org.hibernate.Session sess = sessionFactory.openSession();
String statement = "FROM TABLE WHERE ..."
org.hibernate.Query query = sess.createQuery(statement);
YourTableObject entry = null;

// get the specific entry in the database
entry = (YourTableObject) query.uniqueResult();
// set your value(s) via selfmade function(s) in the entry-object
entry.setValue("...");
...

//begin transaction
org.hibernate.Transaction tx = sess.beginTransaction();
//save changes
sess.save(entry);
// commit changes
tx.commit();
//close the session
sess.close();