Java Reference
In-Depth Information
The user can then view different entries by pressing the
Previous
JButton
or
Next
JButton
, which results in calls to methods
previousButtonActionPerformed
(lines 241-
250) or
nextButtonActionPerformed
(lines 253-262), respectively. Alternatively, the
user can enter a number in the
indexTextField
and press
Enter
to view a particular entry.
This results in a call to method
indexTextFieldActionPerformed
(lines 290-306) to dis-
play the specified record.
Many database management systems can store individual or sets of SQL statements in a
database, so that programs accessing that database can invoke them. Such named collec-
tions of SQL statements are called
stored procedures
. JDBC enables programs to invoke
stored procedures using objects that implement the interface
CallableStatement
.
CallableStatement
s can receive arguments specified with the methods inherited from in-
terface
PreparedStatement
. In addition,
CallableStatement
s can specify
output param-
eters
in which a stored procedure can place return values. Interface
CallableStatement
includes methods to specify which parameters in a stored procedure are output parameters.
The interface also includes methods to obtain the values of output parameters returned
from a stored procedure.
Portability Tip 24.6
Although the syntax for creating stored procedures differs across database management sys-
tems, the interface
CallableStatement
provides a uniform interface for specifying input
and output parameters for stored procedures and for invoking stored procedures.
Portability Tip 24.7
According to the Java API documentation for interface
CallableStatement
, for maxi-
mum portability between database systems, programs should process the update counts
(which indicate how many rows were updated) or
ResultSet
s returned from a
Call-
ableStatement
before obtaining the values of any output parameters.
Many database applications require guarantees that a series of database insertions, updates
and deletions executes properly before the application continues processing the next data-
base operation. For example, when you transfer money electronically between bank ac-
counts, several factors determine if the transaction is successful. You begin by specifying
the source account and the amount you wish to transfer from that account to a destination
account. Next, you specify the destination account. The bank checks the source account
to determine whether its funds are sufficient to complete the transfer. If so, the bank with-
draws the specified amount and, if all goes well, deposits it into the destination account to
complete the transfer. What happens if the transfer fails after the bank withdraws the mon-
ey from the source account? In a proper banking system, the bank redeposits the money
in the source account. How would you feel if the money was subtracted from your source
account and the bank
did not
deposit the money in the destination account?
Transaction processing
enables a program that interacts with a database to
treat a
database operation (or set of operations) as a single operation
. Such an operation also is known
