HowTo: Replace values in Entity, best practice

Question

I was reading jsr-220 and now I have a question.
What is the best practice to replace values in an entity?
For example I have an entity Person:
@Table(name = "Person", schema = SCHEMA)
public class Person{
     @Id
     @GeneratedValue
     private int id;
     private String sourceUri;
       @ManyToMany(fetch=FetchType.EAGER, cascade={CascadeType.MERGE, CascadeType.REFRESH, CascadeType.PERSIST} )
     private List<Representative> representatives;
     @OrderBy("date")
     @ManyToMany(fetch=FetchType.EAGER, cascade={CascadeType.ALL}, mappedBy="person")
        private List<PersonAccessCounter> counter;
     @OneToMany(fetch=FetchType.EAGER, cascade={CascadeType.ALL}, mappedBy="person")
     private List<EducationLevel> educationLevels;
      //some other fileds + getters/setters
}As you can see, my Person has autoGenerated id. But also it has other "unformal" identity field: sourceUri
Imagine such situation:
I've persisted a Person. While system was in use, it's id points to some other entities. So I can't loose it.
Then, my special crawler gathered new info about person.
Using sourceUri of Person(crawler has provided it) I can select already persisted person from DB.
Now, my task is to completely remove some fields (this data must disappear from DB, totally, no orphaned links) from persisted person and replace them with values from new person gathered by crawler.
What's better?
1. Find persitedPerson using sourceUri
2. Replace some fields of persitedPerson with new values taken from crawledPerson.
3. em.merge(persistedPerson)
OR
1. Find persitedPerson using sourceUri.
2. Set some fields of persitedPerson to NULL
3. Merge persitedPerson
4. Set new values to persitedPerson taken from crawledPerson.
3. em.merge(persistedPerson)
Seems like the first variant is enough. It will fork fine if annotations were set correctly (cascade={CascadeType.ALL} and other)
Edited by: Holod on 10.11.2008 16:32
Edited by: Holod on 10.11.2008 16:46

Answer 1

I was reading jsr-220 and now I have a question.
What is the best practice to replace values in an entity?
For example I have an entity Person:
@Table(name = "Person", schema = SCHEMA)
public class Person{
     @Id
     @GeneratedValue
     private int id;
     private String sourceUri;
       @ManyToMany(fetch=FetchType.EAGER, cascade={CascadeType.MERGE, CascadeType.REFRESH, CascadeType.PERSIST} )
     private List<Representative> representatives;
     @OrderBy("date")
     @ManyToMany(fetch=FetchType.EAGER, cascade={CascadeType.ALL}, mappedBy="person")
        private List<PersonAccessCounter> counter;
     @OneToMany(fetch=FetchType.EAGER, cascade={CascadeType.ALL}, mappedBy="person")
     private List<EducationLevel> educationLevels;
      //some other fileds + getters/setters
}As you can see, my Person has autoGenerated id. But also it has other "unformal" identity field: sourceUri
Imagine such situation:
I've persisted a Person. While system was in use, it's id points to some other entities. So I can't loose it.
Then, my special crawler gathered new info about person.
Using sourceUri of Person(crawler has provided it) I can select already persisted person from DB.
Now, my task is to completely remove some fields (this data must disappear from DB, totally, no orphaned links) from persisted person and replace them with values from new person gathered by crawler.
What's better?
1. Find persitedPerson using sourceUri
2. Replace some fields of persitedPerson with new values taken from crawledPerson.
3. em.merge(persistedPerson)
OR
1. Find persitedPerson using sourceUri.
2. Set some fields of persitedPerson to NULL
3. Merge persitedPerson
4. Set new values to persitedPerson taken from crawledPerson.
3. em.merge(persistedPerson)
Seems like the first variant is enough. It will fork fine if annotations were set correctly (cascade={CascadeType.ALL} and other)
Edited by: Holod on 10.11.2008 16:32
Edited by: Holod on 10.11.2008 16:46