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Error in web.xml file when I add context-parameters to it

I am getting an error in web.xml file while adding context parameters to it.
Here is web.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">
<context-param>
<pram-name>ADMIN_PATH</param-name>
<param-value>AdminChatServlet</param-value>
</context-param>
<context-param>
<param-name>ROOMLIST_PATH</param-name>
<param-value>/RoomListServlet</param-value>
</context-param>
<context-param>
<param-name>CHROOM_PATH</param-name>
<param-value>/ChRoomServlet</param-value>
</context-param>
<servlet>
<servlet-name>MainChatServlet</servlet-name>
<servlet-class>MainChatServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>AdminChatServlet</servlet-name>
<servlet-class>AdminChatServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>RoomListServlet</servlet-name>
<servlet-class>RoomListServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>ChRoomServlet</servlet-name>
<servlet-class>ChRoomServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>MainChatServlet</servlet-name>
<url-pattern>/MainChatServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>AdminChatServlet</servlet-name>
<url-pattern>/AdminChatServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>RoomListServlet</servlet-name>
<url-pattern>/RoomListServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ChRoomServlet</servlet-name>
<url-pattern>/ChRoomServlet</url-pattern>
</servlet-mapping>
<session-config>
<session-timeout>30</session-timeout>
</session-config>
</web-app>
and here is the servlet(MainChatServlet) using those context-parameters:
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.util.*;
import com.amir.*;
public class MainChatServlet extends HttpServlet {
String chRoomPath;//="ChRoomServlet.java";
String roomListPath;//="RoomListServlet.java";
String adminChatPath;//="AdminChatServlet.java";
public void init()
{
ServletContext context = getServletConfig().getServletContext();
context.setAttribute("chRoomPath",context.getInitParameter("CHROOM_PATH"));
context.setAttribute("roomListPath",context.getInitParameter("ROOMLIST_PATH"));
context.setAttribute("adminChatPath",context.getInitParameter("ADMINCHAT_PATH"));
}
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
HttpSession session = request.getSession();
chRoomPath = (String)getServletContext().getAttribute("chRoomPath");
roomListPath = (String)getServletContext().getAttribute("roomListpath");
adminChatPath = (String)getServletContext().getAttribute("adminChatPath");
session.setAttribute("chRoomPath",chRoomPath);
session.setAttribute("roomListPath", roomListPath);
session.setAttribute("adminChatPath",adminChatPath);
HashMap hashmap = null;
try
{
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/chat","root","mysql");
synchronized(getServletContext())
{
hashmap = (HashMap)getServletContext().getAttribute("chatList");
if(hashmap == null)
{
hashmap =new HashMap();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("select * from chatrooms");
while(rs.next())
{
hashmap.put(rs.getString(1),new ChatRoom(rs.getString(1),rs.getString(2),4));
}
rs.close();
getServletContext().setAttribute("roomList", hashmap);
}
}
conn.close();
}
catch(ClassNotFoundException e)
{
System.out.print("Error(Class)");
e.printStackTrace();
}
catch(SQLException e)
{
System.out.print("Error(SQL)");
e.printStackTrace();
}
RequestDispatcher view = request.getRequestDispatcher("chat.jsp");
view.forward(request, response);
}
}
and here is the default-package in which all the .java files(servlets are kept)
Screenshot#1
Why am I getting the error in the web.xml file?
Screenshot#2
EDIT: OR Suggest me any alternate idea if possible.

javax.servlet.UnavailableException: SRVE0200E - Maven webapp

I am trying to deploy a single maven webapp on a Websphere Liberty Server.
My code (XCCQuery.java):
package TTAQuery;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.ws.rs.core.Response;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.core.Response;
#WebServlet(name="XCCQuery", urlPatterns={"/hello"})
public class XCCQuery extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = response.getWriter();
String simpleParam = getServletConfig().getInitParameter("simpleParam");
out.println("Hello World "+simpleParam);
out.close();
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
My web.xml looks like this:
<!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>XCCQuery</servlet-name>
<display-name>XCCQuery</display-name>
<description></description>
<servlet-class>XCCQuery</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>XCCQuery</servlet-name>
<url-pattern>/rest/*</url-pattern>
</servlet-mapping>
</web-app>
I try to access:
http://localhost:9087/XCCQueryServlet/rest/hello
but always get:
Error 404: javax.servlet.UnavailableException: SRVE0200E: Servlet [XCCQuery]: Could not find required class - XCCQuery
Seems to be a deployment mistake for me.
What's wrong here?

Url doesn't match url-pattern in web.xml

In the web.xml file I have this url pattern:
<url-pattern>/servletPrueba/*</url-pattern>
and in the jsp file I have this link:
Enlace servlet
But I get a 404 error, I think the url matches the url pattern, doesn't it?
here is the servlet,it's onle a test purposes servlet,only for practice
package pruebas;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.RequestDispatcher;
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 servletPrueba
*/
//#WebServlet("/servletPrueba")
public class servletPrueba extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* #see HttpServlet#HttpServlet()
*/
public servletPrueba() {
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
//response.getWriter().append("Served at: ").append(request.getContextPath());
RequestDispatcher despachador = null;
String ruta = request.getPathInfo();
PrintWriter out = response.getWriter();
out.println(request.getPathInfo());
out.println(request.getServletPath());
}
/**
* #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);
PrintWriter out = response.getWriter();
out.println("POST");
}
}
webb.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
<display-name>pruebas</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>servletPrueba</servlet-name>
<servlet-class>pruebas.servletPrueba</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>servletPrueba</servlet-name>
<url-pattern>/servletPrueba/*</url-pattern>
</servlet-mapping>
</web-app>

Here is a complete example (I did not use Maven, however I could) :

HTTP Status 404 - Not Found [duplicate]

This question already has answers here:
Servlet returns "HTTP Status 404 The requested resource (/servlet) is not available"
(19 answers)
Closed 6 years ago.
filter
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.*;
public class MyFilter implements Filter{
#Override
public void init(FilterConfig arg0) throws ServletException {}
#Override
public void doFilter(ServletRequest req, ServletResponse resp,
FilterChain chain) throws IOException, ServletException {
PrintWriter out=resp.getWriter();
out.print("filter is invoked before");
chain.doFilter(req, resp);//sends request to next resource
out.print("filter is invoked after");
}
public void destroy() {}
}
servlet
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.*;
public class HelloServlet extends HttpServlet {
#Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.print("<br>welcome to servlet<br>");
}
}
web.xml
<web-app>
<servlet>
<servlet-name>HelloServlet</servlet-name>
<servlet-class>HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloServlet</servlet-name>
<url-pattern>/HelloServlet</url-pattern>
</servlet-mapping>
<filter>
<filter-name>MyFilter</filter-name>
<filter-class>MyFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>MyFilter</filter-name>
<url-pattern>/servlet1</url-pattern>
</filter-mapping>
</web-app>
index.html
click here
error is :
HTTP Status 404 - Not Found
type Status report
messageNot Found
descriptionThe requested resource is not available.
GlassFish Server Open Source Edition 4.0
I have given entire code plz help me find my error
in am new to sevlet
question may sound dumb but plz help me

HTTP Status 404 - Not Found
because your servlet is mapped to /HelloServlet and your filter is trying to intercept servlet1 . since there is no servlet at servlet1 , container says no resource found.
change your filter mapping to /HelloServlet and click here.

Try to change this:
click here
With:
click here

Counting the number of users in web App in servlet

I have modified my application to find out the number of users logged in a web application below is my piece of code..
the listener class
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class SessionCounter implements HttpSessionListener
{
private static int count;
public static int getActiveSessions() {
return count;
}
public SessionCounter()
{
}
//The "sessionCount" attribute which has been set in the servletContext should not be modified in any other part of the application.
//Since we are using serveltContext in both the methods to modify the same variable, we have synchronized it for consistency.
public void sessionCreated(HttpSessionEvent e)
{
count++;
ServletContext sContext = e.getSession().getServletContext();
synchronized (sContext)
{
sContext.setAttribute("sessionCount", new Integer(count));
}
}
public void sessionDestroyed(HttpSessionEvent e)
{
count--;
ServletContext sContext = e.getSession().getServletContext();
synchronized (sContext)
{
sContext.setAttribute("sessionCount", new Integer(count));
}
}
}
and the main servlet is ..
package com.saral;
import java.io.IOException;
import org.apache.log4j.Logger;
import org.apache.log4j.PropertyConfigurator;
import java.io.PrintWriter;
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 First
*/
//#WebServlet("/First")
public class MyServlet extends HttpServlet
{
private static final long serialVersionUID = 1L;
static final Logger logger = Logger.getLogger(MyServlet.class);
/**
* #see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PropertyConfigurator.configure("log4j.properties");
logger.info("before---->");
// TODO Auto-generated method stub
String name=request.getParameter("txtName");
response.setContentType("text/html");
PrintWriter out=response.getWriter();
out.println("Hello,"+name);
out.println("<br> this output is generated by a simple servlet.");
out.println("Total Number of users logged in--->"+SessionCounter.getActiveSessions());
out.close();
}
}
and the web.xml is ...
<?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_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>FirstDemo</display-name>
<context-param>
<param-name>log4jConfigLocation</param-name>
<param-value>/WEB-INF/log4j.properties</param-value>
</context-param>
<servlet>
<servlet-name>hello</servlet-name>
<servlet-class>com.saral.MyServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/helloServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>home.html</welcome-file>
</welcome-file-list>
<listener>
<listener-class>com.saral.SessionCounter</listener-class>
</listener>
</web-app>
but I am getting the total number of users logged in as 0 , which is not perfect, please advise where I am wrong and how can I overcome from this.

When a client request come to the Tomcat server and you don't call request.getSession(), then the Tomcat server stil creates a session automatically. After that, the method sessionCreated(...) in your SessionCounter class is called.
The method sessionDestroyed(...) will be called when a session is destroyed. That occurs when you call session.invalidate(). If you close a tab on browser or close a browser, the session is still alive on your tomcat server.
I think so. You can use some diffrent listeners to archive your goal: HttpSessionAttributeListener, HttpSessionBindingListener,...