Question

I have a problem about the management of dates with milliseconds. I understand the need to use the TIMESTAMP to store milliseconds:

@Temporal(TIMESTAMP)
@Column(name="DATE_COLUMN", nullable = false)
@Override public java.util.Date getDate() { return this.date; }

But if I can’t compare this date to another instance of java.util.Date, unless I pay attention to the order of equals() call, because this.date instance is a java.sql.Timestamp. How to get a java.util.Date from JPA ? Because the date that comes from JPA, even if the method signature is a java.util.Date is actually an instance of java.sql.Timestamp.

java.util.Date newDate = new Date(this.date.getTime());
this.date.equals(newDate) == false
newDate.equals(this.date) == true

I’ve try to modify my method in the persistence class:

@Override
public Date getDate() {
  return this.date == null ? null : new Date(this.date.getTime());
}

It’s working, but it’s not efficient with lots of data.

There are other options :

• I could modify the design of my persistence class, using @PostLoad in order to create a java.util.Date from the persited date after I retrieve it.

• I wonder if I can not get a result using a ClassTransformer?

Have you ever been confronted with this problem? What I do not correctly? What is the best way to handle this problem?

Answer 1

java.sql.Timestamp overrides the compareTo(Date) method, so it should be no problem using compareTo(..)

In short – java.util.Date and java.sql.Timestamp are mutually comparable.

Furthermore, you can always compare the date.getTime(), rather than the objects themselves.

And even further – you can use a long field to store the date. Or even a DateTime (from joda-time)