Java Answers Forum - connection problem

Articles |
News |
Weblogs |
Books |
Forums

Artima Forums | Articles | Weblogs | Java Answers | News

Sponsored Link •

Java Answers Forum
connection problem

2 replies on 1 page. Most recent reply: Oct 19, 2004 7:40 PM by Yufeng Lu

Welcome Guest
Sign In

Back to Topic List

Reply to this Topic

Search Forum

Threaded View


Previous Topic		Next Topic

Flat View: This topic has 2 replies on 1 page

Yufeng Lu

Posts: 2
Nickname: beter
Registered: Oct, 2004

connection problem

Posted: Oct 18, 2004 8:52 PM

Hi there:

I have a java program which I want to use it to create table in MS SQL server database. The connection seems successful. But I got NullPointerException. I need help
about it. My program and the error is followed. Thank you so much for your help.

beter

// CreateTables.java

import java.net.URL;
import java.sql.*;
import java.util.*;

/**
* CreateTables is used to create a table used in the project
*
* @author Beter
* @since 10/15/2004
* @version 1.0
*/

public class CreateTables
{
Connection connection;
Statement statement;
PreparedStatement preparedStatement;

public static void main(String[] args) {
try {
CreateTables createTables = new CreateTables();
createTables.create(); /* line 24 */
}
catch (Exception e) {
e.printStackTrace();
}
}

public void create()
throws Exception {

connect();
createAccountTable(); /* line 35 */
closeConnection();
}

public void connect() throws Exception {

try {

// Load JDBC driver
DriverManager.registerDriver(new
com.microsoft.jdbc.sqlserver.SQLServerDriver());

System.out.println("Connecting to Billpayment...");

Connection connection = DriverManager.getConnection(
"jdbc:microsoft:sqlserver://TIGER:1433; DataBaseName=Billpayment;User=sa;Password=beter");
System.out.println("Connection successful");

// Meta data
DatabaseMetaData meta = connection.getMetaData();
System.out.println("\nDriver Information");
System.out.println("Driver Name: "
+ meta.getDriverName());
System.out.println("Driver Version: "
+ meta.getDriverVersion());
System.out.println("\nDatabase Information ");
System.out.println("Database Name: "
+ meta.getDatabaseProductName());
System.out.println("Database Version: "+
meta.getDatabaseProductVersion());

connection.setAutoCommit(false);
} catch(Exception e) {
System.err.println("System Exception in connect");
System.err.println(e);
throw e;
}
}

public void closeConnection() throws Exception {
try {
System.out.println("Closing connection");
connection.close();
}
catch (Exception e)
{
System.err.println("System Exception in closeConnection");
System.err.println(e);
throw e;
}
}

private void createAccountTable()
throws SQLException, Exception {

try {

System.out.println("Creating tables...");
Statement statement = connection.createStatement();/*line 94*/
statement.execute("CREATE TABLE ACCOUNT(" +
"ACCT_ID INT NOT NULL, " +
"NAME CHAR(30) NOT NULL, " +
"USER_PSWD CHAR(20) NOT NULL," +
"EMAIL CHAR(40) NOT NULL, " +
"PHONE_NO CHAR(30) NOT NULL, " +
"BALANCE REAL NOT NULL)");

connection.commit();
statement.close();
}
catch(Exception e) {
System.err.println("System Exception in createAccountTable");
System.err.println(e);
throw e;
}
}
}

C:\Project>javac CreateTables.java

C:\Project>java CreateTables
Connecting to Billpayment...
Connection successful

Driver Information
Driver Name: SQLServer
Driver Version: 2.2.0040

Database Information
Database Name: Microsoft SQL Server
Database Version: Microsoft SQL Server 2000
- 8.00.194 (Intel X86)
Aug 6 2000 00:57:48
Copyright (c) 1988-2000 Microsoft Corporation
Enterprise Evaluation Edition on Windows NT 5.1
(Build 2600: Service Pack 1)

Creating tables...
System Exception in createAccountTable
java.lang.NullPointerException
java.lang.NullPointerExceptio n
at CreateTables.createAccountTable(CreateTables.java:94)
at CreateTables.create(CreateTables.java:35)
at CreateTables.main(CreateTables.java:24)

Matthias Neumair

Posts: 660
Nickname: neumi
Registered: Sep, 2003

Re: connection problem

Posted: Oct 19, 2004 6:53 AM

Your error lies in the following line.

Connection connection = DriverManager.getConnection( ...

Try tu use
connection = DriverManager.getConnection( ...
instead.

Explanation:

class C {

Connection c;

public C () {
method1();
method2();
}

void method1 {
Connection c = createConnection();
//At this point you should assing c to this.c
}
void method2 {
c.doSomethingVeryImportant();
//this will result in a NullPointerException, because you never assinged c from method1 to this.c
}
}

Yufeng Lu

Posts: 2
Nickname: beter
Registered: Oct, 2004

Re: connection problem

Posted: Oct 19, 2004 7:40 PM

Thank you so much, neumi. It solved my problem. I realy appreciate it.

Beter

Flat View: This topic has 2 replies on 1 page

Previous Topic

Next Topic


	Web Artima.com