Hello,

I have a problem, and please help, if you can.

Situation is:
I already have an application, and this application contains lots of hibernate domain objects with lots of relations. This version is called: 1.0

Now I would like to refactor almost all of the domains.
How can I change the database structure without data lose, and how can I copy the data between the old version and new version.
For example:

Version 1.0 Domains:
@Entity
class Class1 {
@Id
private Integer id;

@ManyToOne
private Class2 class2;

private String name;
}
@Entity
class Class2 {
@Id
private Integer id;

private String description;
}


New Version 2.0 Domains:
@Entity
class Class1 {
@Id
private Integer id;

// Change directions
@ManyToMany
private Set<Class2> class2Objects;

// private String name; // not in new version

// In Existing data, I would like to separate the name
private String firstName;
private String lastName;
}
@Entity
class Class2 {
@Id
private Integer id;

@ManyToMany
private Set<Class1> class1Objects;

private String description;

// This property data generate from code. In existing objects I must generate also.
private String uniqKey;
}

So How can I change the table structure without data loosing, and how can I convert/generate the existing data? Do it with SQL commands (ALTER TABLE ... UPDATE ...)

Is there any workflow how can I update the very different object domain structure?

Thanks for your help