[FIXED] Load Java class when starting Tomcat

Issue

I am trying to read a java class as soon as I run the project on tomcat, but I get the java class error not found exception

<?xml version="1.0" encoding="ISO-8859-1"?>

<!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>

<listener>
    <listener-class>
        Bot.CarregarBot
    </listener-class>
</listener>


</web-app>

The class I want to load when I run the project is the Bot.CarregarBot class;

When I run the project and the server is started, I get the following error:

GRAVE: Error configuring application listener of class [Bot.CarregarBot]
java.lang.ClassNotFoundException: Bot.CarregarBot
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1365)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1188)
    at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:540)
    at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:521)
    at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:150)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4607)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5146)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:841)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)

class CarregarBot.java

package Bot;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

    public class CarregarBot implements ServletContextListener {
        String action;
        String requestA;
        String responseA;
        org.alicebot.ab.Bot bot;

        @Override
        public void contextInitialized(ServletContextEvent servletContextEvent) {
            System.out.println("Starting up!");
            org.alicebot.ab.MagicStrings.setRootPath();
            org.alicebot.ab.AIMLProcessor.extension =  new org.alicebot.ab.PCAIMLProcessorExtension();
            String botName = "alice2";
            action = "chat";
            bot = new org.alicebot.ab.Bot(botName, org.alicebot.ab.MagicStrings.root_path, action); 


            System.out.println("--- Carregou Classe ---");      
        }

        @Override
        public void contextDestroyed(ServletContextEvent servletContextEvent) {
            System.out.println("Shutting down!");
        }
    }

Solution

Generally in a typical java web application (war) structure - the compiled class files should end up in WEB-INF/classes folder ( unless they can be archived as a jar then they can be out in WEB-INF/lib as well). So try changing your project's build path to <your-project>/WebContent/WEB-INF/classes. You can refer to the below screen shot attached Here is class I have tried to use and the output on the console when I start my server

package Bot;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

/**
 * Application Lifecycle Listener implementation class CarregarBot
 *
 */

public class CarregarBot implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent event) {
        System.out.println("CarregarBot initialized");
    }

    @Override
    public void contextDestroyed(ServletContextEvent event) {

    }

}

Console output

Aug 27, 2019 1:22:47 AM org.apache.catalina.core.StandardContext reload
INFO: Reloading Context with name [/TestWebApp] has started
CarregarBot initialized
Aug 27, 2019 1:22:47 AM org.apache.catalina.core.StandardContext reload
INFO: Reloading Context with name [/TestWebApp] is completed

Answered By - Shailendra
Answer Checked By - Willingham (JavaFixing Volunteer)