Jooq LocalDateTime fields use system timezone inst

问题:

I'm using jooq (v3.11.9) to access a MySQL database that is running in UTC time. I've using generated entities and am using JSR-310 time types. The option I'm using in my config:

<javaTimeTypes>true</javaTimeTypes>

My understanding is that the MySQLdatetime and timestamp types both map to LocalDateTime which makes sense as MySQL doesn't store timezone information with the times. However when I run queries on a machine in a different timezone (in my case EST) the dates are all in my local machine timezone even though the session timezone is UTC.

I've confirmed that the session timezone is UTC

dslContext.fetch("SELECT @@system_time_zone,  @@global.time_zone, @@session.time_zone;")

returns

|@@system_time_zone|@@global.time_zone|@@session.time_zone|
+------------------+------------------+-------------------+
|UTC               |SYSTEM            |SYSTEM             |
+------------------+------------------+-------------------+

Example of timezone conversion:

dslContext.select(MY_TABLE.EPOCH_DT_TM, MY_TABLE.CREATION_TIMESTAMP).from(MY_TABLE).limit(1).fetch()

+-----------------------+-----------------------+
|epoch_dt_tm            |creation_timestamp     |
+-----------------------+-----------------------+
|2019-04-18T13:57:39.163|2019-09-24T16:06:47.754|
+-----------------------+-----------------------+
// CAST to STRING PROPERLY USES SESSION TIMEZONE 
dslContext.select(MY_TABLE.EPOCH_DT_TM.cast(org.jooq.impl.SQLDataType.VARCHAR(100)), MY_TABLE.CREATION_TIMESTAMP.cast(org.jooq.impl.SQLDataType.VARCHAR(100))).from(MY_TABLE).limit(1).fetch()
+--------------------------+--------------------------+
|cast                      |cast                      |
+--------------------------+--------------------------+
|2019-04-18 17:57:39.163000|2019-09-24 20:06:47.754000|
+--------------------------+--------------------------+

The fields in my generated entities:

    public final TableField<MyTableRecord, LocalDateTime> EPOCH_DT_TM = createField("epoch_dt_tm", org.jooq.impl.SQLDataType.LOCALDATETIME, this, "");
    public final TableField<MyTableRecord, LocalDateTime> CREATION_TIMESTAMP = createField("creation_timestamp", org.jooq.impl.SQLDataType.LOCALDATETIME.nullable(false).defaultValue(org.jooq.impl.DSL.field("CURRENT_TIMESTAMP(6)", org.jooq.impl.SQLDataType.LOCALDATETIME)), this, "");

So my questions are:

1. Is this expected behavior? Shouldn't the record get populated with the raw (non timezoned) date in the table. Are the dates still getting converted to java.sql.Timestamp under the hood for some reason?

2. If this is expected behavior is there any way to ensure that you get dates in the session timezone regardless of the local timezone on the client machine? It is very hard to test locally if the behavior of the code is dependent on the machine timezone.

Thank you in advance for your help.

回答1:

I recently found that depending on the database driver being used, jOOQ can exhibit some strange behavior in DateTime parsing. jOOQ returns offset date time as Z (UTC) even though it's not

Specifically, in my case, using a different Postgres driver resulted in DefaultBinding.java receiving a calendar object that has a timestamp, but calling toString on it in order to parse. Turns out, toString does not print the timezone, then jOOQ inferred that it was in local time.

For me, the offending lines in DefaultBinding.java (I was using a timestamp with timezone) were:

else if (type == OffsetDateTime.class) {
    result = (T) offsetDateTime(ctx.resultSet().getString(ctx.index()));
}

You may be on a different line in that series of else ifs based on not having a time zone.

In my testing, I also found that changing the system time changed the result, but changing the session time did nothing.

Fortunately for me, a switch to the standard Postgres driver resolved the problem. If it didn't, I was going to look in to overloading the binding for OffsetDateTime to fix the use of toString and it's associated stripping of the relevant time zone. You may need to pursue that path, unfortunately, unless you too are using a SQL driver than could be upgraded or replaced. Or, you could store it with a timezone and then convert to the desired timezone when you load from the database.