Roger,
See:
http://www.oracle.com/technology/tech/java/sqlj_jdbc/htdocs/jdbc_faq.html#08_01
Specifically:
Simple Data Types What is going on with DATE and TIMESTAMP?
This section is on *simple* data types. :-)
Prior to 9.2, the Oracle JDBC drivers mapped the DATE SQL type to
java.sql.Timestamp. This made a certain amount of sense because the
Oracle DATE SQL type contains both date and time information as does
java.sql.Timestamp. The more obvious mapping to java.sql.Date was
somewhat problematic as java.sql.Date does not include time information.
It was also the case that the RDBMS did not support the TIMESTAMP SQL
type, so there was no problem with mapping DATE to Timestamp.
In 9.2 TIMESTAMP support was added to the RDBMS. The difference between
DATE and TIMESTAMP is that TIMESTAMP includes nanoseconds and DATE does
not. So, beginning in 9.2, DATE is mapped to Date and TIMESTAMP is
mapped to Timestamp. Unfortunately if you were relying on DATE values to
contain time information, there is a problem.
There are several ways to address this problem:
*
Alter your tables to use TIMESTAMP instead of DATE. This is
probably rarely possible, but it is the best solution when it is.
*
Alter your application to use defineColumnType to define the
columns as TIMESTAMP rather than DATE. There are problems with
this because you really don't want to use defineColumnType unless
you have to (see What is defineColumnType and when should I use
it?
<http://www.oracle.com/technology/tech/java/sqlj_jdbc/htdocs/jdbc_faq.html#06_01>).
*
Alter you application to use getTimestamp rather than getObject.
This is a good solution when possible, however many applications
contain generic code that relies on getObject, so it isn't always
possible.
*
Set the V8Compatible connection property. This tells the JDBC
drivers to use the old mapping rather than the new one. You can
set this flag either as a connection property or a system
property. You set the connection property by adding it to the
java.util.Properties object passed to DriverManager.getConnection
or to OracleDataSource.setConnectionProperties. You set the system
property by including a -D option in your java command line.
java -Doracle.jdbc.V8Compatible="true" MyApp
Oracle JDBC 11.1 fixes this problem. Beginning with this release the
driver maps SQL DATE columns to java.sql.Timestamp by default. There is
no need to set V8Compatible to get the correct mapping. V8Compatible is
strongly deprecated. You should not use it at all. If you do set it to
true it won't hurt anything, but you should stop using it.
Although it was rarely used that way, V8Compatible existed not to fix
the DATE to Date issue but to support compatibility with 8i databases.
8i (and older) databases did not support the TIMESTAMP type. Setting
V8Compatible not only caused SQL DATE to be mapped to Timestamp when
read from the database, it also caused all Timestamps to be converted to
SQL DATE when written to the database. Since 8i is desupported, the 11.1
JDBC drivers do not support this compatibility mode. For this reason
V8Compatible is desupported.
As mentioned above, the 11.1 drivers by default convert SQL DATE to
Timestamp when reading from the database. This always was the right
thing to do and the change in 9i was a mistake. The 11.1 drivers have
reverted to the correct behavior. Even if you didn't set V8Compatible in
your application you shouldn't see any difference in behavior in most
cases. You may notice a difference if you use getObject to read a DATE
column. The result will be a Timestamp rather than a Date. Since
Timestamp is a subclass of Date this generally isn't a problem. Where
you might notice a difference is if you relied on the conversion from
DATE to Date to truncate the time component or if you do toString on the
value. Otherwise the change should be transparent.
If for some reason your app is very sensitive to this change and you
simply must have the 9i-10g behavior, there is a connection property you
can set. Set mapDateToTimestamp to false and the driver will revert to
the default 9i-10g behavior and map DATE to Date.
If possible, you should change your column type to TIMESTAMP instead of
DATE.
-Richard
Roger Voss wrote:
I posted following question/problem on stackoverflow, so if anyone
knows a resolution, would be good to see it answered there:
Oracle SQL DATE conversion problem using iBATIS via Java JDBC
<http://stackoverflow.com/questions/383783/oracle-sql-date-conversion-problem-using-ibatis-via-java-jdbc>
Here's the problem description:
I'm currently wrestling with an Oracle sql DATE conversion problem
using iBATIS from Java.
Am using the Oracle JDBC thin driver ojdbc14 version 10.2.0.4.0.
iBATIS version 2.3.2. Java 1.6.0_10-rc2-b32.
The problem revolves around a column of DATE type that is being
returned by this snippet of SQL:
SELECT *
FROM TABLE(pk_invoice_qry.get_contract_rate(?,?,?,?,?,?,?,?,?,?))
order by from_date
The package procedure call returns a ref cursor that is being wrapped
in a TABLE to where is then easy to read the result set as though were
a select query against a table.
In PL/SQL Developer, one of the columns returned, FROM_DATE, of SQL
DATE type, has precision to time of day:
Tue Dec 16 23:59:00 PST 2008
But when I access this via iBATIS and JDBC, the value only retains
precision to day:
Tue Dec 16 12:00:00 AM PST 2008
This is clearer when displayed like so:
Should have been:
1229500740000 milliseconds since epoch
Tuesday, December 16, 2008 11:59:00 PM PST
But getting this instead:
1229414400000 milliseconds since epoch
Tuesday, December 16, 2008 12:00:00 AM PST
(as instance of class java.sql.Date)
No matter what I try, I am unable to expose the full precision of this
DATE column to be returned via Java JDBC and iBATIS.
What iBATIS is mapping from is this:
FROM_DATE : 2008-12-03 : class java.sql.Date
The current iBATIS mapping is this:
<result property="from_date" jdbcType="DATE" javaType="java.sql.Date"/>
I've also tried:
<result property="from_date" jdbcType="DATETIME"
javaType="java.sql.Date"/>
or
<result property="from_date" jdbcType="TIMESTAMP"
javaType="java.sql.Timestamp"/>
But all attempted mappings yield the same truncated Date value. It's
as though JDBC has already done the damage of loosing data precision
before iBATIS even touches it.
Clearly I'm loosing some of my data precision by going through JDBC
and iBATIS that is not happening when I stay in PL/SQL Developer
running the same SQL snippet as a test script. Not acceptable at all,
very frustrating, and ultimately very scary.
