when I first deploy my Bean to Jboss. Jboss auto create
database tabel.For some reason ,I change the structure of my Bean,this time I deploy my Bean,Jboss may tell me to remove the first tabel.But I have put some important data into first tabel.So how can I deploy my new Bean and not lose my old data?
You will have to transition the data by hand. There is no way for the server to know how to move the data.