JSP - Error instantiating servlet class [com.example.demo.HelloServlet]

Sahil Mambilly 0
Viewed 30

Getting started with JSP, still a begineer to Java though.

The error is as mentioned in the title. A few more lines from the error message:

*

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

Exception

javax.servlet.ServletException: Error instantiating servlet class [com.example.demo.HelloServlet]
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:360)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:890)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1789)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:833)
Root Cause

java.lang.NoClassDefFoundError: jakarta/servlet/http/HttpServlet
    java.base/java.lang.ClassLoader.defineClass1(Native Method)
    java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1013)
    java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
    org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:2472)
    org.apache.catalina.loader.WebappClassLoaderBase.findClass(WebappClassLoaderBase.java:875)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1376)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1220)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:360)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:890)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1789)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:833)
Root Cause

java.lang.ClassNotFoundException: jakarta.servlet.http.HttpServlet
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1412)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1220)
    java.base/java.lang.ClassLoader.defineClass1(Native Method)
    java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1013)
    java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
    org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:2472)
    org.apache.catalina.loader.WebappClassLoaderBase.findClass(WebappClassLoaderBase.java:875)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1376)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1220)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:360)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:890)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1789)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:833)
Note The full stack trace of the root cause is available in the server logs.

index.jsp

<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html>
<head>
    <title>JSP - Hello World</title>
</head>
<body>
<h1><%= "Hello World!" %>
</h1>
<br/>
<a href="hello-servlet">Hello Servlet</a>
</body>
</html>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee https://jakarta.ee/xml/ns/jakartaee/web-app_5_0.xsd"
         version="5.0">

    <servlet>
        <servlet-name>helloServlet</servlet-name>
        <servlet-class>com.example.demo.HelloServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>helloServlet</servlet-name>
        <url-pattern>/hello-servlet</url-pattern>
    </servlet-mapping>
</web-app>

HelloServlet.java

package com.example.demo;

import java.io.*;

import jakarta.servlet.http.*;
import jakarta.servlet.annotation.*;

@WebServlet(name = "helloServlet", value = "/hello-servlet", urlPatterns = {"/hello-servlet"}, loadOnStartup = 1)
public class HelloServlet extends HttpServlet {
    private String message;

    public HelloServlet(){

    }

    public void init() {
        message = "Hello World!";
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        response.setContentType("text/html");

        // Hello
        PrintWriter out = response.getWriter();
        out.println("<html><body>");
        out.println("<h1>" + message + "</h1>");
        out.println("</body></html>");
    }

    public void destroy() {
    }
}

I added the urlPatterns = ..., loadOnStartup in the @WebServlet used in the java file - after looking at some solutions on StackOverflow, but nothing seems to be working.

Project Structure

Any working solutions?

Tried adding a constructor to the Java class, edited the web.xml by adding the servlet tag, also the @WebServlet line in the java class, but nothing works.

Did everything keeping the project structure in mind, still no solution. Used only one web mapping - either @WebServlet or web.xml, doesnt work. Also used both, still doesn't work.

I am using IntelliJ ultimate edition.

jsp intellij-idea java
1 Answers

SOLVED!

There's a problem when trying to work with the latest Jakarta EE and Tomcat 9 server (which I was using at that time). The newer 10.0 version solves it.

Sahil Mambilly0
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