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

Similar Messages

Why Class.forName("driver class") ?

Hi,
whay we are using Class.forName("driver class"). why we dont import the driver package and access the required classes and methods?
for eg:
insead of calling
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver"); ,can we use import com.microsoft.jdbc.sqlserver.*; ?
what is the use of DriverManager in this context? any connection between DriverManager and Class.forName() ?
expecting answers.

sure you can import the packages and use the classes directly but that defeats the whole purpose of pluggable drivers.
Class.forName causes the class to be loaded and as stated before that should cause the driver to register itself with the driver manager.
so then if you have a system where you are talking to several different database vendors then you don't have to worry about which is which as the DriverManager handles it for you.
the big pros that i have actually seen though for having this be pluggable and not hard-coded (with the exception of the URL although you can do this dynamically as well) is what happens if you switch databases. if you import the package and use fully named classes and you switch databases at some point (could be just an upgrade of the same vendor's database) you are screwed.
same problem could happen if you switch drivers for some reason.
at any rate if you use things properly and are careful then you should only ever have to change your URL the rest of the code is fine if you use the DriverManager and use the drivers dynamically otherwise...

What is Class.forName

We are using Class.forName("driver class") statement for registering the driver class. But after writing this statement we are not using any refernce to that Class.forName, why it is needed actually.

It causes the class to get loaded. That in turn causes the static initializer to run. Which registers it as an available driver, allowing you to use it from within JDBC.

Need Help Loading Sqlbase Driver Using Class.forName(...

I'm having trouble connecting to a Sqlbase database on my PC. The problem seems to be with loading the driver with the "Class.forName" method. My source code (listed below) is in the "C:\My Documents\java" folder. I installed the Sqlbase driver in "C:\com\centurasoft\java\sqlbase" folder. The driver installation modified my autoexec.bat file to include the line "SET CLASSPATH=C:\com\centurasoft\java\sqlbase".
The epdmo database is in a folder on my D:\ drive.
It seems to find the SqlbaseDriver.class file, but for some reason it can't load it. I would greatly appreciate any suggestions as to how I can fix this.
With the line -- Class.forName("centura.java.sqlbase.SqlbaseDriver");
The SqlbaseEx.java program will compile, but I get the following error
when I try to run it:
Exception in thread "main" java.lang.NoClassDefFoundError: SqlbaseDriver (wrong name: com/centurasoft/java/sqlbase/SqlbaseDriver)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
... [several more lines like these]
at SqlbaseEx.main(SqlbaseEx.java:25)
With the line -- DriverManager.registerDriver(new SqlbaseDriver());
The SqlbaseEx.java program will NOT compile. I get the following error:
SqlbaseEx.java:21: cannot access SqlbaseDriver
bad class file: C:\com\centurasoft\java\sqlbase\SqlbaseDriver.class
class file contains wrong class: com.centurasoft.java.sqlbase.SqlbaseDriver
Please remove or make sure it appears in the correct subdirectory of the classpath.
Also, does the line -- String url = "jdbc:sqlbase:epdmo";
look OK? I've seen numerous examples and they all have some values separated by slashes //. Am I
missing something here that will bite me when I get past this driver loading error?
import java.sql.*;
// Create the ...
public class SqlbaseEx {
public static void main(String args[]) {
String url = "jdbc:sqlbase:epdmo";
Connection con;
String createString;
createString = "create table COFFEES " +
"(COF_NAME varchar(32), " +
"SUP_ID int, " +
"PRICE float, " +
"SALES int, " +
"TOTAL int)";
Statement stmt;
try {
Class.forName("centura.java.sqlbase.SqlbaseDriver");
// DriverManager.registerDriver(new SqlbaseDriver());
} catch(java.lang.ClassNotFoundException e) {
System.err.print("ClassNotFoundException: ");
System.err.println(e.getMessage());
try {
con = DriverManager.getConnection(url, "SYSADM", "SYSADM");
stmt = con.createStatement();
stmt.executeUpdate(createString);
stmt.close();
con.close();
} catch(SQLException ex) {
System.err.println("SQLException: " + ex.getMessage());

Thanks for the reply.
Upon further testing, I think my original post was slightly incorrect: if I use either of the following lines --
Class.forName("com.centurasoft.java.sqlbase.SqlbaseDriver");
or
Class.forName("centura.java.sqlbase.SqlbaseDriver");
I get the following error at runtime:
ClassNotFoundException: com.centurasoft.java.sqlbase.SqlbaseDriver
or
ClassNotFoundException: centura.java.sqlbase.SqlbaseDriver
It is when I use the line -- Class.forName("SqlbaseDriver");
that I get the long error message in my original post.
I don't understand why it can't find/load the driver. I feel like I've covered all the bases -- I've tried numerous variations of the driver name in the Class.forName method, my classpath variable seems to be set correctly. Does it matter what folder I compile my program in? Right now, I've just been compiling it in the same folder as the driver file -- c:\com\centurasoft\java\sqlbase.

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.

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.

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

ClassNotFoundException when using Class.forName(), thx

in a study app, i try to use Class.forName() to load any class then get its properties (fields, methods etc. vs reflect).
the (Frame based) app is in directory:
c:\app\StudyApp.class
there is a "Open class" button on the app, click the button, i use FileChooser to open any class file.
i.e. open a class (assume it is not packaged)
d:\dir\TheClass.class
coding in StudyApp.java is:
Class cls=Class.forName("TheClass");
now a ClassNotFoundException throws when call Class.forName() above.
it is easy to understand why throw the exception because i never tell where the class is. it is in directory
d:\dir
my question is: how to tell VM the directory.
the directory d:\dir can not be applied to -classpath when run java.exe StudyApp, because the directory is random one at run-time.
i tried to change System property (i.e. "java.class.path", 'user.dir" etc. none of them can fix the problem.
thanks in advance for any help

This probably does a lot more than you need:
import java.util.*;
import java.io.*;
import java.util.jar.*;
import java.lang.*;
public class ClassFileFinder extends ClassLoader
     List cpath = new LinkedList();
     void addFile(File f) {
          if(f.isDirectory() || (f.isFile() && f.canRead() &&
                                      f.getName().endsWith(".jar")))
               cpath.add(f);
     public byte[] classData(String className) {
          String cname = className.replace('.', File.separatorChar) + ".class";
          Iterator it = cpath.iterator();
          while(it.hasNext()) {
               File f = (File)it.next();
               try {
                    if(f.isDirectory()) {
                         File cFile = new File(f, cname);
                         if(cFile.isFile()) {
                              byte[] buf = new byte[(int)cFile.length()];
                              InputStream in = new FileInputStream(cFile);
                              int off = 0, l;
                              while((l = in.read(buf, off, buf.length - off)) > 0) {
                                   off += l;
                                   if(off >= buf.length) break;
                              in.read(buf);
                              in.close();
                              return buf;
                    } else if (f.isFile()) {
                         JarFile jar = new JarFile(f);
                         JarEntry ent = jar.getJarEntry(cname);
                         if(ent != null) {
                              byte[] buf = new byte[(int)ent.getSize()];
                              int off = 0, l;
                              InputStream in = jar.getInputStream(ent);
                              while((l = in.read(buf, off, buf.length - off)) > 0) {
                                   off += l;
                                   if(off >= buf.length) break;
                              in.close();
                              return buf;
               } catch (IOException e) {
          return null;
     public Class findClass(String className) throws ClassNotFoundException{
          byte[] data = classData(className);
          if(data == null)
               return getParent().loadClass(className);
          else
               return defineClass(className,data,0, data.length);
}Create an instance, Add directories and/or jar files with addFile then loadClass the class you want.

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.
%

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).

Why Class.forName is used to load the driver ?

Hi all,
Why Class.forName() is used to load the driver ?. Can I use any other method to load the driver safely ?.
rgds
Antony Paul

That's still redundant. Sure, it works. Here are some equivalent forms:
    new MySqlDriver();
    DriverManager.registerDriver(new MySqlDriver());
    New LinkedList().add(new MySqlDriver());
    if (new MySqlDriver() == new MySqlDriver())
        System.out.println("department of redundancy department");
    Driver unusedVariable[] = new Driver[] { new MySqlDriver() };
    Class anotherUnusedVariable = MySqlDriver.class; // I'm not 100% sure this works
    new File(new MySqlDriver().toString());
    while (new MySqlDriver() == null)
    new Double(Math.sqrt(new MySqlDriver().toString().length()) / 42);

How does Class.forName() get a driver registered with DriverManager

From the documentation, Class.forName() tends to loads the specified class via the class loader. But if we use it to load the class of a jdbc connection driver, how does it get automatically registered with DriverManager?
Neerav

yorkroad wrote:
No. Class.ForName("whatever") intializes the class. As for registering it with the DriverManager, this is from the API:
When the method getConnection is called, the DriverManager will attempt to locate a suitable driver from amongst those loaded at initialization and those loaded explicitly using the same classloader as the current applet or application.
You could use DriverManager.registerDriver (new oracle.jdbc.driver.OracleDriver()); which does it all in one. (Although keep in mind that will require an Oracle import in your code!)
m
Edited by: yorkroad on Nov 4, 2009 3:42 PMNo, loading the Class with Class.forName already registers the driver, as already said. Where DriverManager "searches" is among those registered classes. The method detailed above does not do anything more than simply calling Class.forName() with the added drawback that the Driver jarfile must be present at compile time, and, in order to change DBs you would have to change and recompile your code.

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.

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.

Servlet outputstream doesn't work after class.forname

hi there,
i'm beginner to servlets and jdbc i was trying a code
the servlet outputstream doesn't work after registerting the mysql driver
here is the code:
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class JDBCServo extends HttpServlet
     private Connection con;
     private Statement stmt;
     protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
          // TODO Auto-generated method stub
          try
               ServletOutputStream out = res.getOutputStream();
               out.println("WELCOME");
               Class.forName("com.mysql.jdbc.Driver");
               con = DriverManager.getConnection("jdbc:mysql://localhost/books" , "root" , null);
               stmt = con.createStatement();
               ResultSet result = stmt.executeQuery("select * from book");
               result.next();
               con.close();
               out.println(result.getObject(1)+" "+result.getObject(2));
               out.close();
          }catch(SQLException e){}
          catch(ClassNotFoundException e){e.printStackTrace();}
}

That would almost certainly be because you didn't put that class in the classpath, and therefore Class.forName() throws an exception.

Class.forName(driver) = ClassNotFoundException

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