Hello all,
I've been trying to do a db connection thru JSP-bean(or servlet ?) but ran
into a problem and would appreciate if you could help to identify
the meaning of the error code.
There are 2 files that used to work:
numguess.jsp
NumberGuessBean.java.sav
Now I have a new code:
test_it.java
which connect to a database and do a very simple SQL:
String query = "select count(*) from TbAddress where City like '%Calgary%'";
I tested this code independently from another Java main program and it works.
But when I modified:
NumberGuessBean.java
to use an instance of "test_it" and run the numguess.jsp, I got an error code:
Error: 500
Unknown exception:
for which I don't know what causes it. Although it seems to occur in this very
line:
a_DSN = new test_it(); [in the reset() method, of
NumberGuessBean.java]
when I commented this line out, it works.
Thanks in advance for any help on this.
---Nam
numguess.jsp
=========
<!--
Number Guess Game
Written by Jason Hunter <[EMAIL PROTECTED]>, CTO, K&A Software
Copyright 1999, K&A Software, distributed by Sun with permission
-->
<%@ page import = "num.NumberGuessBean" %>
<jsp:useBean id="numguess" class="num.NumberGuessBean" scope="session"/>
<jsp:setProperty name="numguess" property="*"/>
<html>
<head><title>Number Guess</title></head>
<body bgcolor="white">
<font size=4>
<% if (numguess.getSuccess()) { %>
Congratulations! You got it.
And after just <%= numguess.getNumGuesses() %> tries.<p>
<% numguess.reset(); %>
Care to <a href="numguess.jsp">try again</a>?
<% } else if (numguess.getNumGuesses() == 0) { %>
Welcome to the Number Guess game.<p>
I'm thinking of a number between 1 and 100.<p>
<form method=get>
What's your guess? <input type=text name=guess>
<input type=submit value="Submit">
</form>
<% } else { %>
Good guess, but nope. Try <b><%= numguess.getHint() %></b>.
You have made <%= numguess.getNumGuesses() %> guesses.<p>
I'm thinking of a number between 1 and 100.<p>
<form method=get>
What's your guess? <input type=text name=guess>
<input type=submit value="Submit">
</form>
<% } %>
</font>
</body>
</html>
NumberGuessBean.java.sav
===================
// Number Guess Game
// Written by Jason Hunter <[EMAIL PROTECTED]>, CTO, K&A Software
// Copyright 1999, K&A Software, distributed by Sun with permission
package num;
import java.util.*;
public class NumberGuessBean {
int answer;
boolean success;
String hint;
int numGuesses;
public NumberGuessBean() {
reset();
}
public void setGuess(String guess) {
numGuesses++;
int g;
try {
g = Integer.parseInt(guess);
}
catch (NumberFormatException e) {
g = -1;
}
if (g == answer) {
success = true;
}
else if (g == -1) {
hint = "a number next time";
}
else if (g < answer) {
hint = "higher";
}
else if (g > answer) {
hint = "lower";
}
}
public boolean getSuccess() {
return success;
}
public String getHint() {
return "" + hint;
}
public int getNumGuesses() {
return numGuesses;
}
public void reset() {
answer = Math.abs(new Random().nextInt() % 100) + 1;
success = false;
numGuesses = 0;
}
}
NumberGuessBean.java
================
// Number Guess Game
// Written by Jason Hunter <[EMAIL PROTECTED]>, CTO, K&A Software
// Copyright 1999, K&A Software, distributed by Sun with permission
package num;
import java.util.*;
import test_it;
public class NumberGuessBean {
int answer;
boolean success;
String hint;
String sanswer;
int numGuesses;
test_it a_DSN;
public NumberGuessBean() {
reset();
}
public void setGuess(String guess) {
numGuesses++;
int g;
try {
g = Integer.parseInt(guess);
}
catch (NumberFormatException e) {
g = -1;
}
if (g == answer) {
success = true;
}
else if (g == -1) {
hint = "a number next time";
}
else if (g < answer) {
hint = "higher";
}
else if (g > answer) {
hint = "lower";
}
}
public boolean getSuccess() {
return success;
}
public String getHint() {
return "" + hint;
}
public int getNumGuesses() {
return numGuesses;
}
public void reset() {
a_DSN = new test_it();
answer = Math.abs(new Random().nextInt() % 100) + 1; // Commneted out for
now.
//sanswer = a_DSN.just_a_test();
//answer = Integer.parseInt(sanswer);
success = false;
numGuesses = 0;
}
}
test_it.java:
========
//----------------------------------------------------------------------------
//
// Module: test_it.java
//
// Description: Test class for ODBC API interface. This java application
// will connect to a JDBC driver, issue a select statement
// and display all result columns and rows
//
// USING: JDBC to ODBC Bridge
//
//----------------------------------------------------------------------------
import java.net.URL;
import java.sql.*;
public class test_it {
public String just_a_test () {
String url = "jdbc:odbc:wildrose";
String query = "select count(*) from TbAddress where City like
'%Calgary%'";
String ret = "-1";
try {
// Load the jdbc-odbc bridge driver
Class.forName ("sun.jdbc.odbc.JdbcOdbcDriver");
//
// This prints a lot of messages
//
// DriverManager.setLogStream(System.out);
// Attempt to connect to a driver. Each one
// of the registered drivers will be loaded until
// one is found that can process this URL
Connection con = DriverManager.getConnection (
url, "", "");
// If we were unable to connect, an exception
// would have been thrown. So, if we get here,
// we are successfully connected to the URL
// Check for, and display and warnings generated
// by the connect.
checkForWarning (con.getWarnings ());
// Get the DatabaseMetaData object and display
// some information about the connection
DatabaseMetaData dma = con.getMetaData ();
//System.out.println("\nConnected to " + dma.getURL());
dma.getURL();
//System.out.println("Driver " +
//dma.getDriverName());
dma.getDriverName();
//System.out.println("Version " +
//dma.getDriverVersion());
dma.getDriverVersion();
//System.out.println("");
// Create a Statement object so we can submit
// SQL statements to the driver
Statement stmt = con.createStatement ();
// Submit a query, creating a ResultSet object
ResultSet rs = stmt.executeQuery (query);
// Display all columns and rows from the result set
ret = dispResultSet (rs);
// Close the result set
rs.close();
// Close the statement
stmt.close();
// Close the connection
con.close();
}
catch (SQLException ex) {
// A SQLException was generated. Catch it and
// display the error information. Note that there
// could be multiple error objects chained
// together
//System.out.println ("\n*** SQLException caught ***\n");
while (ex != null) {
//System.out.println ("SQLState: " +
//ex.getSQLState ());
//System.out.println ("Message: " + ex.getMessage ());
//System.out.println ("Vendor: " +
//ex.getErrorCode ());
ex = ex.getNextException ();
//System.out.println ("");
}
}
catch (java.lang.Exception ex) {
// Got some other type of exception. Dump it.
//ex.printStackTrace ();
}
return(ret);
}
//-------------------------------------------------------------------
// checkForWarning
// Checks for and displays warnings. Returns true if a warning
// existed
//-------------------------------------------------------------------
private static boolean checkForWarning (SQLWarning warn)
throws SQLException {
boolean rc = false;
// If a SQLWarning object was given, display the
// warning messages. Note that there could be
// multiple warnings chained together
if (warn != null) {
//System.out.println ("\n *** Warning ***\n");
rc = true;
while (warn != null) {
//System.out.println ("SQLState: " +
//warn.getSQLState ());
//System.out.println ("Message: " +
//warn.getMessage ());
//System.out.println ("Vendor: " +
//warn.getErrorCode ());
//System.out.println ("");
warn = warn.getNextWarning ();
}
}
return rc;
}
//-------------------------------------------------------------------
// dispResultSet
// Displays all columns and rows in the given result set
//-------------------------------------------------------------------
private static String dispResultSet (ResultSet rs)
throws SQLException
{
int i;
String ret = "-2";
// Get the ResultSetMetaData. This will be used for
// the column headings
ResultSetMetaData rsmd = rs.getMetaData ();
// Get the number of columns in the result set
int numCols = rsmd.getColumnCount ();
// Display column headings
for (i=1; i<=numCols; i++) {
//if (i > 1) System.out.print(",");
//System.out.print(rsmd.getColumnLabel(i));
}
//System.out.println("");
// Display data, fetching until end of the result set
boolean more = rs.next ();
while (more) {
// Loop through each column, getting the
// column data and displaying
for (i = 1; i <= numCols; i++) {
//if (i > 1) System.out.print(",");
ret = rs.getString(i);
//System.out.print(ret);
//System.out.print(rs.getString(i));
}
//System.out.println("");
// Fetch the next result set row
more = rs.next ();
}
return(ret);
}
}
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