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Java Jdbc

1 Java JDBC
2 JDBC Overview
3 JDBC Driver Types
4 JDBC: Database Connections
5 JDBC: Query the Database
6 JDBC: Update the Database
7 JDBC: ResultSet
8 JDBC: PreparedStatement
9 JDBC: Batch Updates
10 JDBC: Transactions
11 JDBC: CallableStatement
12 JDBC: DatabaseMetaData




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.



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