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- JDBC: CallableStatement
A
java.sql.CallableStatement
is used to call stored procedures in a database.
A stored procedure is like a function or method in a class, except it lives inside the database. Some database heavy operations may benefit performance-wise from being executed inside the same memory space as the database server, as a stored procedure.
Creating a CallableStatement
You create an instance of a
CallableStatement
by calling the prepareCall()
method on a connection object. Here is an example:CallableStatement callableStatement = connection.prepareCall("{call calculateStatistics(?, ?)}");
If the stored procedure returns a
ResultSet
, and you need a non-default ResultSet
(e.g. with different holdability, concurrency etc. characteristics), you will need to specify these characteristics already when creating the CallableStatement
. Here is an example:CallableStatement callableStatement = connection.prepareCall("{call calculateStatistics(?, ?)}", ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY, ResultSet.CLOSE_CURSORS_OVER_COMMIT );
Setting Parameter Values
Once created, a
CallableStatement
is very similar to a PreparedStatement
. For instance, you can set parameters into the SQL, at the places where you put a ? . Here is an example:CallableStatement callableStatement = connection.prepareCall("{call calculateStatistics(?, ?)}"); callableStatement.setString(1, "param1"); callableStatement.setInt (2, 123);
Executing the CallableStatement
Once you have set the parameter values you need to set, you are ready to execute the
CallableStatement
. Here is how that is done:ResultSet result = callableStatement.executeQuery();
The
executeQuery()
method is used if the stored procedure returns a ResultSet
.
If the stored procedure just updates the database, you can call the
executeUpdate()
method instead, like this:callableStatement.executeUpdate();
Batch Updates
You can group multiple calls to a stored procedure into a batch update. Here is how that is done:
CallableStatement callableStatement = connection.prepareCall("{call calculateStatistics(?, ?)}"); callableStatement.setString(1, "param1"); callableStatement.setInt (2, 123); callableStatement.addBatch(); callableStatement.setString(1, "param2"); callableStatement.setInt (2, 456); callableStatement.addBatch(); int[] updateCounts = callableStatement.executeBatch();
OUT Parameters
A stored procedure may return
OUT
parameters. That is, values that are returned instead of, or in addition to, a ResultSet
. After executing the CallableStatement
you can then access these OUT
parameters from the CallableStatement
object. Here is an example:CallableStatement callableStatement = connection.prepareCall("{call calculateStatistics(?, ?)}"); callableStatement.setString(1, "param1"); callableStatement.setInt (2, 123); callableStatement.registerOutParameter(1, java.sql.Types.VARCHAR); callableStatement.registerOutParameter(2, java.sql.Types.INTEGER); ResultSet result = callableStatement.executeQuery(); while(result.next()) { ... } String out1 = callableStatement.getString(1); int out2 = callableStatement.getInt (2);
It is recommended that you first process the
ResultSet
before trying to access any OUT
parameters. This is recommended for database compatibility reasons.