CODEWITHSUNDEEP
javahibernatejpaannotations
Benjamin
Benjamin

Reputation: 161

Complex Primary Key using Hibernate with Annotation

I would like to generate a custom ID for an object, depending on values already in database.

I know several questions were asked on that subject, but I can't figure a solution out...

Here is my class :

@Entity
class A {
    // primary key for table
    @GeneratedValue
    @Id
    private long tableId;

    // id -> should be generated as (1+ (max id of type 'type'))
    @Formula("1+(select t.id from mytable t where t.type=type)") 
    private long id;

    // type 
    private String type;
}

I thought of the @Formula annotation, but I can't get it work...

exception raised : 

java.sql.SQLException: Field 'id' doesn't have a default value

I'm not sure the @Formula is the good solution...

Does anybody has a clue of how I can make it work ?

Thanks a lot,

Ben

Upvotes: 2

Views: 856

Answers (2)

Benjamin
Benjamin

Reputation: 161

I solved my problem using a @PrePersist annotation.

@PrePersist
private void generateId() {

    if(id>0){
        return;
    }
    id=++type.lastChronoId;
    type.save();
}

with type modified to a Type class, containing the index of the last created object.

Upvotes: 0

bpgergo
bpgergo

Reputation: 16037

try this

@Formula(value = "(select t.id+1 from mytable t where t.type=type)") 
private long id;

Upvotes: 1

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