10

I'm using Play! 1.2.4 and PostgreSQL 9.1. I created a table with a created_at column, of type: timestamp without time zone. It has a default value of now().

The problem comes when I fetch data using my Entity class for this table. The createdAt field is always coming back null. Here is the field definition:

@Column(name="created_at", insertable=false)
public java.sql.Date createdAt;

All the other fields are populated correctly. I have tried changing the field type to a Date, Calendar, Timestamp, etc., and tried adding a @Timestamp annotation. But no combination has proved successful.

Thanks in advance for any help!

For reference, here is the DDL I used to create the table.

CREATE TABLE Users
(
  id serial     NOT NULL,
  username text NOT NULL,
  email text    NOT NULL,
  password_hash text NOT NULL DEFAULT 0,
  created_at timestamp without time zone DEFAULT now(),
  CONSTRAINT Users_pkey PRIMARY KEY (id),
  CONSTRAINT Users_username_key UNIQUE (username)
);

Update: I think the problem has to do with using JPA to insert a record. The database populates a default value of now() for created_at, but somehow Hibernate doesn't know about it when fetching that row.

If I query for a row that already existed, the createdAt field is populated correctly! OK... this narrows down the problem.

slattery
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4 Answers4

15

I didn't solve the problem exactly, but I worked around it.

Instead of having the database supply the default value of now(), I expressed it in JPA with @PrePersist:

@Column(name="created_at", nullable=false)
@Temporal(TemporalType.TIMESTAMP)
public Date createdAt;

@PrePersist
protected void onCreate() {
    createdAt = new Date();
}

That works fine! Inspiration taken from this answer. I'm still not sure why Hibernate didn't get updated with the default value that was applied in the database. It was stuck thinking the value was still null.

Community
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slattery
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3

Try this:

@Column(name="create_at", insertable=false)
@Temporal(TemporalType.TIMESTAMP)
private Date createAt;
Anderson Carniel
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  • I tried it, but no go. The field is still coming back null from the database. – slattery Dec 16 '11 at 00:59
  • Try this then `@Column(name="create_at", insertable=false, nullable=false)` – Anderson Carniel Dec 16 '11 at 01:06
  • How is your query? or try this too: `@Column(name="create_at", insertable=false, columnDefinition = "now()")` – Anderson Carniel Dec 16 '11 at 01:09
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    The table is already defined in the database. I'm not using JPA DDL to create it at runtime. I can use JPA to insert a row and `created_at` is automatically set to now() in the database. But when I fetch the row, all of the fields are present, except the createdAt field is null. Somehow the `timestamap` database value is not being converted. – slattery Dec 16 '11 at 01:33
  • Read this http://www.java2s.com/Tutorial/Java/0355__JPA/TemporalTypeTIMESTAMP.htm use the `java.util.Date` or `java.util.Calendar`. Hope this help – Anderson Carniel Dec 16 '11 at 01:57
  • Thanks for the suggestions. Turned out the problem was more with Hibernate not noticing that the database had supplied a value for `created_at`... I'm still not sure how to get it to notice that. – slattery Dec 16 '11 at 11:45
0

You need to detach and fetch entity from db. Insert statement does not contain created_at field so it's not managed by JPA at the time of creation. In repository it would look like this:

@Transactional
public Log save(Log log) {
    this.em.persist(log);
    this.em.detach(log);
    return this.em.find(Log.class, log.getId());
}
norbertas.gaulia
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0

Just in case, if the class where you fill the field definition is a master class, which all the other class extends it, don't forget to define it with the annotation:

import javax.persistence.MappedSuperclass;

@MappedSuperclass
public class MySuperClass {}
ssuperczynski
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Aquarius
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