How to handle different date formats ?

Question

I'm currently writing an application that has to be compatible with different database backends.
But I have some problems with the date/time fields when using Oracle as a db backend:
After searching the forums, I found a solution for my "inserts" problem:
// This is needed because otherwise the db session will be reset with each jdbc call,
// ending the session and nullifying the ALTER SESSION command
con.setAutoCommit( false );
// set the date/time format to what we want it to be
result = stmt.executeQuery("ALTER SESSION SET NLS_DATE_FORMAT = 'dd/mm/yyyy hh24:mi:ss'");
res = stmt.executeUpdate(query);
Where query is something like "INSERT INTO DATE_TEST VALUES ('val1',"val2','val3','25/03/2004 15:59:44');
But when I want to retrieve this data, the timestamp is returned in another format:
result = stmt.executeQuery("SELECT * FROM DATE_TEST");
This gives me "2004-03-25 15:59:44.0" for the timestamp !
when I run exactly the same query in the Oracle SQL*Plus console, I get the correct format:
SQL> SELECT * FROM DATE_TEST;
VAL1 VAL2 VAL3 TIME
val1 val2 val3 25/03/2004 15:59:44
SQL>
I already tried the trick with the NLS_DATE_FORMAT before retrieving the data, but that doesn't seem to do anything.
Any ideas how I can manipulate the format of a DATE field for retrieval ?
Note:
This is what I use:
- Oracle 9i, Release 2 (9.2.0.1.0) for Windows (on windows 2000 Server)
- ojdbc14.jar (Oracle thin jdbc driver)
- j2sdk 1.4.2-04 for my application (currently running on windows server 2003 Enterprise, but is also tested on windows 2000, xp, linux, solaris)

Answer 1

well, in fact I wrote a "dbAdapter" which I use to let my application communicate with a database.
the method I use to retrieve data from the db just reads the resultset row by row, adding each row to a
vector.
each row is represented by a hashtable (colname - colvalue pairs).
Vector result = dbadapter.queryDB("SELECT * FROM DATE_TEST");
the method "query" looks like this:
public Vector queryDB(String query) {
Connection con = null;
ResultSet result = null;
ResultSetMetaData metadata = null;
Vector tableData = new Vector();
Statement stmt = null;
try { // Attempt to load the JDBC driver with newInstance
Class.forName(sDriver).newInstance();
catch (Exception e) { // error
logger.error(logPrefix + "Failed to load current driver.");
if (psStackTrace != null)
e.printStackTrace(psStackTrace);
return tableData;
} // end catch
try {
con = DriverManager.getConnection(sURL, sUsername, sPassword);
// stmt = con.createStatement(); // MySQL
stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_READ_ONLY); // TODO-ORACLE
catch (Exception e) {
logger.error(logPrefix + "problems connecting to " + sURL + ":" + e.getMessage());
if (psStackTrace != null)
e.printStackTrace(psStackTrace);
if (con != null) {
try {
con.close();
catch (Exception e2) {
return tableData;
} // end catch
// execute SQL commands
try {
result = stmt.executeQuery(query);
// first display some metadata
metadata = result.getMetaData();
int numcols = metadata.getColumnCount(); // How many columns?
result.last(); // Move to last row
int numrows = result.getRow();
Hashtable rowData = new Hashtable();
String colValue = "", colName = "";
Object o = null;
for (int a = 0; a < numrows; a++) {
result.absolute(a + 1); // go to row a in resultset
for (byte b = 0; b < numcols; b++) {
o = result.getObject(b + 1);
colName = metadata.getColumnName(b + 1);
if (o == null) {
colValue = "";
else {
colValue = o.toString();
rowData.put(colName, colValue);
tableData.add(rowData.clone());
rowData.clear();
// return result
return tableData;
catch (Exception e) {
logger.error(logPrefix + "problem with SQL sent to " + sURL + ":" + e.getMessage());
logger.debug(logPrefix + "sql: " + query);
if (psStackTrace != null)
e.printStackTrace(psStackTrace);
finally {
try {
stmt.close();
catch (Exception e) {
try {
con.close();
catch (Exception e) {
} // end finally clause
return tableData;
then I display the data using this code (output goes to a logfile):
for (int i = 0; i < result.size(); i++) {
Hashtable tmpResultTable = (Hashtable) result.elementAt(i);
Enumeration enum = tmpResultTable.keys();
while(enum.hasMoreElements()) {
String tmpKey = (String) enum.nextElement();
String tmpValue = (String) tmpResultTable.get(tmpKey);
logger.debug(logPrefix + "\t- " + tmpKey + "=" + tmpValue);
It is correct indeed that I want to keep it as vendor neutral as possible, because other databases will
be added in the (near) future (such as IBM's DB2)
I already thought about formatting it using the SimpleDateFormat class, but then I have to rewrite most
of the code in my dbAdapter, because it doesn't know anything about the field types.
It just launches standard SQL queries and returns the result back to the requesting object