The database I'm using is ORACLE 9.2.
I got an ClassCastExceptiontyied when trying to use Hibernate2 to
insert records to a table which contains Blob type columns.
It seems that hibernate2 is trying to use the setBlob method of
java.sql.PreparedStatement class. But the implementation of
ORACLE seems to cast the inputted Blob object into a ORACLE
specified Blob type object immediately.
That's why it leads to an ClassCastException.

My question is, does this mean that I cannot use that hibernate
to write a Blob type object to the ORACLE database at all?
Or there are some ways to avoid this problem?

By the way, as the cause of the problem is the implementation
of the setBlob method, it means that I cannot avoid this problem
even when I use JDBC directly.

I don't know WHAT you're doing, but if you use it as is intended, ie use type="blob", Hibernate will not call setBlob() when it is an instance created with Hibernate.createBlob(). It will call setBinaryStream() instead.

I have the same problem. I used the "Mapping a Blob to a byte[]"-solution
(http://hibernate.bluemars.net/73.html) and therefore have type="com.netikos.se.storeimpl.BinaryBlobType".

Well, here is a comment (by me), from the bottom of the page:
a mutable object.

I try to use byte[] <-> Blob also.
DB : PostgresSQL 7.3.1 under Linux

My table is

create table external_docs (
ext_id int4 not null,
report_id int4 null,
name varchar(200) not null,
value bytea not null,
content_type varchar(100) null,
create_date timestamp null,
constraint pk_external_docs primary key (ext_id),
constraint fk_external_relations_report foreign key (report_id)
references report (report_id)
on delete restrict on update restrict
);

I used original BinaryBlobType example and modificated :
public void nullSafeSet(PreparedStatement st, Object value, int index)
throws HibernateException, SQLException {
final byte[] buf = (byte[]) value;
ByteArrayInputStream in = new ByteArrayInputStream(buf);
st.setBinaryStream(index, in, buf.length);
}

But still i'm getting errors like this one:
Hibernate: select nextval ('ext_doc_seq')
Hibernate: insert into external_docs (name, content_type, value, report_id, create_date, ext_id) values (?, ?, ?, ?, ?, ?)
13:48:17,098 WARN JDBCExceptionReporter:38 - SQL Error: 0, SQLState: null
13:48:17,098 ERROR JDBCExceptionReporter:46 - ERROR: column "value" is of type bytea but expression is of type integer
You will need to rewrite or cast the expression

I've fixed this problem.
Using type="binary" and downloading the lastest version of jdbc drivers.