Connection pooling in java

hi all..

i am tring to use connection pool with postgresql..but it give an Exception
when it is going to execute the line following.
InitialContext().rebind("DataSource", source)

the cord is as follow.

Jdbc3PoolingDataSource source = new Jdbc3PoolingDataSource();
source.setDataSourceName("A Data Source");
source.setServerName("localhost");
source.setDatabaseName("mmsc");
source.setUser("janaka");
source.setPassword("1234");
source.setMaxConnections(10);
try {
new InitialContext().rebind("DataSource", source);
}
catch (NamingException ex) {
System.out.println(ex.getMessage());
ex.printStackTrace();
}

the given exception is as follow....

javax.naming.NoInitialContextException: Need to specify class name in
environment or system property, or as an applet parameter, or in an
application resource file: java.naming.factory.initial
at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java
:645)
at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java
:247)
at javax.naming.InitialContext.getURLOrDefaultInitCtx(
InitialContext.java:284)
at javax.naming.InitialContext.rebind(InitialContext.java:367)
at MainClass.main(MainClass.java:29)

please help me to solve this..

--
...........Janaka Priyadarshana...........