Wrong data type returned for date in jtds.jar

Question

I have a table on MS SQL Server with a column having data type as date. I am using jtds.jar for JDBC connection with DB. I am taking DatabaseMetaData from Connection. While checking columns from DatabaseMetaData, I observed that

int iType = rsMeta.getInt("DATA_TYPE");

returns Column type as java.sql.Types.VARCHAR which is a string and not date. but it also returns

String tmp = rsMeta.getString("TYPE_NAME");

type name as date.

But for Oracle, It returns the date datatype as java.sql.Types.DATE.

Why is such a difference?

Answer 1

This is a known JTDS bug, see http://sourceforge.net/p/jtds/bugs/679/.

The returned datatype for a SQLServer Date type is returned as a varchar with a length of 10. This is wrong, it should return as Sql.Date. int iType = rsMeta.getInt("DATA_TYPE"); String tmp = rsMeta.getString("TYPE_NAME");

Answer 2

This still appears to be an open issue with jTDS 1.3.1. I was able to work around it by querying the SQL Server table catalog directly for the tables I'm working with, and getting a list of date columns for the table:

private HashMap<String,Boolean> getDateColumns (String tableName, String schemaName, Connection conn) throws Exception {
    String sql = "SELECT table_name + ',' + column_name" 
                + " FROM  INFORMATION_SCHEMA.COLUMNS " 
                + " WHERE TABLE_SCHEMA = N'" + schemaName + "' "
                + " AND   table_name = N'" + tableName + "' " 
                + " AND data_type IN ('date', 'datetime', 'datetime2')";

    Statement stmt = conn.createStatement();                        
    ResultSet rs = stmt.executeQuery(sql);
    HashMap<String,Boolean> dateCols = new HashMap<String,Boolean>();

    while (rs.next()) {
        String tableColKey = rs.getString(1);           
        dateCols.put(tableColKey.toUpperCase(), true );
    }

    rs.close();     
    return dateCols;        
}

Once you have this list, you can explicitly check and see if the column is a date type:

private ResultSetMetaData getTableMetaData (String tableName, Connection conn) throws Exception {
    String sql = "SELECT * FROM dbo." + tableName + " where 1 = 2 ";
    Statement stmt = conn.createStatement();                        
    ResultSet rs = stmt.executeQuery(sql);
    ResultSetMetaData rsmd = rs.getMetaData();
    rs.close();

    HashMap<String,Boolean> dateColumns =  getDateColumns (tableName, conn); 

    for (int i = 1; i <= rsmd.getColumnCount(); i++) {                

        String key = tableName + "," + rsmd.getColumnName(i);
        int type = -1;
        if (dateColumns.containsKey(key)) {
            type = Types.DATE;
        }
        else {
            type = rsmd.getColumnType(i);
        }

        System.out.println ("... col: " + rsmd.getColumnName(i) + ", driver type name: " + rsmd.getColumnTypeName(i) + ", driver type: " + rsmd.getColumnType(i) + ", final data type: " + type);
    }       

    return rsmd;
}

So, say I have a sample table with three columns:

SAMPLE
------------------
SITE_ID     numeric
START_DATE  date
END_DATE    date

This code will print the following values when run with jTDS:

... col: SITE_ID, driver type name: numeric, driver type: 2, final data type: 2
... col: START_DATE, driver type name: nvarchar, driver type: 12, final data type: 91
... col: END_DATE, driver type name: nvarchar, driver type: 12, final data type: 91

It's not ideal, but it should work for others with a similar problem.