How to set read-only columns in Hibernate?

问题

I don't know how to force read-only columns in Hibernate.

I would like to set idgroup as read only column. Even if I set insertable=false and updatable=false, in the hibernate SQL I can read:

Hibernate: insert into groups (description, name, account_idaccount, idgroup) values (?, ?, ?, ?)

but I would like to obtain:

insert into groups (description, name, account_idaccount) values (?, ?, ?)

Here are my classes:

@Entity
@Table(name = "groups")
public class Group implements java.io.Serializable {

private static final long serialVersionUID = -2948610975819234753L;
private GroupId id;
private Account account;
private String name;
private String description;

@EmbeddedId
@AttributeOverrides({@AttributeOverride(name = "idgroup", column = @Column(name = "idgroup", insertable = false)),
        @AttributeOverride(name = "accountIdaccount", column = @Column(name = "account_idaccount", nullable = false))})
public GroupId getId() {
    return id;
}

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "account_idaccount", nullable = false, insertable = false, updatable = false)
public Account getAccount() {
    return account;
}

@Column(name = "description", length = 512)
public String getDescription() {
    return description;
}


@Column(name = "name", nullable = false, length = 128)
public String getName() {
    return name;
}
..
}

@Embeddable
public class GroupId implements java.io.Serializable {

private int idgroup;
private int accountIdaccount;

@Column(name = "idgroup", insertable= false, updatable= false)
public int getIdgroup() {
    return this.idgroup;
}


@Column(name = "account_idaccount", nullable = false)
public int getAccountIdaccount() {
    return this.accountIdaccount;
}
..
}

I would like to have a read only column for idgroup because I can exploit the id auto-generation of the DBMS, I do not want to use the key auto-generation in Hibernate because it is not cluster-safe.

回答1:

I think you can mark an @Column annotation as updatable=false

回答2:

Easy: @Column(insertable = false, updatable = false)

回答3:

I was able to achieve this by using 2 DAO objects. I know it may not be preferred, but I didn't see another way around it. Setting the field to insertable=false and updatable=false do not remove the columns from the insert SQL so Postgres will not invoke the default action to populate those column values.

   // GroupWrite

   @Entity
   @Table(name = "group")
   public class GroupWrite {

      @Id
      @Column(name = "account")
      private Account account;

      @Column(name = "name")
      private String name;

      @Column(name = "description")
      private String description;


      /* Getters and Setters */
  }

   // GroupRead

   @Entity
   @Table(name = "group")
   public class GroupRead {

      @EmbeddedId
      @Column(name = "id")
      private GroupId id;

      @Column(name = "account")
      private Account account;

      @Column(name = "name")
      private String name;

      @Column(name = "description")
      private String description;


      /* Getters and Setters */
  }

Then you need to use the GroupRead when using select queries and GroupWrite when doing insert or update queries.

If you want to use attributes from both in a common way you can implement an interface that describes the overlapping fields.

   public interface Group {

        Account getAccount();

        void setAccount(Account account);
   }

   public class GroupWrite implements Group {...}

   public class GroupRead implements Group {...}

Hope this helps.

回答4:

The solution is using wrapper classes, such as Integer, not primitive types like int. When Hibernate will get a null pointer it will delegate the generation of the id to the DBMS.

回答5:

@ReadOnlyProperty annotation will help you in this case.

来源：https://stackoverflow.com/questions/14626341/how-to-set-read-only-columns-in-hibernate

标签

java

database

hibernate

orm

relational-database