I need a logout servlet for this. Any help?

Java Code: 
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;


 //This Servlet logs in a user



public class Servlet_login extends HttpServlet {

	private HttpSession session;

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {

		response.setContentType("text/html; charset=ISO-8859-7");
		PrintWriter out = new PrintWriter(response.getWriter(), true);

	    //Enable Session

		session = request.getSession(true);


		// Gets username and password from html form

		String username = request.getParameter("username");
		String password = request.getParameter("password");

		User myUser=null;

		try {


			 //Checks if user has filled all the necessary fields. If
			 //not forwards the request to the ErrorHandlerServlet

			if (!(username.length() > 0) || !(password.length() > 0)) {

				request.setAttribute("error_id", "emptyLogin");
				RequestDispatcher dispatcher1 = getServletContext()
				.getRequestDispatcher("/servlet/ErrorHandlerServlet");
				dispatcher1.forward(request, response);
				return;
			}



		   //Initializes new User Object.

			myUser = new User(username, password);


			 //Checks if data given by user is right to log him in. If
			 //not forwards the request to the ErrorHandlerServlet

			if (!myUser.LoginUser()) {

				request.setAttribute("error_id", "wrongLogin");
				RequestDispatcher dispatcher1 = getServletContext()
				.getRequestDispatcher("/servlet/ErrorHandlerServlet");
				dispatcher1.forward(request, response);
				return;
			}


			//set login status and customer's data to session

			session.setAttribute("login1", username);
			session.setAttribute("login2", password);

		   //HTML
			out.println("<html>");
			out.println("</html>");



//Exception

		} catch (Exception ex) {

		
			request.setAttribute("error_id", ex.getMessage()+" - "+myUser.getErrorMessages()) ;
			RequestDispatcher dispatcher1 = getServletContext()
			.getRequestDispatcher("/servlet/ErrorHandlerServlet");
			dispatcher1.forward(request, response);
			return;
		}
	}

   /*
	* Checks if there is a logged-in user
	*/
	private boolean checkSessionLogin() {

		try {
			String loginStatus = session.getAttribute("login").toString();
			if (loginStatus.equals("login is ok"))
				return true;
			else
				return false;
		} catch (NullPointerException e) {
			return false;
		}
	}

   /*
	* Returns from the session the username of the logged-in user
	*/
	private String getUsername() {

		try {
			User user = (User) session.getAttribute("User");
			if (user.getUsername().length()>0)
				return user.getUsername();
			else
				return "no Logged-in user" ;
			} catch (NullPointerException e) {
			return null ;
		}
	}



}