Call doGet in the Init of a servlet?

Question

Hello
Please could you show through the code. I think there is something wrong with the init. If I run the servlet, it don't show a thing. It only displays: Site can't not be shown.
The doGet and also the dopost is not executed. Must I call in the doPost in the init(). And when yes how?
Thanks a lot!
Sandra Frei
import java.sql.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.Properties;
public class update42 extends HttpServlet {
     Connection con = null;
     public void init() {//throws ServletException {
          String url = "jdbc:DBF:/sys:copal/copal_data/data/gesch/data/stamm";      
          try {
               //Register the JDBC driver
               Class.forName("zyh.sql.dbf.DBFDriver");//.newInstance();
               con = DriverManager.getConnection(url, "fre","sandy66");                    
          catch( Exception e ) {
               e.printStackTrace();
          }//end catch
     }//end init()
     public void doGet(HttpServletRequest req, HttpServletResponse res)
          throws ServletException, IOException {
          res.setContentType("text/html");
          PrintWriter out = res.getWriter();
          out.print("in do get");
          //connecting to the Database
          Statement stmt = null;
          ResultSet rs = null;
          PreparedStatement ps = null;
               try
               stmt = con.createStatement();
               catch (SQLException e) {e.getNextException();}                              
               // displaying records
               try
               rs = stmt.executeQuery("SELECT Random, Nsa, Bzng, Bzn2, Tart, Meeh, Fstat, Nzn FROM part");
               catch (SQLException e) {e.getNextException();}                              
               try
               while(rs.next()) {
                    out.print("<form action=\"");
                    out.print( req.getRequestURI() );
                    out.print("\" method=\"post\">");
                    out.print("<input type=\"text\""); //hidden
                    out.print(" name=\"Random\" size=\"15\" value=\"");//without 15
                    out.print( rs.getObject(1).toString() );
                    out.print("\">");
                    out.print("<input type=\"text\"");
                    out.print(" name=\"Nsa\" size=\"15\" value=\"");
                    out.print( rs.getObject(2).toString() );
                    out.print("\">");
                    out.print("<input type=\"text\"");
                    out.print(" name=\"Bzng\" size=\"25\" value=\"");
                    out.print( rs.getObject(3).toString() );
                    out.print("\">");
                    out.print("<input type=\"text\"");
                    out.print(" name=\"Bzn2\" size=\"25\" value=\"");
                    out.print( rs.getObject(4).toString() );
                    out.print("\">");
                    out.print("<input type=\"text\"");
                    out.print(" name=\"Tart\" size=\"6\" value=\"");
                    out.print( rs.getObject(5).toString() );
                    out.print("\">");
                    out.print("<input type=\"text\"");
                    out.print(" name=\"Meeh\" size=\"6\" value=\"");
                    out.print( rs.getObject(6).toString() );
                    out.print("\">");
                    out.print("<input type=\"text\"");
                    out.print(" name=\"Fstat\" size=\"6\" value=\"");
                    out.print( rs.getObject(7).toString() );
                    out.print("\">");
                    out.print("<input type=\"text\"");
                    out.print(" name=\"Nzn\" size=\"15\" value=\"");
                    out.print( rs.getObject(8).toString() );
                    out.print("\">");
                    out.print(" <input type=\"submit\"");
                    out.print(" value=\" \">");
                    out.print(" Update<br>");
                    out.print("</form>");
               catch (SQLException e) {e.getNextException();}                              
               try
                    if(rs != null)
                         rs.close();
                    if(stmt != null)
                         stmt.close();
               catch (SQLException e) {
                    e.printStackTrace();
     out.print("</pre></code>");
     out.print("<p\"><a href=\"");
     out.print( req.getRequestURI() );
     out.print("\">Back</a></p>");
     out.print("</body></html>");
     out.close();
     public void doPost(HttpServletRequest req, HttpServletResponse res)
          throws ServletException, IOException {
          res.setContentType("text/html");
          PrintWriter out = res.getWriter();
          out.print("<html><body>");
          out.print("<code><pre>");
          out.print("<table border=1>");
     out.print("<tr>");
          out.print("<td><font color=green>Artikelnr</font></td>");
          out.print("<td><font color=green>Bezeichnung</font></td>");
          out.print("<td><font color=green>Zusatzbezeichnung</font></td>");
          out.print("<td><font color=green>Art</font></td>");
          out.print("<td><font color=green>ME</font></td>");
          out.print("<td><font color=green>Stat</font></td>");
          out.print("<td><font color=green>Spezifikation</font></td>");
     out.print("</tr>");
          // receiving parameters
          String Bzn2 = req.getParameter("Bzn2").trim();
          String Meeh= req.getParameter("Meeh").trim();
          String Pk = req.getParameter("Random").trim();
          boolean proceed = false;
          Statement stmt = null;
          Statement stmt1 = null;
          ResultSet rs = null;
          try {
               String sql;
          sql = "UPDATE part SET Bzn2 = " + "'" + Bzn2 + "'" + " WHERE Random LIKE " + "'" + Pk + "'";
               stmt1 = con.createStatement();               
               out.print(sql);
               out.print(Bzn2 + Meeh + Pk);
               stmt1.executeUpdate(sql);
          // displaying records
               stmt = con.createStatement();               
               rs = stmt.executeQuery("SELECT * FROM part");
               while(rs.next())
                    out.print("<tr>");
                    out.print("<td>"+ rs.getObject(1).toString()+ "</td>");
                    out.print("<td>"+ rs.getObject(2).toString()+ "</td>");
                    out.print("<td>"+ rs.getObject(3).toString()+ "</td>");
                    out.print("<td>"+ rs.getObject(4).toString()+ "</td>");
                    out.print("<td>"+ rs.getObject(5).toString()+ "</td>");
                    out.print("<td>"+ rs.getObject(6).toString()+ "</td>");
                    out.print("<td>"+ rs.getObject(7).toString()+ "</td>");
                    out.print("</tr>");
               out.print("</table>");
          catch (Exception e)     
               out.print(e.getMessage());
               e.printStackTrace();
               try
                    if(rs != null)
                         rs.close();
                    if(stmt != null)
                         stmt.close();
                    if(stmt1 != null)
                         stmt1.close();
               catch (SQLException e) {e.getNextException();}
          out.print("</pre></code>");
          out.print("<p\"><a href=\"");
          out.print( req.getRequestURI() );
          out.print("\">Back</a></p>");
          out.print("</body></html>");
          out.close();
     public void destroy() {
          try {
               //Close the connection to the database
               con.close();
          } catch( Exception e ) {
               e.printStackTrace();
}

Answer 1

It won't get shown unless you make a call to the servlet from (e.g.) a web browser referencing it. And no - don't call doPost() or doGet() from the init() method. You might be lucky, and it might work, but it's inherently unsafe. Servlet engines will not normally call these methods until the servlet is properly initialised.
And BTW, there is no guarantee that init() will be called until the first call to the servlet, unless you specify load on startup to the servlet engine.
Your best bet is simply to type the URL of your servlet into your web browser. That will call doGet(). To call doPost(), you'll have to write a little HTML page with a form with method="post" and action=the name of your servlet.
Robin