Character Set Unknown issue in JBoss server

Hi,

I am not able to read String data from SQLInput stream of a customized database object.

Java object corresponding to customized row type is:

public class Excust implements SQLData {
public String numFact;
public String indFact;
public String dFacEmi;
public int mntImp;
public String devTit;

private static String SCHEMA_NAME_POSTFIX = ".EXOBJECT";

public Excust () {
initSchemaName();
}
private void initSchemaName() {
String schemaname = "OPSSCHEMANAME";
sql_type = schemaname;
}
public void readSQL(SQLInput stream, String type) throws SQLException {
sql_type = type;
numFact = stream.readString(); //It is read as ???-- Character Set Unknown
indFact = stream.readString(); //It is read as ???-- Character Set Unknown
dFacEmi = stream.readString(); //It is read as ???-- Character Set Unknown
mntImp = stream.readInt();
devTit = stream.readString(); //It is read as ???-- Character Set Unknown

}

public void writeSQL(SQLOutput stream) throws SQLException {

// champs à écrire dans l'ordre
stream.writeString(numFact.toString());
stream.writeString(indFact.toString());
stream.writeString(dFacEmi.toString());
stream.writeInt(mntImp);
stream.writeString(devTit.toString());
}

When I get the connection object using DriverManager i.e.
Class.forName("oracle.jdbc.driver.OracleDriver");
connection = DriverManager.getConnection(
"jdbc:oracle:thin:@21.78.233.76:1521:Databasename", "username",
"password");
I am able to get the data.

But using datasource in JBOSS I am not able to get the data saying "Character Set unknown".
Datasource code:

Context initContext = (Context) new InitialContext().
lookup("java:comp/env");
Hashtable params = new Hashtable();
params.put(Context.INITIAL_CONTEXT_FACTORY, org.jnp.interfaces.NamingContextFactory);
String providerURL = "21.78.233.76:1521";
params.put(Context.PROVIDER_URL, providerURL);
initContext = new InitialContext(params);
datasource = (DataSource) initContext.lookup("java:OracleDS");
initContext.close();
Connection connection = datasource.getConnection();

Our database is using WE8ISO8859P15 character set.

Can anybody please suggest why I am not able to get the data when I connect with datasource in JBOSS Server?

Thanks in advance.