The requested resource is not available using HelloWorld servlet

I am writing a Java Servlet, and I am struggling to get a simple HelloWorld example to work properly.

Error 404: The requested resource is not available using HelloWorld servlet

The HelloWorld.java class is:

package crunch;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class HelloWorld extends HttpServlet {
  public void doGet(HttpServletRequest request,
                    HttpServletResponse response)
      throws ServletException, IOException {
    PrintWriter out = response.getWriter();
    out.println("Hello World");
  }
}

I am running Tomcat v7.0, and I have already read similar questions with responses referring to changing the servlet-mapping section in web.xml. This section actually doesn't exist in mine, and when I added it the same problem still occurred.

Try this (if the Java EE V6)

package crunch;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

@WebServlet(name="hello",urlPatterns={"/hello"}) // added this line

public class HelloWorld extends HttpServlet {
  public void doGet(HttpServletRequest request,
                    HttpServletResponse response)
      throws ServletException, IOException {
    PrintWriter out = response.getWriter();
    out.println("Hello World");
  }
}

now reach the servlet by http://127.0.0.1:8080/yourapp/hello

where 8080 is default Tomcat port, and yourapp is the context name of your applciation