primary key as as char

I have a table as a primary key with char(1) on the sql server using the jtds driver.

public class Situacao{

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "cod_sit_pedi_aval")
private Character codSitPediAval;

}

public class Pedido{

@ManyToOne
@JoinColumn(name = "cod_sit_pedi_aval")
private Situacao situacao;
}

Caused by: java.lang.AbstractMethodError
  at net.sourceforge.jtds.jdbc.JtdsPreparedStatement.setCharacterStream(JtdsPreparedStatement.java:1274)
  at org.jboss.jca.adapters.jdbc.WrappedPreparedStatement.setCharacterStream(WrappedPreparedStatement.java:1466)

How can I resolve this problem?