I have these two classes
class Source {
// mapped to TIMESTAMP
#Version
#Column(columnDefinition="TIMESTAMP(3) DEFAULT '2016-01-01'")
Instant myInstant;
}
class Destination {
// mapped to DATETIME
#Basic(optional=true)
Instant myInstant;
}
When using Hibernate, I assign
destination.myInstant = source.myInstant;
and then the stored value is smaller by one hour than the original - both according to the command line MySQL client and in Java. My current timezone is UTC+1, so the reason is obviously a timezone conversion.
There are a few places where this can be fixed, but I'm looking for the best practice. The server should work world-wide, so it should continue to use UTC internally, right?
Should I just change the column type to TIMESTAMP? Then, why does Instant by default map to DATETIME?
According to this article, Instant does map to TIMESTAMP, but in my case it did not. Why?
If you want to work with timezones and Java 8 I would recommend using ZonedDateTime or OffsetTimeZone (the latter being prefered when working with Hibernate). For older versions use Calendar.
When you instance it should go by default with the timezone of your computer.
Check if the database is timestamp with or without timezone.
The default you set is also without timezone, and if it is "with timezone" it should automatically add the database's offset.
I hope some of this works. Here's how I did in one of my projects.
#Column(name = "registration_time")
private OffsetDateTime registrationTime;
[...]
subscriber.setRegistrationTime(OffsetDateTime.now());
In MySQL 5 & above, TIMESTAMP values are converted from the current time zone to UTC for storage, and converted back from UTC to the current time zone for retrieval. This occurs only for the TIMESTAMP data type but not for DATETIME. This is the reason you are seeing the difference while assigning a TIMESTAMP to DATETIME. So, having both the columns of same type should work. Hibernate by default maps InstantType to database TIMESTAMP type. Though you could use it for both TIMESTAMP and DATETIME in MYSQL, they are handled differently.
Related
I am using hibernate + spring and want to store/load timestamps in UTC. I've read that I should add a property, so I added this to my application.properties
spring.jpa.properties[hibernate.jdbc.time_zone]=UTC
This worked for one part of the problem - now dates are saved in utc in the database. But when I retrieve timestamps, they are transformed into default timezone. How can I fix this without setting default time zone to UTC?
The property of the entity has type LocalDateTime.
I ran the code, and noticed that the proper result set method is used during get(the one that accepts calendar) with instance that has zone info storing UTC. But after setting calendar's values to the one retrieved from the database, the calendar is transformed into Timestamp with this code
Timestamp ts = new Timestamp(c.getTimeInMillis());
In debug mode, I see that ts stores cdate field with value of timestamp in default time zone(not UTC).
First of all, if we are talking about Hibernate 5 (5.2.3 - 5.6.x if to be precise) the purpose of hibernate.jdbc.time_zone setting is not to give the ability for application developer to implement some kind of sophisticated date/time logic, but to synchronize persistence provider with underlying database, that is clearly stated in the corresponding CR:
Currently my database has implicit date times in UTC. No zoned data is appended to the end of the string (e.g. "2013-10-14 04:00:00").
When Hibernate reads this as a ZonedDateTime, it incorrectly reads it in as EST, as that is the TimeZone of the JVM.
It would be nice to be able to specify the TimeZone of a field by an annotation perhaps.
basically: you definitely need to set up hibernate.jdbc.time_zone if (mine: and only if) SQL statement like SELECT SYSDATE FROM DUAL (SELECT LOCALTIMESTAMP for PostgreSQL, etc) returns something, what you do not expect, in that case Hibernate will start adjusting non-timezone-aware JDBC data to something more or less reliable for application - that is exactly what you are observing (when I retrieve timestamps, they are transformed into default timezone)
At second, any speculations around JSR-310 and JDBC 4.2 (like for timezone-aware java types you need to define DB columns as timestamp with time zone), are not correct in case of Hibernate 5, that is mentioned in the corresponding CR as well:
The whole idea of "stored TZ" really depends on how the database/driver treats TIMESTAMP and whether it supports a "TIMESTAMP_WITH_TIMEZONE" type. I personally think it is a huge mistake to save the specific TZ differences to the DB, so I would personally continue to not support TIMESTAMP_WITH_TIMEZONE types. This would mean we never have to bind the Calendar because we could simply convert the value to to the JVM/JDBC TZ ourselves. Specifically I would suggest that we (continue to) assume that the driver has been set up such that the same TZ is used when ...
And indeed, if you try to find usage of java.sql.Types#TIMESTAMP_WITH_TIMEZONE in Hibernate 5 sources you will find nothing, just because that time Hibernate developers didn't get a common opinion about how timezone conversions should work in cases of different Java versions, Java types, DB engines and JDBC drivers (they are developing the most popular (mine: the only one) JPA implementation, that is definitely not the same as develop microservice), however, there are a lot of related changes in Hibernate 6 (check TimeZoneStorageType for example). In Hibernate 5 all timezone conversion logic passes through TimestampTypeDescriptor:
#Override
protected X doExtract(ResultSet rs, String name, WrapperOptions options) throws SQLException {
return options.getJdbcTimeZone() != null ?
javaTypeDescriptor.wrap( rs.getTimestamp( name, Calendar.getInstance( options.getJdbcTimeZone() ) ), options ) :
javaTypeDescriptor.wrap( rs.getTimestamp( name ), options );
}
and as you can see, Hibernate 5 just gives a hint to JDBC driver, how the last should process #getTimestamp call:
Retrieves the value of a JDBC TIMESTAMP parameter as a java.sql.Timestamp object, using the given Calendar object to construct the Timestamp object. With a Calendar object, the driver can calculate the timestamp taking into account a custom timezone and locale. If no Calendar object is specified, the driver uses the default timezone and locale.
in regard to your case:
you either need to use timezone-aware java types (ZonedDateTime/OffsetDateTime, or even Instant) or code your own Hibernate type, which will handle timezone conversions - that is not so hard as it might seem.
we can also set it up` per-session basis:
session = HibernateUtil.getSessionFactory().withOptions()
.jdbcTimeZone(TimeZone.getTimeZone("UTC"))
.openSession();
My database timezone was in UTC and in my application timezone I solved this problem by having both the Entity and the table have a date in UTC so that there will need to be no conversion between them. Then I did the conversions between timestamps in code in the getters and setters. Then I think you do it manually.
Setter and getter for that field:
public void setCreatedDate(LocalDateTime createdAt)
{
this.createdAt = createdAt.atZone(ZoneId.systemDefault()).withZoneSameInstant(ZoneOffset.UTC).toLocalDateTime();
}
public LocalDateTime getCreatedDate()
{
return createdAt.atZone(ZoneId.systemDefault()).withZoneSameInstant(ZoneOffset.UTC).toLocalDateTime();
}
As alluded to be Andrey in his answer, in Hibernate 6 the way to normalize dates/times to UTC is to use the java.time types OffsetDateTime or ZonedDateTime, and either:
annotate the field #TimeZoneStorage(NORMALIZE_UTC), or
set the property hibernate.timezone.default_storage=NORMALIZE_UTC.
I'm not very certain what you mean about using LocalDateTime here. What would it even mean to normalize a local datetime to UTC? That statement just doesn't really make sense: you can't move a local datetime to a new time zone because it doesn't have an associated time zone to begin with.
I think what you mean is that your "local" date times are actually zoned datetimes in the current JVM time zone. But if that's the case, it's very easy to use localDateTime.atZone(ZoneId.systemDefault()) to represent that situation correctly.
I have some Dates stored in Oracle with Oracle's TIMESTAMP(3) as its datatype. Now I'm writing a Spring boot app to read those values back. The code is like:
HibernateCallback callback = new HibernateCallback() {
public Object doInHibernate(Session session) throws HibernateException {
Query query = session.createSQLQuery("SELECT date_field FROM some_table WHERE some_conditions");
return query.list();
}
};
So:
List results = (List)getHibernateTemplate().execute(callback);
// suppose there's only one row and one column returned
Timestamp ts = result.get(0)[0];
returns me the Java Timestamp object automatically created by Hibernate. The problem is that, when constructing the object, it ignores the timezone stored in Oracle, but instead uses JVM's default timezone. I tested is by setting different timezones for the JVM, and each time it generates a different timestamp.
It's obviously wrong. The Date should be unique on the time line. It shouldn't depend on JVM's timezone. I'm wondering what's the correct way to include the DB's timezone info when parsing the date. Right now it seems it's just using the String representation stored in Oracle and parse it with JMV's timezone. I'm using Hibernate 4.3.4.Final.
PS: The actual query is high customized so I have to write raw SQL.
Basically, that's not even an issue with Hibernate but with JDBC. By default, JDBC Driver will use system time zone on which JVM is running. If you are connecting to the DB server at a different time zone or even if you want to be independent of the current timezone of the system it is a good idea to set JDBC Time Zone explicitly.
You can use hibernate.jdbc.time_zone property to set the timezone or do it at runtime via.
session = sessionFactory.withOptions()
.jdbcTimeZone(TimeZone.getTimeZone("UTC"))
.openSession();
Also for Oracle, I would say you can use the TIMESTAMP WITH LOCAL TIME ZONE which will respect you JDBC client time zone.
The problem is with Oracle column data type you are using, If you go to official oracle docs, link, you will notice the TIMESTAMP doesn't respect timezone, so you should go with with either TIMESTAMP WITH TIME ZONE or TIMESTAMP WITH LOCAL TIME ZONE.
It seems the issue is with few concepts of date handling
Dates in DB should be in UTC, if they are to be used in multiple timezone.
Java program should convert the dates to required timezone.
If you take your date in database as based on UTC, and then check the output of your hibernate query, you should see that date is changed as per JVM's timezone.
If you want the same date back (as was in DB), maybe you should convert the date to UTC timezone.
Now, you can do either of following:
Set the JVM's timezone same as the database record timezone. Not recommended
Change your dates in database as per UTC, and let the dates be changed to JVM's timezone. Recommended
I am unable to find a way to read timezone value in PostgreSQL column of type timestamp with time zone.
JDBC offers method java.sql.ResultSet#getTimestamp(int, java.util.Calendar)
but I must provide my own calendar. I have see no way to obtain that calendar from timestamp field I am reading.
I am working on system that stores time data of multiple timezones. I need to save data with timezone information, and be able to read that timezone back from database.
Is it possible without hacks like
storing timezone value in another field
storing date as string, like 'Wed 17 Dec 07:37:16 1997 PST'
I am using JDBC 41 (JDBC4 Postgresql Driver, Version 9.4-1201), java 8.
The PostgreSQL documentation here says that:
For timestamp with time zone, the internally stored value is always in UTC (Universal Coordinated Time, traditionally known as Greenwich Mean Time, GMT).
So there is no need to "store the time zone [that corresponds to the timestamp value]" per se; the timestamp with time zone values are always stored as UTC.
Also, there is no need to "obtain the Calendar from the timestamp field". The purpose of the Calendar is for you to define the particular timezone that you want to work with in your Java application.
In other words, timestamp with timezone does not store values from various timezones (e.g., some in EST, others in PST, etc.), it converts everything to UTC when the timestamp values are inserted.
Accepted answer is true and accurate. timestamp with time type does not store timezone information in the field, and it is not possible to extract it.
If interested in timezone of the timestamp, it must be stored in separately (in other field, or in custom column type).
At first glance, it looks like that timezone may be extracted from timestamp with timezone using function extract(timezone from field), but it is not the case.
That function just gives 'time zone offset from UTC, measured in seconds'. Important (and not stated in documentation) part is that the offset is measured from current timezone (set by session SET SESSION TIME ZONE, or server timezone if not set). It is not offset that was used when saving field.
I'm storing two dates in the PostgreSQL database. First, is the data of visit of a webpage, and the second date is the date of last modification of the webpage(this is get as a long).
I have some doubts what is the best strategy to store these values.
I only need day/month/year and hour:seconds and this will only for statistical proposes.
So, some doubts:
is best store as long and convert on recover of information or store in the data format above?
is best set the date of visit on the software or in the insertion in the database?
in Java, how are the best classes to handle dates?
Any strategy for storing date-and-time data in PostgreSQL should, IMO, rely on these two points:
Your solution should never depend on the server or client timezone setting.
Currently, PostgreSQL (as most databases) doesn't have a datatype to store a full date-and-time with timezone. So, you need to decide between an Instant or a LocalDateTime datatype.
My recipe follows.
If you want to record the physical instant at when a particular event ocurred, (a true "timestamp" , typically some creation/modification/deletion event), then use:
Java: Instant (Java 8 , or Jodatime).
JDBC: java.sql.Timestamp
PostgreSQL: TIMESTAMP WITH TIMEZONE (TIMESTAMPTZ)
(Don't let PostgreSQL peculiar datatypes WITH TIMEZONE/WITHOUT TIMEZONE confuse you: none of them actually stores a timezone)
Some boilerplate code: the following assumes that ps is a PreparedStatement, rs a ResultSet and tzUTC is a static Calendar object corresponding to UTC timezone.
public static final Calendar tzUTC = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
Write Instant to database TIMESTAMPTZ:
Instant instant = ...;
Timestamp ts = instant != null ? Timestamp.from(instant) : null;
ps.setTimestamp(col, ts, tzUTC); // column is TIMESTAMPTZ!
Read Instant from database TIMESTAMPTZ:
Timestamp ts = rs.getTimestamp(col,tzUTC); // column is TIMESTAMPTZ
Instant inst = ts !=null ? ts.toInstant() : null;
This works safely if your PG type is TIMESTAMPTZ (In that case, the calendarUTC has no effect in that code ; but it's always advisable to not depend on defaults timezones).
"Safely" means that the result will not depend on server or database timezone, or timezones information: the operation is fully reversible, and whatever happens to timezones settings, you'll always get the same "instant of time" you originally had on the Java side.
If, instead of a timestamp (an instant on the physical timeline), you are dealing with a "civil" local date-time (that is, the set of fields {year-month-day hour:min:sec(:msecs)}), you'd use:
Java: LocalDateTime (Java 8 , or Jodatime).
JDBC: java.sql.Timestamp
PostgreSQL: TIMESTAMP WITHOUT TIMEZONE (TIMESTAMP)
Read LocalDateTime from database TIMESTAMP:
Timestamp ts = rs.getTimestamp(col, tzUTC); //
LocalDateTime localDt = null;
if( ts != null )
localDt = LocalDateTime.ofInstant(Instant.ofEpochMilli(ts.getTime()), ZoneOffset.UTC);
Write LocalDateTime to database TIMESTAMP:
Timestamp ts = null;
if( localDt != null)
ts = new Timestamp(localDt.toInstant(ZoneOffset.UTC).toEpochMilli()), tzUTC);
ps.setTimestamp(colNum,ts, tzUTC);
Again, this strategy is safe and you can sleep peacefully: if you stored 2011-10-30 23:59:30 , you'll retrieve those precise fields (hour=23, minute=59... etc) always, no matter what - even if tomorrow the timezone of your Postgresql server (or client) changes, or your JVM or your OS timezone, or if your country modifies its DST rules, etc.
Added: If you want (it seems a natural requirement) to store the full datetime specification (a ZonedDatetime: the timestamp together with the timezone, which implicitly also includes the full civil datetime info - plus the timezone)... then I have bad news for you: PostgreSQL hasn't a datatype for this (neither other databases, to my knowledge). You must devise your own storage, perhaps in a pair of fields: could be the two above types (highly redundant, though efficient for retrieval and calculation), or one of them plus the time offset (you lose the timezone info, some calculations become difficult, and some impossible), or one of them plus the timezone (as string; some calculations can be extremely costly).
java.time
It's not pretty but this is what worked for me with a ZonedDateTime instance using the new java.time framework in Java 8 and later (Tutorial):
ZonedDateTime receivedTimestamp = some_ts_value;
Timestamp ts = new Timestamp(receivedTimestamp.toInstant().toEpochMilli());
ps.setTimestamp(
1,
ts,
Calendar.getInstance(TimeZone.getTimeZone(receivedTimestamp.getZone()))
);
I had used java.util.Date in our code to store Date in arguments of my query. I was using Spring JPA and using #Query annotations. The implementation worked.
I have a wierd hibernate related issue while setting a date field in an entity.
The date is interpreted as UTC in the java program (i did a System.out to make sure the date assigned is in 'UTC'. However, when hibernate actually persists to the database, the date is converted to local time and stored)
ex. the value has been set in the entity setter as "2009-09-09 00:08:08" - GMT
the actual value persisted to the database is "2009-09-08 08:08:08" - eastern time US.
I am unable to find out where and why this is happening and how to prevent it. Thanks
P.S. I am using joda date library and annotate the field with
#org.hibernate.annotations.Type(type = "org.joda.time.contrib.hibernate.PersistentDateTime")
However, when hibernate actually persists to the database, the date is converted to local time and stored) ex. the value has been set in the entity setter as "2009-09-09 00:08:08" - GMT the actual value persisted to the database is "2009-09-08 08:08:08" - eastern time US.
Ok, first, whatever column type are you using to store your date in MySQL (TIMESTAMP or DATETIME), neither stores the time zone. From Re: Storing timezone with datetime:
TIMESTAMP is seconds since 1970, sitting in 4 bytes. It is stored in GMT. That is, the TZ offset is applied as you store a value, then reapplied when you fetch it. (...)
DATETIME is an 8-byte string of digits "yyyymmddhhmmss". (...)
And second, unless a buggy behavior, my understanding is that the conversion is supposed be done either by the server or by the JDBC driver depending on the the server time zone settings so that you don't get inconsistent data.
In both cases, my point is that storing "2009-09-09 00:08:08" - GMT or "2009-09-08 08:08:08" - eastern time US from Java should yield to the same value in the database.
However, it looks like a different conversion is done when displaying them. This begs the question: how did you actually check the value of the "persisted date". Does the "problem" occur in your SQL client? In Java code?
References
9.6. MySQL Server Time Zone Support
21.3.4.1. Driver/Datasource Class Names, URL Syntax and Configuration Properties for Connector/J
Bug #15604: TimeZone discarded storing java.util.Calendar into DATETIME
MySQL documentation for DateTime says "MySQL retrieves and displays DATETIME values in 'YYYY-MM-DD HH:MM:SS' format". That means mysql converts the 'milliseconds since epoch' to the above format. So now my question becomes, is timezone info also stored in mysql?
I've updated my initial answer (which was not totally accurate/exhaustive). Whether you're using DATETIME or TIMESTAMP, the answer is no.
Another observation I made is, the above date 'conversion' issue exists only when Im setting the date in the Java application. If I create a mysql trigger to update/set date using 'UTC_TIMESTAMP()', the date is displayed in the 'UTC' time.
The UTC_TIMESTAMP() function always returns the current UTC date and time.
What I'd like to know is:
How did you "reveal" the problem? With a SQL client or from Java?
What is the local time zone of the JVM?
What is the MySQL Server time zone?
What is the version of the MySQL JDBC Driver?
Could you do a test with raw JDBC?
In order to treat dates as UTC in the DB (for read/write), you can use this small open source library DbAssist. It uses a custom UtcDateType in order to map java.util.Date fields in your entities, so that they are treated by Hibernate as UTC in the DB. Since you are using JPA annotations, you would use the following dependency:
<dependency>
<groupId>com.montrosesoftware</groupId>
<artifactId>DbAssist-5.2.2</artifactId>
<version>1.0-RELEASE</version>
</dependency>
Applying the fix is easy, for example, when using Spring Boot, you have to make sure that you have #EnableAutoConfiguration annotation before the application class. If you are using another Hibernate version, just refer to github wiki to find the proper version of the fix and the installation guide. You can also read more about the time zone shift issue in this article.
This behaviour of Joda Time Contrib is fixed in my project Usertype for Joda Time and JSR310. See http://usertype.sourceforge.net/ which is practically otherwise a drop in replacement for JodaTime Hibernate.
I have written about this issue: http://blog.jadira.co.uk/blog/2010/5/1/javasqldate-types-and-the-offsetting-problem.html
Hope this helps,
Chris