用JDBC如何调用存储过程

Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql:///test";
Connection cn = DriverManager.getConnection(url, "root", "root");
String sql = "{call insert_student(?,?,?)}";
CallableStatement cstmt = cn.prepareCall(sql);
cstmt.registerOutParameter(3, Types.INTEGER);
cstmt.setString(1, "wangwu");
cstmt.setInt(2, 25);
cstmt.execute();
// get第几个，不同的数据库不一样，建议不写
System.out.println(cstmt.getString(3));