Please help... - Dev Shed

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March 28th, 2003, 12:12 AM

supersonic

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Join Date: Aug 2001

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Please help...

Please help... Everytime I access db.jsp I get the following error:

org.apache.jasper.JasperException: Exception: An unknown error occurred: java.lang.NullPointerException

Here's my javabean

package beans.bag;

import java.sql.*;
import java.util.*;

public class connectDB {

/* DECLARE VARIABLES */
String error;

String host = "localhost";
String user = "";
String pass = "";
// private String database;
Connection con;
// private ResultSet data;

// public connectDB() {}

public void connect(String database) throws ClassNotFoundException, SQLException, Exception {
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
String dbh = "jdbc:mysql://" + host + "/" + database + "?user=" + user + "&password=" + pass;
Connection con = DriverManager.getConnection(dbh);
}
catch (ClassNotFoundException cnfE) {
error = "ClassNotFoundException: Could not locate DB driver.";
throw new ClassNotFoundException (error);
}
catch (SQLException sqlE) {
error = "SQLException: Could not connect to " + database;
throw new SQLException (error);
}
catch (Exception eE) {
error = "Exception: An unknown error occured: " + eE;
}
}

public ResultSet returnResults() throws SQLException, Exception {
ResultSet rs;
try {
Statement sth = con.createStatement();
String query = "SELECT * FROM 01_Users";
rs = sth.executeQuery(query);
}
catch (SQLException sqlE) {
error = "Fcuuuuu" + sqlE;
throw new SQLException (error);
}
catch (Exception eE) {
error = "Exception: An unknown error occurred: " + eE;
throw new Exception (error);
}

return rs;
}
}

And here's my jsp page

<%@ page contentType="text/html; charset=iso-8859-1" language="java" import="java.sql.*, java.io.*, java.util.*" %>
<jsp:useBean id="dbc" scope="page" class="beans.bag.connectDB" />

<html>
<head>
<title>Database<title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>

<body>

<%
dbc.connect ("epower_e_power");
ResultSet rs = dbc.returnResults ();
while (rs.next()) {
// some stuff happens
}
%>

</body>
</html>

Can some one please help me...
Thanking you in advance

Frank

March 28th, 2003, 08:23 AM

Nemi

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Location: Lincoln, NE. USA

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Can you post the whole stack trace? It may say where the null pointer exception is happening at.

March 28th, 2003, 11:57 AM

ishnid

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I haven't used beans myself but I would imagine that your connectDB class needs a constructor. Your NullPointerException is possibly caused because you're not instantiating your connectDB class. Try this at the top of it:

Code:

/* DECLARE VARIABLES */
private String error;
private String host;
private String user;
private String pass;
private Connection con;

public connectDB() {
   host = "localhost";
   user = "blah";
   pass="blah";
}

I also see in your connect() method you have declared 'con' as a Connection object again. You've already done that when you're declaring variables at the top so you probably shouldn't do it again.

Of course, as I said, I haven't used beans before so I could be totally wrong

- still, no harm in trying eh?
~ishnid

__________________
~ishnid;

Have you tried:
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March 28th, 2003, 11:58 AM

bricker42

Moderator =(8^(|)

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Location: Sacramento, CA

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I don't know if this is the problem, but try changing

Code:

 Connection con = DriverManager.getConnection(dbh);

to be

Code:

con = DriverManager.getConnection(dbh);

Also, you should probably make your host/user/pass/con variables private, but that's a seperate issue

__________________
-james

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