ClassNotFoundException

[Jorge Cecílio]

Hi all

I'm having no "luck" trying my first-time connect to an I-SE server from a
Java application, using JDBC.
I'm always getting then error:
"Error: java.lang.ClassNotFoundException: com.informix.jdbc.IfxDriver"

I suspect the problem is in my CLASSPATH system variable, but I don't know
how to set it. Or, perhaps, the strings I'm using aren't correct.
Facts:
1) My network is "up and running";
2) Informix-SE is on a Unix remote machine;
3) My Java app is on Windows XP Home;
4) Informix Client-SDK 2.81 TC3 is installed on XP;
5) ODBC has no problems
(I've an MS-Access app that retrieves data from my SE server. My Java
app, with JDBC-ODBC bridge, also works fine);
6) Using Informix Client-SDK dbping, every connection are made successfully,
except... JDBC!;
7) In JDBC dbping tab, only "com.informix.jdbc.IfxDriver" seems to be the
right value since the other two options appears to be for db2
(COM.ibm.db2.jdbc.app.DB2Driver and COM.ibm.db2.jdbc.net.DB2Driver)
8) I'm trying protocol "jdbc:informix-sqli". The other option is "jdbc:db2"
(dbping);
9) My Java app:
try {
//Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); //jdbc-odbc
bridge: works fine!
Class.forName("com.informix.jdbc.IfxDriver");
} catch(java.lang.ClassNotFoundException e) {
System.err.print("ClassNotFoundException: ");
System.err.println(e.getMessage());
}

try {
//String url = "jdbc:odbc:ifx_dsn"; //jdbc-odbc bridge: works
fine!
String url = "jdbc:informix-sqli"
Connection con = DriverManager.getConnection(url, "login",
"password");
Statement stmt = con.createStatement();
//retrieval of values
(...)
}
stmt.close();
con.close();
} catch(SQLException ex) {
System.err.println("SQLException: " + ex.getMessage());
}

On JDBC dbping tab is written "This Utility assumes that you have a JDBC
driver installed and a CLASSPATH set before running DBPING"
a) What do they mean by having a JDBC driver installed? Isn't this driver
installed when I installed Informix-SDK? If not, how can I get it?
b) Do I have to do something like I did to the ODBC driver (by creating and
configuring a
DSN)? Where and how?
c) I know CLASSPATH system variable isn't set. Should I set it in my system?
By what value? By a path within Informix-SDK folders? Should CLASSPATH be
set anywhere else (e.g. setnet32)?
I suspect the problem is in my CLASSPATH system variable, but I don't know
how to set it. Or, perhaps, the strings I'm using aren't correct.
Can Anyone help?

Thanks in advance,
Jorge Cecilio

[Tjerk Wolterink]

[cut]

When you using database you must have the JDBC Driver for that type of database.
JDBC: Java Database Connectivity.
JDBC Defines an framework/api for java connecting to sql databases.
It has some Interface objets in iut that a specific driver for a specific database must implement.

So you must have a driver for your specific database in your classpath
The driver you want to use is: com.informix.jdbc.IfxDriver

On JDBC dbping tab is written "This Utility assumes that you have a JDBC
driver installed and a CLASSPATH set before running DBPING"
a) What do they mean by having a JDBC driver installed? Isn't this driver
installed when I installed Informix-SDK? If not, how can I get it?
I think, but am not sure, that the driver is in your Informix-SDK
But you must include the .jar or .class that is the driver in your classpath.
b) Do I have to do something like I did to the ODBC driver (by creating and
configuring a
DSN)? Where and how?
dsn? i do not follow you here.
c) I know CLASSPATH system variable isn't set. Should I set it in my system?
By what value? By a path within Informix-SDK folders? Should CLASSPATH be
set anywhere else (e.g. setnet32)?
When you run your application you must bee sure that the com.informix.jdbc.IfxDriver
class is in your classpath, see the documentation of Informix where com.informix.jdbc.IfxDriver resides.

I suspect the problem is in my CLASSPATH system variable, but I don't know
how to set it. Or, perhaps, the strings I'm using aren't correct.
Can Anyone help?
You CAN set your classpath system var to include com.informix.jdbc.IfxDriver but it will then only
work on your computer. Better is to set the classpath in your application,
for example if you start your application from a .jar you can include com.informix.jdbc.IfxDriver
by editing the manifest file of the jar.

Else you could create a Start script that sets up the classpath first

Thanks in advance,
Jorge Cecilio

[Stijn Verholen]

Jorge Cecílio wrote:

Hi all

I'm having no "luck" trying my first-time connect to an I-SE server from a
Java application, using JDBC.
I'm always getting then error:
"Error: java.lang.ClassNotFoundException: com.informix.jdbc.IfxDriver"

I suspect the problem is in my CLASSPATH system variable, but I don't know
how to set it. Or, perhaps, the strings I'm using aren't correct.
Facts:
1) My network is "up and running";
2) Informix-SE is on a Unix remote machine;
3) My Java app is on Windows XP Home;
4) Informix Client-SDK 2.81 TC3 is installed on XP;
5) ODBC has no problems
(I've an MS-Access app that retrieves data from my SE server. My Java
app, with JDBC-ODBC bridge, also works fine);
6) Using Informix Client-SDK dbping, every connection are made successfully,
except... JDBC!;
7) In JDBC dbping tab, only "com.informix.jdbc.IfxDriver" seems to be the
right value since the other two options appears to be for db2
(COM.ibm.db2.jdbc.app.DB2Driver and COM.ibm.db2.jdbc.net.DB2Driver)
8) I'm trying protocol "jdbc:informix-sqli". The other option is "jdbc:db2"
(dbping);
9) My Java app:
try {
//Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); //jdbc-odbc
bridge: works fine!
Class.forName("com.informix.jdbc.IfxDriver");
} catch(java.lang.ClassNotFoundException e) {
System.err.print("ClassNotFoundException: ");
System.err.println(e.getMessage());
}

try {
//String url = "jdbc:odbc:ifx_dsn"; //jdbc-odbc bridge: works
fine!
String url = "jdbc:informix-sqli"
Connection con = DriverManager.getConnection(url, "login",
"password");
Statement stmt = con.createStatement();
//retrieval of values
(...)
}
stmt.close();
con.close();
} catch(SQLException ex) {
System.err.println("SQLException: " + ex.getMessage());
}

On JDBC dbping tab is written "This Utility assumes that you have a JDBC
driver installed and a CLASSPATH set before running DBPING"
a) What do they mean by having a JDBC driver installed? Isn't this driver
installed when I installed Informix-SDK? If not, how can I get it?
b) Do I have to do something like I did to the ODBC driver (by creating and
configuring a
DSN)? Where and how?
c) I know CLASSPATH system variable isn't set. Should I set it in my system?
By what value? By a path within Informix-SDK folders? Should CLASSPATH be
set anywhere else (e.g. setnet32)?
I suspect the problem is in my CLASSPATH system variable, but I don't know
how to set it. Or, perhaps, the strings I'm using aren't correct.
Can Anyone help?

Thanks in advance,
Jorge Cecilio

Your post is quite long.

A ClassNotFoundException is simply java telling u it cannot find a class
that u are trying to load, in this case: com.informix.jdbc.IfxDriver.

I assume this class is in a jar.
U can use the system classpath to include the path to this jar, or use
the -cp option from java.exe to specify where the jar resides.

For example, if your informix driver is located in a jar called
informix.jar, residing in the same directory as where u call java.exe to
start your application, the command would be:
java -cp informix.jar <your.class>

hth

Stijn