NOTE: Above stored procedure has been written
for Oracle, but we are working with MySQL database so let us write same stored
procedure for MySQL as follows to create it in EMP database:
DELIMITER $$
DROP PROCEDURE IF EXISTS `EMP`.`getEmpName` $$
CREATE PROCEDURE `EMP`.`getEmpName`
(IN EMP_ID INT, OUT EMP_FIRST VARCHAR(255))
BEGIN
SELECT first INTO EMP_FIRST
FROM Employees
WHERE ID = EMP_ID;
END $$
DELIMITER ;
Three types of parameters exist: IN, OUT, and INOUT.
The PreparedStatement object only uses the IN parameter. The CallableStatement
object can use all three.
Here are the definitions of each:
|
Parameter
|
Description
|
|
IN
|
A parameter whose
value is unknown when the SQL statement is created. You bind values to IN
parameters with the setXXX() methods.
|
|
OUT
|
A parameter whose
value is supplied by the SQL statement it returns. You retrieve values from
theOUT parameters with the getXXX() methods.
|
|
INOUT
|
A parameter that
provides both input and output values. You bind variables with the setXXX()
methods and retrieve values with the getXXX() methods.
|
The following code snippet shows how to employ the Connection.prepareCall()
method to instantiate a CallableStatement object based on the preceding
stored procedure:
CallableStatement cstmt = null;
try {
String SQL = "{call getEmpName (?, ?)}";
cstmt = conn.prepareCall (SQL);
. . .
}
catch (SQLException e) {
. . .
}
finally {
. . .
}
The String variable SQL represents the stored
procedure, with parameter placeholders.
Using CallableStatement objects is much like using
PreparedStatement objects. You must bind values to all parameters before
executing the statement, or you will receive an SQLException.
If you have IN parameters, just follow the same rules
and techniques that apply to a PreparedStatement object; use the setXXX()
method that corresponds to the Java data type you are binding.
When you use OUT and INOUT parameters you must employ
an additional CallableStatement method, registerOutParameter(). The
registerOutParameter() method binds the JDBC data type to the data type the
stored procedure is expected to return.
Once you call your stored procedure, you retrieve the
value from the OUT parameter with the appropriate getXXX() method. This method
casts the retrieved value of SQL type to a Java data type.
Closing
CallableStatement Obeject:
Just as you close other Statement object, for the same
reason you should also close the CallableStatement object.
A simple call to the close() method will do the job. If
you close the Connection object first it will close the CallableStatement
object as well. However, you should always explicitly close the
CallableStatement object to ensure proper cleanup.
CallableStatement cstmt = null;
try {
String SQL = "{call getEmpName (?, ?)}";
cstmt = conn.prepareCall (SQL);
. . .
}
catch (SQLException e) {
. . .
}
finally {
cstmt.close();
}
Tags:
Advanced Java