// my 3rd servlet, access to music dbe via jdbc

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


public class Music extends HttpServlet

  implements SingleThreadModel

{
  public String getServletInfo()
  {
    return "My 3rd Servlet, Lars Appel, Feb 1999";
  }


  static final String dbHref  = "jdbc:allbase://my.hp3000.here/musicdbe.grp.acct";
  static final String dbUser = "user.acct";
  static final String dbPass = "wont,tellyou";
  
  private Connection con;  // for JDBC access
  
  static private boolean missingDriver = false;  // for delayed Exception reporting

  private int requestCounter;  // to show servlet memory on web pages

  
  static
  {
    try 
    {
      Class.forName("com.hp.jdbc.allbase.JdbcDriver");
    } 
    catch (ClassNotFoundException e)
    {
      missingDriver = true;  // checked at init() time
    }
  }


  public void init(ServletConfig config) 
    throws ServletException
  {
    super.init( config );

    if (missingDriver)
      throw new UnavailableException( this, "missing jdbc:allbase driver" );
    else
      try
      {
        con = DriverManager.getConnection(dbHref,dbUser,dbPass);
      }
      catch (SQLException e)
      {
        throw new UnavailableException( this, e.toString() );
      };
  }

  
  public void doGet( HttpServletRequest req, HttpServletResponse res )
    throws IOException
  {
    res.setContentType( "text/html" );
    
    PrintWriter toClient = res.getWriter();
    
    String pathInfo = req.getPathInfo();

    if (pathInfo == null)
      showMainPage(toClient);
    else if (pathInfo.equals("/albums"))
      showAlbumList(toClient);
    else if (pathInfo.equals("/composers"))
      showComposerList(toClient);
    else
      showError(toClient);

    toClient.close();
  }


  private void showMainPage( PrintWriter out )
  {
    out.println(
      "<title>Music DBE via JDBC</title>\n" +
      "<h1>My JDBC Servlet Demo</h1>\n" +
      "<ul>\n" +
      "<li><a href=music/albums>Albums</a>\n" +
      "<li><a href=music/composers>Composers</a>\n" +
      "</ul>\n" +
      "<p>(request number " +
      ++requestCounter +
      ")</p>\n" +
      "<address>Lars Appel, February 1999</address>"
    );
  }


  private void showAlbumList( PrintWriter out )
  {
    out.println(
      "<title>Albums</title>\n" +
      "<h1>Albums in DBE</h1>\n" +
      "<tt><ul>\n"
    );

    try
    {
      Statement st = con.createStatement();

      String sql =
        "select albumcode,albumtitle,recordingco from music.albums;";

      ResultSet rs = st.executeQuery( sql );

      while ( rs.next() )
      {
        out.println(
          "<li>" + rs.getInt("albumcode") +
          " = " + rs.getString("albumtitle") +
          " , " + rs.getString("recordingco")
        );
      }
    }
    catch (SQLException e)
    {
      out.println(
        "<pre>SQL retrieval failed\n"
        + e.toString() +
        "\nContact web server admin</pre>"
      );
    }
    
    out.println(
      "</ul></tt>\n" +
      "<p>(request number " +
      ++requestCounter +
      ")</p>\n" +
      "<address>Lars Appel, February 1999</address>"
    );
  }


  private void showComposerList( PrintWriter out )
  {
    out.println(
      "<title>Composers</title>\n" +
      "<h1>Composers in DBE</h1>\n" +
      "<tt><ul>\n"
    );

    try
    {
      Statement st = con.createStatement();

      String sql =
        "select composername,birthplace,birth,death from music.composers;";

      ResultSet rs = st.executeQuery( sql );

      while ( rs.next() )
      {
        out.println(
          "<li>" + rs.getString("composername") +
          " , " + rs.getString("birthplace") +
          " , " + rs.getString("birth") +
          " - " + rs.getString("death")
        );
      }
    }
    catch (SQLException e)
    {
      out.println(
        "<pre>SQL retrieval failed\n"
        + e.toString() +
        "\nContact web server admin</pre>"
      );
    }
    
    out.println(
      "</ul></tt>\n" +
      "<p>(request number " +
      ++requestCounter +
      ")</p>\n" +
      "<address>Lars Appel, February 1999</address>"
    );
  }


  private void showError( PrintWriter out )
  {
    out.println(
      "<title>Error</title>\n" +
      "<h2>Something went wrong, hehehe ;-)</h2>"
    );
  }
}