sybase problème de connexion jdbc

je suis juste un débutant dans sybase. suis en train de faire une simple connexion jdbc à mon serveur sybase. à l'aide de code ci-dessous.

j'ai jcon3.jar dans mon classpath trop.

try {
        Class.forName("com.sybase.jdbc3.jdbc.SybDataSource");
        System.out.println("before connection");
        Connection conn = DriverManager.getConnection("jdbc:sybase:Tds:localhost:1326/db","butt","clear");
        System.out.println("after connection");
    } catch (Exception e) {
        e.printStackTrace();
    }

je ne suis pas capable d'atteindre ce que j'attends. ci-dessous est l'erreur que j'obtiens.

inside try
before connection
java.sql.SQLException: JZ00L: Login failed.  Examine the SQLWarnings chained to this exception for the reason(s).
at com.sybase.jdbc3.jdbc.ErrorMessage.raiseError(Unknown Source)
at com.sybase.jdbc3.tds.Tds.for(Unknown Source)
at com.sybase.jdbc3.tds.Tds.a(Unknown Source)
at com.sybase.jdbc3.tds.Tds.login(Unknown Source)
at com.sybase.jdbc3.jdbc.SybConnection.a(Unknown Source)
at com.sybase.jdbc3.jdbc.SybConnection.a(Unknown Source)
at com.sybase.jdbc3.jdbc.SybConnection.<init>(Unknown Source)
at com.sybase.jdbc3.jdbc.SybConnection.<init>(Unknown Source)
at com.sybase.jdbc3.jdbc.SybDriver.connect(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at com.risk.JDBC.TestJdbc.main(TestJdbc.java:19)
SQL Error : State=[JZ00L] JZ00L: Login failed.  Examine the SQLWarnings chained to this exception for the reason(s).
SQL Error : State=[JZ0IB] JZ0IB: The server's default charset of roman8 does not map to an encoding that is available in the client Java environment. Because jConnect will not be able to do client-side conversion, the connection is unusable and is being closed. Try using a later Java version, or try including your Java installation's i18n.jar or charsets.jar file in the classpath.
SQL Error : State=[JZ006] JZ006: Caught IOException: java.io.CharConversionException: java.io.UnsupportedEncodingException: hp-roman8