Hello,

The java.util.Date and the java.sql.Date within the hibernate context is one of the most often asked question. It is without a doubt the most confusing. I am creating this thread hoping to gather all in one place the answers to this question.

Context:
a model has member variables using a java.util.Date
Date myDateOnly; //we only care about the Date not the time
Date myDateWithTime; //we want it all

the hbm.xml is defined as:
<property name="myDateOnly" column="my_date_only" type="java.util.Date" />
<property name="myDateWithTime" column="my_date_with_time" type="java.util.Date" />


the database underneath declares the type as:
my_date_only column is created as a DATE (mySQL mode)
my_date_only column is created as a DATETIME (mySQL mode)

Execution:
SimpleDateFormat dateFormatter = new SimpleDateFormat("yyyy-mm-dd");
Date dateOnly = dateFormatter.parse("2007/10/23");
Date dateWithTime = Calendar.getInstance().getTime();

model.setMyDateOnly(dateOnly);
model.setMyDateWithTime(dateWithTime);
model.save();

//imagine code to get a model back from db.
dateOnlyFromDb = model.getMyDateOnly();
dateWithTimeFromDb = model.getMyDateWithTime();

assertTrue(dateOnly.equals(dateOnlyFromDb));
assertTrue(dateWithTime.equals(dateWithTimeFromDb));

Now the question:
Both asserts fail. Why?

I made a typo: imagine the format is correct everywhere (ie. yyyy-mm-dd)

Try using type="date", type="time", or type="timestamp".

Once you correct this, your second assertion will probably still fail:
assertTrue(dateWithTime.equals(dateWithTimeFromDb));

Because you're dateWithTime was created with millisecond precision in the JVM and will probably come out of the DB with only "second" precision from the database. I'm not sure about this, but be forewarned.

(Also, a side critique, use assertEquals(dateWithTime, dateWithTimeFromDb) don't abuse assertTrue).

junit.framework.AssertionFailedError: expected:<Tue Oct 23 14:31:28 MST 2007> but was:<2007-10-23 14:31:28.0

The date in mySQL database is fine, I am using timestamp. Why does mySQL keeps returning the milliseconds when I don't want them. This is frustating.

I did the following changes:

the database underneath declares the type as:
my_date_only column is created as a DATE (mySQL mode)
my_date_only column is created as a TIMESTAMP (mySQL mode)

the hbm.xml is defined as:
<property name="myDateOnly" column="my_date_only" type="date" />
<property name="myDateWithTime" column="my_date_with_time" type="timestamp" />

When I compare the date from myDateWithTime I am getting:
junit.framework.AssertionFailedError: expected:<Tue Oct 23 14:31:28 MST 2007> but was:<2007-10-23 14:31:28.0

Why this extra .0 coming from the date created from the database entry?

Try comparing their times...
assertEquals(dateWithTime.getTime(), dateWithTimeFromDb.getTime());