3.6.3 Using JDBC CallableStatements to Execute Stored Procedures

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 3.6 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:

1. 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 3.7 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");

   
   
   Note

   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.

2. 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 3.8 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);
   ...

   
   

3. 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 3.9 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);
   ...

   
   

4. 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 3.10 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
   ...