public class DbClass extends HttpServlet{
  
  public static Connection getConnect(HttpServletRequest request) throws ServletException, IOException {
    
    Connection conn = null;
    
    String db_host = request.getServletContext().getInitParameter("db_host"),
            db_port = request.getServletContext().getInitParameter("db_port"),
            db_name = request.getServletContext().getInitParameter("db_name"),
            db_login = request.getServletContext().getInitParameter("db_login"),
            db_password = request.getServletContext().getInitParameter("db_password"),
            db_driver = request.getServletContext().getInitParameter("db_driver"),
            db_engine = request.getServletContext().getInitParameter("db_engine"),
            db_url = "jdbc:"+db_engine+"://"+db_host+":"+db_port+"/"+db_name+"?user="+db_login+"&password="+db_password;
    
    try {
      Class.forName(db_driver).newInstance();
      conn = DriverManager.getConnection(db_url);
    } catch(Exception e) {
      //
    }
    
    return conn;
  }
  
}

exception

javax.servlet.ServletException: Servlet execution threw an exception
root cause

java.lang.NoSuchMethodError: method javax.servlet.http.HttpServletRequest.getServletContext with signature ()Ljavax.servlet.ServletContext; was not found.
	my.DbClass.getConnect(DbClass.java:24)
	controller.TendersServlet.processRequest(TendersServlet.java:40)
	controller.TendersServlet.doGet(TendersServlet.java:123)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

<web-app 
  version="2.5" 
  xmlns="http://java.sun.com/xml/ns/javaee" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
>