Jdbc - Class.forName(...)

can anyone explain to me the exact mechanism of using this statement to load a driver? I thought the forName method was supposed to return a reference he name of the class of the Object supplied as a parameter. All of a sudden the DriverManager knows what driver to use???
Class.forName("some.driver.package");Thanks

All of a sudden the DriverManager knows
what driver to use???And following on from what whoisfred said...
The DM doesn't really "know" which driver to use, but by registering itself with the DM, the driver makes itself eligible to be used for a given connection. Driver has a method [url http://java.sun.com/j2se/1.4.2/docs/api/java/sql/Driver.html#acceptsURL(java.lang.String)]acceptsURLurl. Presumably the DM calls this method on each registered driver until it either finds one that returns true, or it runs out of drivers (in which case it throws and exception with the message "No suitable driver found.")
You can look at the source for DriverManager if you want to confirm my assumption.

Similar Messages

JDBC:Class.forName() Vs registerDriver()

can anyone tell me the difference between Class.forName() and registerDriver()?

Genarlly the former calls the latter.
JDBC drivers have a static intialiser which calls DriverManager.registerDriver() on themselves.
Since there's no way to call registerDriver on a class without loading the class (and therefore, normally, having already had it call registerDriver) there's almost never a need to call it yourself.

Use of Class.forName() in JDBC

Hi,
I know that in JDBC "Class.forName()" is used to load the JDBC driver classes.
Is this the only purpose of "Class.forName()" method specially in JDBC?

thanks much..
ok so. calling the Class.forName automatically
creates an instance of a driver and registers it with
the DriverManager.more or less
When we use the string / string buffer class we don�t
need to explicitly load the classes exist in
�java.Lang� package.they get loaded - as do all classes - when your code first tries to use them.
But to get the JDBC connection, we need to insert the
code
�Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");�..
please clear my confusion.it's really because the JDBC driver might not be known at compile-time. Class.forName allows us to load classes at runtime we didn't know about at compile-time. you could just as easily load java.lang.String using the above method, but since the method takes a string, the class will be loaded already! you could also just as easily do
import sun.jdbc.odbc.JdbcOdbcDriver;
new JdbcOdbcDriver();that would also load the class. but that then couples your code to that particular driver. generally, in real applications, the driver classname would come from a config file, rather than hard-coded in the application. Class.forName() gives us that flexibility

Error in Class.forName("com.mysql.jdbc.driver")

Hi forum,
Please help me to solve the issue.
im using the following jsp code for genrating the reports using JASPER REPORTS
the JSP FILE
<%@ page contentType="text/html;charset=windows-1252"%>
<%@ page import="java.io.*"%>
<%@ page import="java.util.*"%>
<%@ page import="java.sql.*"%>
<%@ page import="javax.sql.DataSource"%>
<%@ page import="javax.naming.InitialContext"%>
<%@ page import="net.sf.jasperreports.engine.*"%>
<%@ page import="net.sf.jasperreports.engine.design.JasperDesign"%>
<%@ page import="net.sf.jasperreports.engine.xml.JRXmlLoader"%>
<%@ page import="net.sf.jasperreports.engine.export.*" %>
<%@ page import ="net.sf.jasperreports.engine.*"%>
<%@ page import ="net.sf.jasperreports.engine.JasperFillManager"%>
<%@ page import ="net.sf.jasperreports.engine.JRException"%>
<%@ page import="net.sf.jasperreports.engine.JasperReport"%>
<%@ page import="net.sf.jasperreports.engine.JasperPrint"%>
<html>
<body bgcolor="00ffcc">
<%
try{
Connection con = null;
String url="jdbc:mysql://localhost/customer";
String username = "root";
String password = "cmsadmin";
InputStream input=new FileInputStream(new File("C:/Documents and Settings/user/My Documents/NetBeansProjects/jasperreports/web/helloworld.xml"));
JasperDesign design = JRXmlLoader.load(input);
JasperReport report = JasperCompileManager.compileReport(design);
Map params = new HashMap();
params.put("reportTitle", "helloworld");
params.put("author", "Muthu Kumar");
params.put("startDate", (new java.util.Date()).toString());
params.put("ReportTitle", "PDF JasperReport");
<img class="emoticon" src="images/emoticons/confused.gif" border="0" alt="" />Class.forName("com.mysql.jdbc.Driver");<img class="emoticon" src="images/emoticons/confused.gif" border="0" alt="" /><img src="images/emoticons/confused.gif" border="0" alt="" />
con = DriverManager.getConnection(url,username,password);
JasperPrint print = JasperFillManager.fillReport(report, params, con);
OutputStream output=new FileOutputStream(new File("C:/Documents and Settings/user/My Documents/NetBeansProjects/jasperreports/helloreportworld.pdf"));
JasperExportManager.exportReportToPdfStream(print, output);
// JasperViewer.viewReport(print);
catch(SQLException es) {
out.println(es);
catch(JRException ex){
//ex.printStackTrace();
out.println(ex);
%>
</body>
</html>The error it is saying is in the line Class.forName(....) ;
Please look for the emoctions with question mark
i DOn know what to do.
Please help
Im comparin the below JRXML file as with the above code
<?xml version="1.0"?>
<!DOCTYPE jasperReport
PUBLIC "-//JasperReports//DTD Report Design//EN"
"http://jasperreports.sourceforge.net/dtds/jasperreport.dtd">
<jasperReport name="helloworld">
<parameter name="reportTitle" class="java.lang.String"/>
<parameter name="author" class="java.lang.String"/>
<parameter name="startDate" class="java.lang.String"/>
<queryString>
<![CDATA[SELECT * FROM customer order by UserID ]]>
</queryString>
<field name="UserID" class="java.lang.String"/>
<field name="UserName" class="java.lang.String"/>
<field name="City" class="java.lang.String"/>
<field name="State" class="java.lang.String"/>
<title>
<band height="60">
<textField>
<reportElement x="0" y="10" width="500" height="40"/>
<textElement textAlignment="Center">
<font size="24"/>
</textElement>
<textFieldExpression class="java.lang.String">
<![CDATA[$P{reportTitle}]]>
</textFieldExpression>
</textField>
<textField>
<reportElement x="0" y="40" width="500" height="20"/>
<textElement textAlignment="Center"/>
<textFieldExpression class="java.lang.String">
<![CDATA["Run by: " + $P{author}
+ " on " + $P{startDate}]]>
</textFieldExpression>
</textField>
</band>
</title>
<columnHeader>
<band height="30">
<rectangle>
<reportElement x="0" y="0" width="500" height="25"/>
<graphicElement/>
</rectangle>
<staticText>
<reportElement x="5" y="5" width="50" height="15"/>
<textElement/>
<text><![CDATA[UserID]]></text>
</staticText>
<staticText>
<reportElement x="55" y="5" width="150" height="15"/>
<text><![CDATA[UserName]]></text>
</staticText>
<staticText>
<reportElement x="205" y="5" width="255" height="15"/>
<text><![CDATA[City, State]]></text>
</staticText>
</band>
</columnHeader>
<detail>
<band height="20">
<textField>
<reportElement x="5" y="0" width="50" height="15"/>
<textElement/>
<textFieldExpression class="java.lang.String">
<![CDATA[$F{UserID}]]>
</textFieldExpression>
</textField>
<textField>
<reportElement x="55" y="0" width="150" height="15"/>
<textElement/>
<textFieldExpression class="java.lang.String">
<![CDATA[$F{UserName}]]>
</textFieldExpression>
</textField>
<textField>
<reportElement x="205" y="0" width="255" height="15"/>
<textElement/>
<textFieldExpression class="java.lang.String">
<![CDATA[$F{City} + ", " + $F{State}]]>
</textFieldExpression>
</textField>
</band>
</detail>
</jasperReport>

Glass_Fish wrote:
I have set the classpath in the environment variables in the my computer properties.The web container has it's own properties. The "system" classpath means absolutely nothing to it. Read your server's documentation.

Strange use of Class.forName() in JDBC

The following is the classical code to retreive data from a database via JDBC
        Connection con;
        Statement stmt;
        String querystring;
        String parametervalue = "";
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch(java.lang.ClassNotFoundException e) {
            System.err.print("ClassNotFoundException: ");
            System.err.println(e.getMessage());
        try {
            con = DriverManager.getConnection(dburl);
            stmt = con.createStatement();
            querystring = "select ParameterValue from Profile ";
            ResultSet rs = stmt.executeQuery(querystring);
            if(rs.next()) parametervalue = rs.getString("ParameterValue");
            rs.close();
            stmt.close();
            con.close();
        } catch(SQLException ex) {
            System.err.println("-----SQLException-----");
            System.err.println("SQLState: " + ex.getSQLState());
            System.err.println("Message: " + ex.getMessage());
            System.err.println("Vendor: " + ex.getErrorCode());
        return parametervalue;         but the use of Class.forName("com.mysql.jdbc.Driver") is strange. it doesn't need to get the returned Class
like: Class t = Class.forName("com.mysql.jdbc.Driver"),and the DriverManager knows which driver to use!
Any one can give an explanation?
thanks

* It's more natural from an OO perspective for me to
tell the manager about the classes it manages thanfor
the classes to know about the manager and tell it
about themselves.
No.Hmmm. Care to elaborate? I don't have anything to really back this up, but it seems to me that a class shouldn't have to know too much about the context in which it is used. Drivers shouldn't have to know that there is a DriverManager that will be managing them. IMHO.
I thought of another reason: Since you're doing either the Class.forName or the DriverManger.register in the client, no work is saved there either way (as you said, register is just as easy to call as forName), but using Class.forName adds extra complexity in the Drivers. I guess this is probably the same as, or very close to "protected users from themselves" though.
If the forName() doesn't happen somewhere then the
class doesn't get loaded.I'm thinking more along the lines of classes getting loaded in a different area of the code than the DB client. Some kind of plugin-type thing maybe, where the plugin manager automatically loads all the classes in a certain classpath-like set of diretories and jars, without knowing or caring what each one is (DB plugin, graphics plugin, encryption plugin, messaging plugin, etc.) or how it's used. The DB client then wouldn't know which specific driver(s) it has available, only that whatever was visible to the plugin manager will be loaded, and some subset of that could be DB drivers.
In this situation, it's not appropriate for the plugin manager to register the drivers, since it doesn't know anything about JDBC, and it's not appropriate for the DB client to register them, since it doesn't know what classes the plugin manager loaded.
I suppose the DB client could query the plugin manager for all its loaded plugins, then check if each one implements Driver, and if it does, then register it. Or maybe the plugin manager could even store a map whose keys are interface Class objects or interface names and whose values are lists of the plugins that implement that interface.
I don't know if this scenario is used, or is even good design, but it doesn't seem too farfetched. This is the kind of situation where it seems to me the driver is the one in the best position to know both a) he has been loaded and b) he needs to be registered.

Help! JSP w/ struts can't find Class.forName("com.mysql.jdbc.Driver")

I think this is just a directory structure issue but I can't figure it out. I am writing a JSP / Struts / MYSQL web application which uses the mysql JDBC connector. The connector (mysql-connector-java-5.1.6-bin.jar) is in the referenced libraries. If I write the line of code:
Class.forName("com.mysql.jdbc.Driver");
To load up the driver, it works in JSP files in the folder /projectname/webroot/web-inf just fine and I can go on to execute MySQL queries. However, I need to load up the driver in an action (.java action) with the directory structure /projectname/src/action and it throws the exception "class not found", I believe, it can no longer seem to get to the driver. Can anyone tell me how to resolve this problem?
Thanks in advance, I hope this is the correct place (I have done my best to find the right one).
Edited by: Arkanin on Apr 24, 2008 4:39 PM

Arkanin wrote:
I think this is just a directory structure issue but I can't figure it out. I am writing a JSP / Struts / MYSQL web application which uses the mysql JDBC connector. The connector (mysql-connector-java-5.1.6-bin.jar) is in the referenced libraries. Nope, it's not. I don't know what "referenced libraries" means. It has to be in CLASSPATH, and that isn't an environment variable.
If I write the line of code:
Class.forName("com.mysql.jdbc.Driver"); No, wrong.
The JAR file for the Driver class might go in the WEB-INF/lib of your web app. If you're using Tomcat 5.5.26, put it in common/lib.
%

Error class not found with Class.forName("oracle.jdbc.driver.OracleDriver")

sorry Got the solution...!!!!
Hi
I am trying to connect to oracle database on the server, oracle client installed on working m/c, I have placed classes111.zip (from oracle 8) in jdk1.1.8demojrelibext folder and I have set the classpath to the ext folder. The code
try
Class.forName("oracle.jdbc.driver.OracleDriver");
catch(Exception e)
when I run this code , error as
[[ java.lang.ClassNotFoundException: oracle.jdbc.driver.OracleDriver ]]
Please reply what are settings I should to to load this oracle driver,
Thanks
Mayank
Message was edited by:
user560333

I currently have this same problem. How did you solve yours see my post Cant find suitable driver.

Problems with Class.forName("com.sun.sql.jdbc.db2.DB2Driver")

In sun java studio enterprise 8
I'm able to connect to my local DB2 sample database by creating a database schema.
But when I try to execute a java class (main) using
Class.forName("com.sun.sql.jdbc.db2.DB2Driver"). It returns a not found condition.
what am I doing wrong? do I have to point the classpath to some directory?

try to add jar containing driver to
Your project -> Properties -> Libraries -> Run list.

Calling Class.forname("Jdbc Driver") twice..

Hi Frnds,
Wat will happen if if call
Class.forname("Jdbc Driver"); wat will happen..
Which class will be loaded into the JVM...
Cheers,
Sandeep K

You'll get an exception. "Jdbc Driver" isn't a valid "fully qualified classname".
Calling Class.forname a second time on the same FQN won't have any effect (except to return a pointer to the already loaded class).

Need help w corba/jdbc class

hi
i'm trying to get this class to work right, i don't think i'm coding it the right way, especially the getAllAccounts() and selectAccounts() methods. this code compiles cleanly, but i get runtime exceptions when i try to run my app. my runtime exceptions look like
############################ StackTrace ############################
java.lang.NullPointerException
at com.kafein.accountServices.AccountServiceImpl.getAllAccounts(AccountS
erviceImpl.java:218)
at com.kafein.idl.accountServices.AccountServicePOA._invoke(AccountServi
cePOA.java:74)
at org.jacorb.poa.RequestProcessor.invokeOperation(RequestProcessor.java
:247)
at org.jacorb.poa.RequestProcessor.process(RequestProcessor.java:477)
at org.jacorb.poa.RequestProcessor.run(RequestProcessor.java:604)
and
Creating 100 Accounts
org.omg.CORBA.UNKNOWN: This exception was reported by the server, it is only re-
thrown here. vmcid: 0x0 minor code: 0 completed: No
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Sou
rce)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at org.jacorb.orb.SystemExceptionHelper.read(SystemExceptionHelper.java:
157)
at org.jacorb.orb.connection.ReplyInputStream.checkExceptions(ReplyInput
Stream.java:117)
at org.jacorb.orb.Delegate.invoke(Delegate.java:942)
at org.omg.CORBA.portable.ObjectImpl._invoke(Unknown Source)
at com.kafein.idl.accountServices._AccountServiceStub.getAllAccounts(_Ac
countServiceStub.java:134)
at com.kafein.client.AccountClient.main(AccountClient.java:111)
org.omg.CORBA.UNKNOWN: This exception was reported by the server, it is only re-
thrown here. vmcid: 0x0 minor code: 0 completed: No
ORB shutting down...
code for this class is below...
// AccountServiceImpl.java: The AccountService Implementation
package com.kafein.accountServices;
import java.util.Hashtable;
import java.util.Calendar;
import java.util.GregorianCalendar;
import junit.framework.TestCase;
import junit.framework.Test;
import junit.framework.TestSuite;
import org.omg.PortableServer.*;
import com.kafein.idl.accountServices.AccountServicePOA;
import com.kafein.idl.accountServices.AccountEntryStruct;
import com.kafein.idl.accountServices.AccountStruct;
import com.kafein.idl.utilities.DateTimeStruct;
import com.kafein.idl.exceptions.NotFoundException;
import com.kafein.idl.exceptions.DataValidationException;
import com.kafein.idl.errorCodes.DataValidationErrorCodes;
import com.kafein.utils.ServiceHandler;
import com.kafein.utils.Log;
import java.net.URL;
import java.sql.*;
import java.util.*;
* AccountServiceImpl is an implementation of the
* idl.accountServices.AccountService interface.
public class AccountServiceImpl extends AccountServicePOA {
POA poa;
private Hashtable accounts = new Hashtable(); // collection of Accounts
private static int nextAccountID = 1; // global account ID
Connection connection;
Vector connections;
Statement statement;
PreparedStatement preparedStatement;
   * Construct an instance.
public AccountServiceImpl(POA aPOA, String driver, String url, String user, String password) {
    super();
    poa = aPOA;
    driver = driver;
    url = url;
    user = user;
    password = password;
    connections = new Vector();
    // Connect to Database
    try {
        connect(driver,url,user,password);
    catch(Exception e) {
           e.printStackTrace();
    // Simple Database Select
    try {
        testSimpleSelect();
    catch(Exception e) {
           e.printStackTrace();
    // Database Select
    try {
        testSelect();
    catch(Exception e) {
           e.printStackTrace();
   * Overloaded constructor for unit tests.
protected AccountServiceImpl() {
    poa = null;
   * createAccount is used by administrator to add a new Account
   * in the system.
   * @param newAccount AccountEntryStruct containing data for new account
   * @return int the new unique Account ID
   * @exception com.kafein.idl.exceptions.DataValidationException
public int createAccount(AccountEntryStruct newAccount) throws
    DataValidationException {
    validateData (newAccount); // throws DataValidationException;
    int accountID = getNextID();
    // Create new Account.
    Account anAccount = new Account(accountID,
                        newAccount.userName,
                        newAccount.userEmail,
                        newAccount.creditCardType,
                        newAccount.creditCardNumber,
                        newAccount.creditCardExpirationDate.year,
                        newAccount.creditCardExpirationDate.month,
                        newAccount.userPassword,
                        newAccount.initialBalance);
// Insert here / call method insertAccount() pass it in an account object
// or call manager object - accountmanager.put()
    // Insert Account into Database
    try {
        insertAccount(anAccount);
    catch(Exception e) {
           e.printStackTrace();
    accounts.put(accountID,anAccount);
    return accountID;
   * isAccountValid is used to validate a user logon.
   * @param accountID AccountID
   * @param userPassword String
   * @return boolean true to indicate an existing Account
public boolean isValidAccount (int accountID, String userPassword) {
    // Get account with key equal to accountID.
    AccountStruct anAccount;
    try {
      anAccount = (AccountStruct) getAccount (accountID);
    catch (NotFoundException e) {
      return false;
    // Verify password.
    return (anAccount.userPassword.equals(userPassword) ? true : false);
   * getAccount is used to retrieve an existing Account in the system
   * @param int AccountID
   * @return AccountStruct containing data for the existing Account
   * @exception com.kafein.idl.exceptions.NotFoundException
public AccountStruct getAccount(int accountID)throws
    NotFoundException {
    // Verify that accountID is within an appropriate interval.
    if (accountID < 1 || accountID > accounts.size()) {
      throw new NotFoundException(DataValidationErrorCodes.INVALID_ACCOUNT_ID,
                      "Account ID not found");
    // Get Account and convert to AccountStruct (which is returned).
    Account anAccount = (Account) accounts.get(accountID);
    return anAccount.getAccountStruct();
   * getAllAccounts is used to retrieve all existing Accounts in the system
   * @return AccountStruct[] containing all existing Accounts.
   * @fyi returns an empty sequence if no Accounts exist
// GetAllAcounts method v. 2 - rather than enumerating through the vector
// call a method that returns a collection of objs in that method where
// you do select stmts
public AccountStruct[] getAllAccounts() {
    // Allocate the array of AccountStructs.
    Vector results = new Vector();
    try {
            results = selectAccounts();
    catch(Exception e) {
           e.printStackTrace();
    //Vector results = selectAccounts();
    int lastKey = results.size();
    //int lastKey = accounts.size();
    AccountStruct[] accountSequence = new AccountStruct[lastKey];
    if (lastKey==0) {
      return accountSequence;
    // Create AccountStructs from Accounts.
    for (int i = 1; i <= lastKey; i++) {
      Account anAccount = (Account) accounts.get(i);
      accountSequence[i-1] = anAccount.getAccountStruct();
    return accountSequence;
   * validateData is used to check new account data.
   * @param newAccount AccountEntryStruct containing data for new account
   * @exception com.kafein.idl.exceptions.DataValidationException
protected void validateData(AccountEntryStruct newAccount) throws
    DataValidationException {
    // Check all of the member data in newAccount.
    if (newAccount.userName.equals("")) {
      throw new DataValidationException(
          DataValidationErrorCodes.INVALID_USER_NAME,
          "User Name must not be empty");
    if (newAccount.userEmail.equals("")) {
      throw new DataValidationException(
          DataValidationErrorCodes.INVALID_USER_EMAIL,
          "User Email must not be empty");
    if (newAccount.creditCardType.equals("")) {
      throw new DataValidationException(
          DataValidationErrorCodes.INVALID_CREDIT_CARD_TYPE,
          "Credit card type must not be empty");
    if (newAccount.creditCardNumber.equals("")) {
      throw new DataValidationException(
          DataValidationErrorCodes.INVALID_CREDIT_CARD_NUMBER,
          "Credit card number must not be empty");
    // Compare creditCardExpirationDate to current date
    // (we only consider year and month).
    GregorianCalendar now = new GregorianCalendar();
    DateTimeStruct proposed = newAccount.creditCardExpirationDate;
    if (proposed.year < now.get (Calendar.YEAR) ||
     (proposed.year == now.get (Calendar.YEAR) &&
      proposed.month < now.get (Calendar.MONTH) + 1)) {
      throw new DataValidationException(
          DataValidationErrorCodes.INVALID_CREDIT_CARD_EXPIRATION_DATE,
          "Credit card has expired");
    if (newAccount.userPassword.equals("")) {
      throw new DataValidationException(
          DataValidationErrorCodes.INVALID_USER_PASSWORD,
          "Password must not be empty");
    else if (!newAccount.userPassword.equals(newAccount.userPasswordVerification)) {
      throw new DataValidationException(
          DataValidationErrorCodes.INVALID_USER_PASSWORD,
          "Password verification failure");
    if (newAccount.initialBalance < 0.0F) {
      throw new DataValidationException(
          DataValidationErrorCodes.INVALID_BALANCE,
          "Account Balance cannot have a negative balance");
   * getNextID is used to generate a unique ID.
   * Needs a much better implementation that generates a globally unique ID!
   * @return int an Account ID
protected synchronized int getNextID() {
    nextAccountID++;
    return nextAccountID - 1;
   * override _default_POA to return this servant's POA, not Root POA
public POA _default_POA() {
    return poa;
   * jdbc related methods
public void connect(String driver, String url, String user, String password)
                throws Exception {
        try {
            // Load JDBC driver
            Class.forName(driver);
            System.out.println("Connecting to " + url);
            connection = DriverManager.getConnection(url, user, password);
            connections.add(connection);
            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 {
            Enumeration myEnum = connections.elements();
            while ( myEnum.hasMoreElements() ) {
                System.out.println("Closing connection");
                ((Connection) myEnum.nextElement()).close();
        } catch (Exception e) {
            System.err.println("System Exception in closeConnection");
            System.err.println(e);
            throw e;
private void testSimpleSelect() throws Exception {
        try {
            Statement statement = connection.createStatement();
            ResultSet rs = statement.executeQuery("Select 1 from ACCOUNT");
            if (rs != null && rs.next()) {
               int value = rs.getInt(1);
               System.out.println("Fetched value " + value);
            connection.commit();
            statement.close();
        } catch(Exception e) {
            System.err.println("System Exception in testSimpleSelect");
            System.err.println(e);
            throw e;
private void testSelect() throws Exception {
        try {
            Statement statement = connection.createStatement();
            ResultSet rs = statement.executeQuery(
                "Select ACCT_ID, ACCT_USERNAME, ACCT_USEREMAIL, ACCT_CC_TYPE, ACCT_CC_NUMBER, ACCT_CC_EXPYR, ACCT_CC_EXPMO, ACCT_USERPASSWORD, ACCT_USERBALANCE from ACCOUNT LIMIT 1");
            System.out.println("Account ID   User Name     User Email     CC Type     CC Number     CC Expyr CC Expmo User Password     User Balance");
            while (rs != null && rs.next()) {
                int acct_id = rs.getInt(1);
                String acct_username = rs.getString(2);
                String acct_useremail = rs.getString(3);
                String acct_cc_type = rs.getString(4);
                String acct_cc_number = rs.getString(5);
                int acct_cc_expyr = rs.getInt(6);
                int acct_cc_expmo = rs.getInt(7);
                String acct_userpassword = rs.getString(8);
                float acct_userbalance = rs.getFloat(9);
                System.out.println(acct_id + "         " +
                                   acct_username + "   " +
                                   acct_useremail + "   " +
                                   acct_cc_type + "   " +
                                   acct_cc_number + "   " +
                                   acct_cc_expyr + "   " +
                                   acct_cc_expmo + "   " +
                                   acct_userpassword + "   " +
                                   acct_userbalance);
            connection.commit();
            statement.close();
        } catch(Exception e) {
            System.err.println("System Exception in testSelect");
            System.err.println(e);
            throw e;
private void testLoadData() throws Exception {
        int numberOfAccounts = 5;
        String acct_username    = "<--20 BYTE STRING-->";
        String acct_useremail = "<--20 BYTE STRING-->";
     String acct_cc_type = "TEST ";
        String acct_cc_number = "<--20 BYTE STRING-->";
        int acct_cc_expyr = 2000;
        int acct_cc_expmo = 1;
        String acct_userpassword = "<--20 BYTE STRING-->";
        float     acct_userbalance = 0.0F;
        int     acct_id = 0;
     try {
            System.out.println("Inserting data...");
            connection.setAutoCommit(false);
            // Calculate Start time
            System.out.println("Starting data insertion (" + numberOfAccounts +
                " rows) into ACCOUNT table..");
            long startTime = System.currentTimeMillis();
            preparedStatement = connection.prepareStatement(
                "INSERT INTO ACCOUNT (ACCT_ID, ACCT_USERNAME, ACCT_USEREMAIL, ACCT_CC_TYPE, ACCT_CC_NUMBER, " +
                "ACCT_CC_EXPYR, ACCT_CC_EXPMO, ACCT_USERPASSWORD, ACCT_USERBALANCE) VALUES ( ?, ?, ?, ?, ?, ? , ?, ?, ?)");
            // Insert accounts in ACCOUNT table
            for (int i = 1; i <= numberOfAccounts; i++) {
                acct_id = i * 1000;
                preparedStatement.setInt(1, acct_id);
                preparedStatement.setString(2, acct_username);
                preparedStatement.setString(3, acct_useremail);
                preparedStatement.setString(4, acct_cc_type);
                preparedStatement.setString(5, acct_cc_number);
                preparedStatement.setInt(6, acct_cc_expyr);
                preparedStatement.setInt(7, acct_cc_expmo);
                preparedStatement.setString(8, acct_userpassword);
                preparedStatement.setFloat(9, acct_userbalance);
          preparedStatement.executeUpdate();
                connection.commit();
            System.out.println(numberOfAccounts + " accounts created.");
            preparedStatement.close();
            long stopTime = System.currentTimeMillis();
            System.out.println("Account table load complete.");
            System.out.println("Load time = " +
                               ((stopTime - startTime)/(1000f)) + " seconds");
            System.out.println("Data insertion complete");
        } catch(Exception e) {
            System.err.println("System Exception in loadData");
            System.err.println(e);
            throw e;
   * insertAccount is used to insert a new Account in the Database
   * @param int AccountID
   * @return AccountStruct containing data for the existing Account
private void insertAccount(Account anAccount) throws Exception {
          AccountStruct anAccountStruct = anAccount.getAccountStruct();
     int numberOfAccounts = 1;
     String acct_username    = anAccountStruct.userName;
        String acct_useremail = anAccountStruct.userEmail;
     String acct_cc_type = anAccountStruct.creditCardType;
        String acct_cc_number = anAccountStruct.creditCardNumber;
     int acct_cc_expyr = anAccountStruct.creditCardExpirationDate.year;
        int acct_cc_expmo = anAccountStruct.creditCardExpirationDate.month;
        String acct_userpassword = anAccountStruct.userPassword;
        float     acct_userbalance = anAccountStruct.accountBalance;
        int     acct_id = anAccountStruct.accountID;
     try {
            System.out.println("Inserting data...");
            connection.setAutoCommit(false);
//instead of system.out just log
            // Calculate Start time
            System.out.println("Starting data insertion ( 1" +
                " row) into ACCOUNT table..");
            long startTime = System.currentTimeMillis();
            preparedStatement = connection.prepareStatement(
                "INSERT INTO ACCOUNT (ACCT_ID, ACCT_USERNAME, ACCT_USEREMAIL, ACCT_CC_TYPE, ACCT_CC_NUMBER, " +
                "ACCT_CC_EXPYR, ACCT_CC_EXPMO, ACCT_USERPASSWORD, ACCT_USERBALANCE) VALUES ( ?, ?, ?, ?, ?, ? , ?, ?, ?)");
                acct_id = 1000;
                preparedStatement.setInt(1, acct_id);
                preparedStatement.setString(2, acct_username);
                preparedStatement.setString(3, acct_useremail);
                preparedStatement.setString(4, acct_cc_type);
                preparedStatement.setString(5, acct_cc_number);
                preparedStatement.setInt(6, acct_cc_expyr);
                preparedStatement.setInt(7, acct_cc_expmo);
                preparedStatement.setString(8, acct_userpassword);
                preparedStatement.setFloat(9, acct_userbalance);
          preparedStatement.executeUpdate();
                connection.commit();
            System.out.println("1 account created.");
            preparedStatement.close();
            long stopTime = System.currentTimeMillis();
            System.out.println("Account table load complete.");
            System.out.println("Load time = " +
                               ((stopTime - startTime)/(1000f)) + " seconds");
            System.out.println("Data insertion complete");
        } catch(Exception e) {
            System.err.println("System Exception in loadData");
            System.err.println(e);
            throw e;
private Vector selectAccounts() throws Exception {
        try {
            // Create Vector to hold individual Account values
         Vector mainvector = new Vector();
         Vector values = new Vector();
         Statement statement = connection.createStatement();
            ResultSet rs = statement.executeQuery(
                "Select ACCT_ID, ACCT_USERNAME, ACCT_USEREMAIL, ACCT_CC_TYPE, ACCT_CC_NUMBER, ACCT_CC_EXPYR, ACCT_CC_EXPMO, ACCT_USERPASSWORD, ACCT_USERBALANCE from ACCOUNT");
            System.out.println("Account ID   User Name     User Email     CC Type     CC Number     CC Expyr CC Expmo User Password     User Balance");
         // Iterate through result set
         while (rs != null && rs.next()) {
          // Make sure values is empty
          values.clear();
          int acct_id = rs.getInt(1);
                String acct_username = rs.getString(2);
                String acct_useremail = rs.getString(3);
                String acct_cc_type = rs.getString(4);
                String acct_cc_number = rs.getString(5);
                int acct_cc_expyr = rs.getInt(6);
                int acct_cc_expmo = rs.getInt(7);
                String acct_userpassword = rs.getString(8);
                float acct_userbalance = rs.getFloat(9);
          // Populate Vector values
          values.addElement(rs.getObject(1));
          values.addElement(rs.getObject(2));
          values.addElement(rs.getObject(3));
          values.addElement(rs.getObject(4));
          values.addElement(rs.getObject(5));
          values.addElement(rs.getObject(6));
          values.addElement(rs.getObject(7));
          values.addElement(rs.getObject(8));
          values.addElement(rs.getObject(9));
          mainvector.addElement(values);
                System.out.println(acct_id + "         " +
                                   acct_username + "   " +
                                   acct_useremail + "   " +
                                   acct_cc_type + "   " +
                                   acct_cc_number + "   " +
                                   acct_cc_expyr + "   " +
                                   acct_cc_expmo + "   " +
                                   acct_userpassword + "   " +
                                   acct_userbalance);
            connection.commit();
            statement.close();
         return mainvector;
        } catch(Exception e) {
            System.err.println("System Exception in selectAccounts");
            System.err.println(e);
            throw e;
    }

line 217 and 218 is
Account anAccount = (Account) accounts.get(i);
accountSequence[i-1] = anAccount.getAccountStruct();
i realized that
Account anAccount = (Account) accounts.get(i);
was a typo. what it should have been was
Account anAccount = (Account) results.get(i);
so my getAllAccounts() method now looks like
   * getAllAccounts is used to retrieve all existing Accounts in the system
   * @return AccountStruct[] containing all existing Accounts.
   * @fyi returns an empty sequence if no Accounts exist
// GetAllAcounts method v. 2 - rather than enumerating through the vector
// call a method that returns a collection of objs in that method where
// you do select stmts
public AccountStruct[] getAllAccounts() {
    // Allocate the array of AccountStructs.
    Vector results = new Vector();
    try {
            results = selectAccounts();
    catch(Exception e) {
           e.printStackTrace();
    //Vector results = selectAccounts();
    int lastKey = results.size();
    //int lastKey = accounts.size();
    AccountStruct[] accountSequence = new AccountStruct[lastKey];
    if (lastKey==0) {
      return accountSequence;
    // Create AccountStructs from Accounts.
    for (int i = 1; i <= lastKey; i++) {
      Account anAccount = (Account) results.get(i);
      accountSequence[i-1] = anAccount.however, i still get the same runtime errors.
is my selectAccounts() method returning a null?

Why class.forName to load driver

hi all,
as most of the times the loading of jdbc driver is carried out
by using the function class.forName, Why so ?
as i tryied with creating the object of the driver class like
Object driver = new <JDBC DRIVER>;and the code worked fine
so is there any difference in the two methods of loading the
drivers ?
if not wot is the use of method class.forname ?
thanx

That 's fine, but what if you change database back end in near future.
I will define a property and used class.forName ("read property").
In your case, you have to change the code about loading the JDBC driver as well.
Using std. JDBC API functionality and loading driver dynamically, leaves some of the part of the code that are not a candidate for a change in case back-end DB is changed.
BS

Difference between DriverManager.registerDriver and Class.forName?

Hi all,
I've noticed that the Oracle JDBC driver specifically asks to use DriverManager.registerDriver instead of Class.forName. What is the difference btw those 2 methods in loading and registering the driver?
Thanks.

I am trying to understand the jdbc, odbc drivers better.
Does the class my.sql.Driver refer to a driver for MySql or is it a driver itself?
with the lines one and two commented out, the code works fine. but with lines one and three commented out and the dbDriver being as specified in line two; no connection is made to the database. Can anyone explain this? and when i do Class.forName(dbDriver), is there a class by that name?
//String dbDriver = "sun.jdbc.odbc.JdbcOdbcDriver"; //one
//String dbDriver = "my.sql.Driver"; //two
String dbDriver = "MySql ODBC 3.51 Driver"; //three
String dbSource = "jdbc:odbc:mydb";
try {
     Class.forName(dbDriver);
     conn = DriverManager.getConnection(dbSource);
     statement = conn.createStatement();
} catch(Exception exception) {
     System.out.println(exception.getMessage()+" from the "+exception.toString());
     System.exit(1);

For class.forName()

Class.forName()
method is used in DataBase Connection
we cannot trap the returned value why n how it works in DataBase Connection

Class.forName()
method is used in DataBase Connection
we cannot trap the returned value why n how it works
in DataBase ConnectionYes, you can "trap" the returned value, but you don't need to. This call loads the driver class. For all JDBC drivers it is mandatory to have a static initializer that registers the driver at the DriverManager, so loading the class is all you need to do in order to make it known to JDBC.

Class.forName(driver) = ClassNotFoundException

hy all!
the following statements causes an error:
Class.forName("oracle.jdbc.driver.OracleDriver");I printed some informations about the exception:
Errorcause: null
Errormessage: oracle.jdbc.driver.OracleDriver
Class: class java.lang.ClassNotFoundException
StackTrace: [Ljava.lang.StackTraceElement;@16
(I�m using JDeveloper)
what do I have to do?? Is something missing on my harddrive??
can you guide me?
thanks!
lenaz

oracle jdeveloper build 10.1.2
1. select the project then right click
2. select the project properties
3. expand the Profiles and select the libraries
4. select the Oracle JDBC then click >
5. click ok

Why Class.forName?...

I'm trying to understand the use of Class.forName in JDBC programing. �What is the really goal for this class?
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
} catch(ClassNotFoundException ex){
// something
Regards.

I'm trying to understand the use of Class.forName in
JDBC programing. �What is the really goal for this
class?There are two implied questions...
-What does it do?
1. The class is loaded. All classes are loaded this way but normally the compiler does the work for you.
2. When a class is loaded, if there are any 'static initializers' in the class then those are run. Again true for any class when it is loaded.
3. JDBC drivers have a static initializer which registers the driver with the JDBC driver manager. See the DriverManager.registerDriver(Driver driver) method and the JDBC spec for more specific info.
-Why it is done this way?
As a guess because the original JDBC implementor(s) just found out about static initializers and thought they were 'cool'. It would be just as easy and more meaningful to do it using a different methodology.

Jdbc - Class.forName(...)

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