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ClassNotFoundException - How to use external libraries without maven?

As a result of my previous question I followed these steps to include Apache PDFbox without maven:
downloaded .jars from download site of PDFbox (all under Libraries of each subproject)
downloaded .jars from dependencies of PDFbox from maven repository (commons-logging and fontbox, but fontbox was already included in step 1)
placed the downloaded .jars in a folder (C:\PDFjars)
configured build path in eclispe (added all .jars as external libraries) It now looks like this:
My servlet:
package servlets;
// other imports
import org.apache.pdfbox.pdmodel.PDDocument;
#WebServlet("/print")
public class PrintServlet extends HttpServlet {
public PrintServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// From a PDFbox Tutorial
//Creating PDF document object
PDDocument document = new PDDocument();
//Saving the document
document.save("C:/PdfBox_Examples/my_doc.pdf");
System.out.println("PDF created");
//Closing the document
document.close();
doGet(request, response);
}
}
So when I start my web project and call the function the should produce a simple PDF document, I get folloing error:
Servlet.service() for servlet [servlets.PrintServlet] in context with path [/StaticsCalculator] threw exception [Servlet execution threw an exception] with root cause
java.lang.ClassNotFoundException: org.apache.pdfbox.pdmodel.PDDocument
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1291)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1119)
at servlets.PrintServlet.doPost(PrintServlet.java:44)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
Solution: I had to copy the .jars in WEB-INF/lib folder as well.

Download the jar file by itself and add it to your code dependency. You can search for any Maven file on Maven Repository. If you're using Eclipse, just modify the build path to point to an external jar and give it the location of your jar. This will not take care of any dependencies your library requires, which leads into dependency hell where you'll have to read the pom and download each library manually.

You can
a) use a local maven repository and place the dependencies there.
b) add the dependencies in the classpath of the application - that's basically what maven does for you.

Error 505 on servlet request [duplicate]

This question already has an answer here:
Eclipse does not seem to compile servlet, causing java.lang.ClassNotFoundException
(1 answer)
Closed 5 years ago.
I'm trying to make a simple form but I get an error 500
index.php
<html>
<body>
<form action="login">
<input type="text" name="nombre"></input>
<input type="submit" value="Enviar"></input>
</form>
</body>
</html>
LoginServlet.java
package com.prueba1;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class LoginServlet
*/
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* Default constructor.
*/
public LoginServlet() {
// TODO Auto-generated constructor stub
}
/**
* #see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.getWriter().append("Served at: ").append(request.getContextPath());
}
/**
* #see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
web.xml
<!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>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<display-name>LoginServlet</display-name>
<description></description>
<servlet-class>com.prueba1.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
</web-app>
The urlpatter is set as /login and the form action is login but when I try to submit , I get an 505 error, there is no error on code and I don't know whats the problem.I've followed many tutorials and always get the same error.
this is the error , the servlet class is not found
javax.servlet.ServletException: Error instanciando clase de servlet [com.prueba1.LoginServlet]
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1457)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:748)
causa raíz
java.lang.ClassNotFoundException: com.prueba1.LoginServlet
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1285)
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1119)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1457)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:748)
Project tree image:

Just tried to deploy and run your code on my own computer and it worked well. Make sure that your project structure is valid, you included your LoginServlet.java file into project right and that LoginServlet.class file is at the right directory after compilation. This is my project stucture:
Make sure your class is at WEB-INF/classes
link to screenshot
If you can't solve the problem, you should show your project structure after compilation. Maybe I can help you, if my screenshot will not help you. Don't forget that I'm using Maven to build the project. You structure may be a bit different.
If you are using Maven add the following lines into the dependencies block of pom.xml file:
`
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.0</version>
<scope>provided</scope>
</dependency>
`
If not, just try to add the following line before the class declaration block:
#WebServlet(name="any name you want", urlPatterns="/login")

Exception when forwarding request to servlet in Java web application

I have a problem and I don't know how to solve it.
My web application MyApp is a Maven web application project (Java 8 and Java EE 5). To run an updated version as test instance on the same server, I changed the Context Path of the application from MyApp to MyAppTest. As servlet container, I'm using Tomcat 8.
The MyApp instance is working as expected. However the MyAppTest instance is throwing an exception when forwarding the request to one of my servlets. Even if MyApp and MyAppTest are identical except the context path, this exception occurs. The Servlets are mapped via Guice's ServletModule.
Message:
java.lang.StringIndexOutOfBoundsException: String index out of range: -4
StackTrace:
java.lang.String.substring(Unknown Source)
com.google.inject.servlet.ServletDefinition$2.getPathInfo(ServletDefinition.java:212)
org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:376)
org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:318)
myapp.base.MainEntryServlet.service(MainEntryServlet.java:49)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
com.google.inject.servlet.ServletDefinition.doServiceImpl(ServletDefinition.java:286)
com.google.inject.servlet.ServletDefinition.doService(ServletDefinition.java:276)
com.google.inject.servlet.ManagedServletPipeline$1.doServiceImpl(ManagedServletPipeline.java:154)
com.google.inject.servlet.ManagedServletPipeline$1.forward(ManagedServletPipeline.java:140)
myapp.auth.LogoutServlet.service(LogoutServlet.java:57)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
com.google.inject.servlet.ServletDefinition.doServiceImpl(ServletDefinition.java:286)
com.google.inject.servlet.ServletDefinition.doService(ServletDefinition.java:276)
com.google.inject.servlet.ServletDefinition.service(ServletDefinition.java:181)
com.google.inject.servlet.ManagedServletPipeline.service(ManagedServletPipeline.java:91)
com.google.inject.servlet.FilterChainInvocation.doFilter(FilterChainInvocation.java:85)
com.google.inject.servlet.ManagedFilterPipeline.dispatch(ManagedFilterPipeline.java:120)
com.google.inject.servlet.GuiceFilter.doFilter(GuiceFilter.java:135)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528)
org.apache.coyote.ajp.AbstractAjpProcessor.process(AbstractAjpProcessor.java:873)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:670)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1520)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1476)
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Unknown Source)
The Servlet forwarding the Request does this:
RequestDispatcher dispatcher = request.getRequestDispatcher("/index.jsp");
if (!response.isCommitted()) {
dispatcher.forward(request, response);
}
The URL index.jsp is mapped to another Servlet. It forwards the request to a JSP:
request.getRequestDispatcher("/theme/index.jsp").forward(request, response);
There the exception occurs. Some other JSPs are included into the index.jsp like this:
<jsp:include flush="true" page="menu.jsp"/>
The menu.jsp is located in the same folder as the index.jsp.
As mentioned before, everything works fine as long as the Context path is MyApp. When changed to MyAppTest the exception occurs. It must have something to do with the Context path itself. When changing the Path to MyAppTest, the exception message is "String index out of range: -4". When I change the Path to MyAppTesting, the exception message changes to "String index out of range: -7".
To solve this I tried the following:
Changing the Context path and the docBase to MyAppTest in the context.xml of the project.
Changing the Artifact ID of the project to MyAppTest.
Changing the Project Name to MyAppTest.
Nothing worked. And I don't know what causes the exeption: Maven, Tomcat or Guice.

Unable to instantiate a servlet, getting class not found exception

I have created a sample maven project using the following command:
mvn archetype:generate -DgroupId=com.rohit -DartifactId=RohitLoginApp -DarchetypeArtifactId=maven-archetype-webapp -DinteractiveMode=false
Below is the image link of the project structure in eclipse:
Maven project structure in eclipse
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.rohit</groupId>
<artifactId>RohitLoginApp</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>RohitLoginApp Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.0.1</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<finalName>RohitLoginApp</finalName>
</build>
</project>
web.xml:
<!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>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>RohitTestServlet</servlet-name>
<display-name>RohitTestServlet</display-name>
<description></description>
<servlet-class>com.company.rohit.RohitTestServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>RohitTestServlet</servlet-name>
<url-pattern>/RohitTestServlet</url-pattern>
</servlet-mapping>
</web-app>
RohitTestServlet.java
package com.company.rohit;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class RohitTestServlet
*/
public class RohitTestServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* #see HttpServlet#HttpServlet()
*/
public RohitTestServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* #see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String userId = request.getParametker("userName");
String pwd = request.getParametker("psw");
response.getWriter().write("User ID and password are received");
}
/**
* #see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
}
Index.jsp
<html>
<body>
<h2>Login Page</h2>
<form action="RohitTestServlet">
User Name<br>
<input type="text" name="userName">
<br>
Password<br>
<input type="password" name="psw">
<br><br>
<input type="submit" value="Submit">
</form>
</body>
</html>
When I deploy this app on tomcat, it first loads the welcome screen where I enter the userID and password and click on submit button. Then it redirects to servlet url i.e. http://localhost:8080/RohitLoginApp/RohitTestServlet?userName="xyz"&psw="www". However its unable to hit the servlet and get the response. Below is the error:
SEVERE: Allocate exception for servlet RohitTestServlet
java.lang.ClassNotFoundException: com.company.rohit.RohitTestServlet
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1856)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1705)
at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:506)
at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:488)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:115)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1148)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:864)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:134)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
It is unable to load the class. I had done clean build lot of times but still its unable to load the servlet.

It looks like your class is not being compiled into the war file. You need to make sure your servlet class is defined in src/main/java with the appropriate package subfolders. You can verify this by going to webapps directory and looking in the "classes" folder to see if your class is there.

SEVERE: Allocate exception for servlet, error when trying to call a servlet from JSP page

When I run the jsp on the tomcat server and it runs ok, but when I click submit it throws the following error, I have checked over everything and I am not sure where to go from here because it seems like it should work, any help would be much appreciated, Thank you.
Error Stack Trace:
SEVERE: Allocate exception for servlet RegistrationServlet
java.lang.ClassNotFoundException: logon.RegistrationServlet.java
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1720)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:529)
at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:511)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:139)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1148)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:864)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:134)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:315)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
web.xml
<?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"
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>RegistrationTest</display-name>
<servlet>
<display-name>RegistrationServlet</display-name>
<servlet-name>RegistrationServlet</servlet-name>
<servlet-class>logon.RegistrationServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>RegistrationServlet</servlet-name>
<url-pattern>/RegistrationServlet</url-pattern>
</servlet-mapping>
</web-app>
The JSP page:
<h2>Signup Details</h2>
<form name="actionForm" action="RegistrationServlet" method ="post">
<br/>Username:<input type="text" name="name">
<br/>Password:<input type="password" name="password">
<br/>Email:<input type="text" name="email">
<br/><input type="submit" value="Submit">
</form>
The Servlet:
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class RegistrationServlet
*/
#WebServlet("/RegistrationServlet")
public class RegistrationServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public RegistrationServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try{
System.out.println("In the registration Servlet");
User user = new User();
user.setName(request.getParameter("name"));
user.setPassword(request.getParameter("password"));
user.setEmail(request.getParameter("email"));
RegisterUser.addUser(user);
//response.sendRedirect("welcome.jsp");
} catch (Throwable exc)
{
System.out.println(exc);
}
}
}

For anybody that has a similar problem in the future, after cleaning the project, ensure that the build automatically box is checked under the project drop down menu as this is required to rebuild after clean, mine was unchecked by default for some reason.
Also I made a small error in the code, I used annotations (#webservlet) in my servlet and I also added the servlet to my web.xml which caused a conflict. This is now done automatically with annotations.

I also got the same exception and resolved just by putting full qualified calssname in the web.xml fle.
$fully qualified class name$