Java Reference
In-Depth Information
When a
ResultSet
is returned from
executeQuery()
, it is positioned at the first record
that has been retrieved. The following methods of
ResultSet
can be used to pull infor-
mation from the current record:
getDate(
String
)
—Returns the
Date
value stored in the specified field name
(using the
Date
class in the
java.sql
package, not
java.util.Date
)
n
getDouble(
String
)
—Returns the
double
value stored in the specified field name
n
getFloat(
String
)
—Returns the
float
value stored in the specified field name
n
getInt(
String
)
—Returns the
int
value stored in the specified field name
n
getLong(
String
)
—Returns the
long
value stored in the specified field name
n
getString(
String
)
—Returns the
String
stored in the specified field name
n
These are just the simplest methods available in the
ResultSet
interface. The methods
you should use depend on the form that the field data takes in the database, although
methods such as
getString()
and
getInt()
can be more flexible in the information they
retrieve from a record.
You also can use an integer as the argument to any of these methods, such as
getString(5)
, instead of a string. The integer indicates which field to retrieve (1 for the
first field, 2 for the second field, and so on).
18
An
SQLException
is thrown if a database error occurs as you try to retrieve information
from a resultset. You can call this exception's
getSQLState()
and
getErrorCode()
methods to learn more about the error.
After you have pulled the information you need from a record, you can move to the next
record by calling the
next()
method of the
ResultSet
object. This method returns a
false
Boolean value when it tries to move past the end of a resultset.
Normally, you can move through a resultset once from start to finish, after which you
can't retrieve its contents again.
When you're finished using a connection to a data source, you can close it by calling the
connection's
close()
method with no arguments.
Listing 18.1 contains the
CoalReporter
application, which uses the JDBC-ODBC bridge
and an SQL statement to retrieve some records from an energy database. Four fields are
retrieved from each record indicated by the SQL statement:
FIPS
,
Country
,
Year
, and
Anthracite Production
. The resultset is sorted according to the
Year
field, and these
fields are displayed to standard output.
