The init method is meant to init the servlet itself
Each statement executed causes a DB cursor to be created to execute the
operation
e.g. ReadCursor for executeQuery
e.g. UpdateCursor for executeUpdate
public class SurveyServlet extends HttpServlet {
private Connection connection;
private String fu;
private String bar;
private PreparedStatement updateVotes, totalVotes, results;
//if anything causing servletException inside this init methid would be thrown
your servlet will cause 503 or 500 or some exception which will throw
//ServletException
public void init( ServletConfig config ) throws ServletException
{
fu="fu";
bar="bar";
}
//Once init'ed I would wait for DoPost or DoGet or service methods for the
following sequence
protected void doPost( HttpServletRequest request,HttpServletResponse
response ) throws ServletException, IOException
{
// set up response to client
response.setContentType( "text/html" );
PrintWriter out = response.getWriter();
DecimalFormat twoDigits = new DecimalFormat( "0.00" );
// start XHTML document
out.println( "<?xml version = \"1.0\"?>" );
out.println( "<!DOCTYPE html PUBLIC \"-//W3C//DTD " +
"XHTML 1.0 Strict//EN\" \"http://www.w3.org"; +
"/TR/xhtml1/DTD/xhtml1-strict.dtd\">" );
out.println( "<html xmlns = \"http://www.w3.org/1999/xhtml\";>" );
// head section of document
out.println( "<head>" );
try
{ //load the Driver
Class.forName( "COM.cloudscape.core.RmiJdbcDriver" );
//acquire a Connection from the DriverManager
connection = DriverManager.getConnection(
"jdbc:rmi:jdbc:cloudscape:animalsurvey" );
// PreparedStatement to add one to vote total for a
// specific animal
updateVotes =
connection.prepareStatement(
"UPDATE surveyresults SET votes = votes + 1 " +
"WHERE id = ?"
);
updateVotes.setInt(1,value);
ResultSet rs = pst.executeUpdate();
// for any exception throw an UnavailableException to
// indicate that the servlet is not currently available
} //end try
catch ( Exception exception )
{
debug.log(exception.getMessage());
exception.printStackTrace();
throw new UnavailableException( exception.getMessage() );
}
//Any more SQL Statements should go here with the
connection/statement/execute/GetResults
} //doPost
YMMV
Martin--
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----- Original Message -----
From: "Mr. Steve Burrus" <[EMAIL PROTECTED]>
To: <users@tomcat.apache.org>
Sent: Sunday, January 28, 2007 4:48 PM
Subject: Need Help w. Database Servlet.
> hi all. I find myself in need of help/assistance with a longtime problem
> of mine and that is how do you get a servlet working with a backend
> database server?? Here is the basic SurveyServlet.java servlet and
> please notice that the database server in question is IBM's Cloudscape .
> after the servlet I have the html file which the servlet is supposed to
> work with. thanx in advance for anyone's help.
>
>
> import java.io.*;
> import java.text.*;
> import java.sql.*;
> import javax.servlet.*;
> import javax.servlet.http.*;
>
> public class SurveyServlet extends HttpServlet {
> private Connection connection;
> private PreparedStatement updateVotes, totalVotes, results;
>
> // set up database connection and prepare SQL statements
> public void init( ServletConfig config )
> throws ServletException
> {
> // attempt database connection and create PreparedStatements
> try {
> Class.forName( "COM.cloudscape.core.RmiJdbcDriver" );
> connection = DriverManager.getConnection(
> "jdbc:rmi:jdbc:cloudscape:animalsurvey" );
>
> // PreparedStatement to add one to vote total for a
> // specific animal
> updateVotes =
> connection.prepareStatement(
> "UPDATE surveyresults SET votes = votes + 1 " +
> "WHERE id = ?"
> );
>
> // PreparedStatement to sum the votes
> totalVotes =
> connection.prepareStatement(
> "SELECT sum( votes ) FROM surveyresults"
> );
>
> // PreparedStatement to obtain surveyoption table's data
> results =
> connection.prepareStatement(
> "SELECT surveyoption, votes, id " +
> "FROM surveyresults ORDER BY id"
> );
> }
>
> // for any exception throw an UnavailableException to
> // indicate that the servlet is not currently available
> catch ( Exception exception ) {
> exception.printStackTrace();
> throw new UnavailableException( exception.getMessage() );
> }
>
> } // end of init method
>
> // process survey response
> protected void doPost( HttpServletRequest request,
> HttpServletResponse response )
> throws ServletException, IOException
> {
> // set up response to client
> response.setContentType( "text/html" );
> PrintWriter out = response.getWriter();
> DecimalFormat twoDigits = new DecimalFormat( "0.00" );
>
> // start XHTML document
> out.println( "<?xml version = \"1.0\"?>" );
>
> out.println( "<!DOCTYPE html PUBLIC \"-//W3C//DTD " +
> "XHTML 1.0 Strict//EN\" \"http://www.w3.org"; +
> "/TR/xhtml1/DTD/xhtml1-strict.dtd\">" );
>
> out.println(
> "<html xmlns = \"http://www.w3.org/1999/xhtml\";>" );
>
> // head section of document
> out.println( "<head>" );
>
> // read current survey response
> int value =
> Integer.parseInt( request.getParameter( "animal" ) );
>
> // attempt to process a vote and display current results
> try {
>
> // update total for current survey response
> updateVotes.setInt( 1, value );
> updateVotes.executeUpdate();
>
> // get total of all survey responses
> ResultSet totalRS = totalVotes.executeQuery();
> totalRS.next();
> int total = totalRS.getInt( 1 );
>
> // get results
> ResultSet resultsRS = results.executeQuery();
> out.println( "<title>Thank you!</title>" );
> out.println( "</head>" );
>
> out.println( "<body>" );
> out.println( "<p>Thank you for participating." );
> out.println( "<br />Results:</p><pre>" );
>
> // process results
> int votes;
>
> while ( resultsRS.next() ) {
> out.print( resultsRS.getString( 1 ) );
> out.print( ": " );
> votes = resultsRS.getInt( 2 );
> out.print( twoDigits.format(
> ( double ) votes / total * 100 ) );
> out.print( "% responses: " );
> out.println( votes );
> }
>
> resultsRS.close();
>
> out.print( "Total responses: " );
> out.print( total );
>
> // end XHTML document
> out.println( "</pre></body></html>" );
> out.close();
> }
>
> // if database exception occurs, return error page
> catch ( SQLException sqlException ) {
> sqlException.printStackTrace();
> out.println( "<title>Error</title>" );
> out.println( "</head>" );
> out.println( "<body><p>Database error occurred. " );
> out.println( "Try again later.</p></body></html>" );
> out.close();
> }
>
> } // end of doPost method
>
> // close SQL statements and database when servlet terminates
> public void destroy()
> {
> // attempt to close statements and database connection
> try {
> updateVotes.close();
> totalVotes.close();
> results.close();
> connection.close();
> }
>
> // handle database exceptions by returning error to client
> catch( SQLException sqlException ) {
> sqlException.printStackTrace();
> }
> } // end of destroy method
> }
>
> the html file :
>
> <?xml version = "1.0"?>
> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
> "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd";>
>
> <!-- Survey.html -->
>
> <html xmlns = "http://www.w3.org/1999/xhtml";>
> <head>
> <title>Survey</title>
> </head>
>
> <body>
> <form method = "post" action = "/animalsurvey">
>
> <p>What is your favorite pet?</p>
>
> <p>
> <input type = "radio" name = "animal"
> value = "1" />Dog<br />
> <input type = "radio" name = "animal"
> value = "2" />Cat<br />
> <input type = "radio" name = "animal"
> value = "3" />Bird<br />
> <input type = "radio" name = "animal"
> value = "4" />Snake<br />
> <input type = "radio" name = "animal"
> value = "5" checked = "checked" />None
> </p>
>
> <p><input type = "submit" value = "Submit" /></p>
>
> </form>
> </body>
> </html>
>
>
>
>
>
>
> ---------------------------------------------------------------------
> To start a new topic, e-mail: users@tomcat.apache.org
> To unsubscribe, e-mail: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
>
>
