Oracle10g JDBC ojdbc14 DATE类型hibernate查询时分秒问题
一般的数据库中，DATE字段仅仅表示日期，不包括日期信息，而Oracle数据库中的DATE数据类型是包括日期、时间的，对于不同的Oracle jdbc驱动版本，对于该问题的处理都有些区别。

    最近项目中碰到此问题，用的是ORACLE 10G，时间字段因需求，设为了DATE类型，发现hibernate用native SQL 查询，显示不了时分秒，一看，原来是JDBC驱动自动把date映射为 java.sql.date，故截断了时分秒信息，如果你使用9i或者11g
的驱动程序，此问题不存在，但是Oracle10g的JDBC驱动，问题就来了，你会发现时间不见了！！！
   
网上看了资料，在oracle 官网Oracle JDBC FAQ 看到：

http://www.oracle.com/technology/tech/java/sqlj_jdbc/htdocs/jdbc_faq.html#08_01


引用

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 in the 9.2 through 10.2 drivers:

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?).

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 no