)

I couldn't understand what the problem is and I referred this SO question. I tried the solutions suggested there but with no improvement. There was no vaadin-xx.yy.zz.jar file in WEB-INF/lib. In fact, lib was empty.

What is wrong here and how can I resolve it?

Upvotes: 0

Views: 789

Answers (1)

Mise
Mise

Reputation: 3567

In the web.xml change by:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
    <display-name>Vaadin Web Application</display-name>
    <context-param>
       <description>Vaadin production mode</description>
       <param-name>productionMode</param-name>
       <param-value>false</param-value>
    </context-param>
    <servlet>
        <servlet-name>Vaadin</servlet-name>
        <servlet-class>com.vaadin.server.VaadinServlet</servlet-class>
        <init-param>
           <description>Vaadin UI to display</description>
           <param-name>UI</param-name>
           <param-value>com.example.addressbook.AddressbookUI</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>Vaadin</servlet-name>
        <url-pattern>/thanku</url-pattern>
    </servlet-mapping>
</web-app>

Upvotes: 2

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