MySQL Connector/J 8.0 Developer Guide
Connector/J fully implements the
java.sql.CallableStatement
interface.
For more information on MySQL stored procedures, please refer to Using Stored Routines.
Connector/J exposes stored procedure functionality through
JDBC's CallableStatement
interface.
The following example shows a stored procedure that returns the
value of inOutParam
incremented by 1, and the
string passed in using inputParam
as a
ResultSet
:
Example 7.3 Connector/J: Calling Stored Procedures
CREATE PROCEDURE demoSp(IN inputParam VARCHAR(255), \ INOUT inOutParam INT) BEGIN DECLARE z INT; SET z = inOutParam + 1; SET inOutParam = z; SELECT inputParam; SELECT CONCAT('zyxw', inputParam); END
To use the demoSp
procedure with Connector/J,
follow these steps:
Prepare the callable statement by using
Connection.prepareCall()
.
Notice that you have to use JDBC escape syntax, and that the parentheses surrounding the parameter placeholders are not optional:
Example 7.4 Connector/J: Using Connection.prepareCall()
import java.sql.CallableStatement; ... // // Prepare a call to the stored procedure 'demoSp' // with two parameters // // Notice the use of JDBC-escape syntax ({call ...}) // CallableStatement cStmt = conn.prepareCall("{call demoSp(?, ?)}"); cStmt.setString(1, "abcdefg");
Connection.prepareCall()
is an
expensive method, due to the metadata retrieval that the
driver performs to support output parameters. For
performance reasons, minimize unnecessary calls to
Connection.prepareCall()
by reusing
CallableStatement
instances in your
code.
Register the output parameters (if any exist)
To retrieve the values of output parameters (parameters
specified as OUT
or
INOUT
when you created the stored
procedure), JDBC requires that they be specified before
statement execution using the various
registerOutputParameter()
methods in
the CallableStatement
interface:
Example 7.5 Connector/J: Registering output parameters
import java.sql.Types; ... // // Connector/J supports both named and indexed // output parameters. You can register output // parameters using either method, as well // as retrieve output parameters using either // method, regardless of what method was // used to register them. // // The following examples show how to use // the various methods of registering // output parameters (you should of course // use only one registration per parameter). // // // Registers the second parameter as output, and // uses the type 'INTEGER' for values returned from // getObject() // cStmt.registerOutParameter(2, Types.INTEGER); // // Registers the named parameter 'inOutParam', and // uses the type 'INTEGER' for values returned from // getObject() // cStmt.registerOutParameter("inOutParam", Types.INTEGER); ...
Set the input parameters (if any exist)
Input and in/out parameters are set as for
PreparedStatement
objects. However,
CallableStatement
also supports
setting parameters by name:
Example 7.6 Connector/J: Setting CallableStatement
input
parameters
... // // Set a parameter by index // cStmt.setString(1, "abcdefg"); // // Alternatively, set a parameter using // the parameter name // cStmt.setString("inputParam", "abcdefg"); // // Set the 'in/out' parameter using an index // cStmt.setInt(2, 1); // // Alternatively, set the 'in/out' parameter // by name // cStmt.setInt("inOutParam", 1); ...
Execute the CallableStatement
, and
retrieve any result sets or output parameters.
Although CallableStatement
supports
calling any of the Statement
execute
methods (executeUpdate()
,
executeQuery()
or
execute()
), the most flexible method to
call is execute()
, as you do not need
to know ahead of time if the stored procedure returns result
sets:
Example 7.7 Connector/J: Retrieving results and output parameter values
... boolean hadResults = cStmt.execute(); // // Process all returned result sets // while (hadResults) { ResultSet rs = cStmt.getResultSet(); // process result set ... hadResults = cStmt.getMoreResults(); } // // Retrieve output parameters // // Connector/J supports both index-based and // name-based retrieval // int outputValue = cStmt.getInt(2); // index-based outputValue = cStmt.getInt("inOutParam"); // name-based ...