I'm using Hibernate as the persistance layer for a Web Service through EJBs. I have some columns that are Oracle BLOBs but all I want the user to see is a String. I wrote a custom user type which maps the Blob to a String, and for retrieval of data it works correctly. However, when I try to update or insert I get a cast exception insice the oracle driver. It seems that Hibernate.createBlob creates a hibernate blob instance while OraclePreparedStatement.setBlob requires oracle.sql.BLOB.

Does anyone have any experience solving this problem? Do I just have to create an Oracle BLOB explicitly and ignore cross database functionality?

The custom class is below:

************ BEGIN CODE ******************
public class BlobString implements UserType {
public int[] sqlTypes() {
return new int[] { Types.BLOB };
}

public Class returnedClass() {
return String.class;
}


public boolean equals(Object x, Object y){
return x.equals( y );
}

public Object nullSafeGet(ResultSet rs, String[] names, Object owner)
throws HibernateException, SQLException {

Blob blob = rs.getBlob(names[0]);
if ( null == blob )
return null;

byte bytes[] = blob.getBytes( 1 , (int)blob.length() );
String data = new String(bytes);

return data;
}

public void nullSafeSet(PreparedStatement st, Object value, int index)
throws HibernateException, SQLException {

byte bytes[] = ((String)value).getBytes() ;

st.setBlob( index, Hibernate.createBlob( bytes ) );
}

public Object deepCopy(Object value) {
if (value == null)
return null;

return new String ( (String)value ) ;
}

public boolean isMutable() {
return true;
}

}

************ END CODE *******

This is the error Message:

java.lang.ClassCastException
at oracle.jdbc.driver.OraclePreparedStatement.setBlob(OraclePreparedStatement.java:1446)
at org.jboss.resource.adapter.jdbc.WrappedPreparedStatement.setBlob(WrappedPreparedStatement.java:680)
at com.doubleclick.util.BlobString.nullSafeSet(BlobString.java:47)


Thanks for your help.
-Eliot

Hibernate.createClob() is for use with a property of type "clob" ONLY!!

I used Hibernate.createBlob(), not Clob.

I was able to work areound it by using
st.setBytes - though I'm not sure this will work with all Databases.