java 调用mysql存储过程

DROP PROCEDURE IF EXISTS `pro_num_user`; 
delimiter ;; 
CREATE PROCEDURE `pro_num_user`(IN user_name varchar(10) ,OUT count_num INT) 
    READS SQL DATA 
BEGIN 
    SELECT COUNT(*) INTO count_num FROM tab_user WHERE 'name'=user_name; 
END 
 ;; 
delimiter ; 

public class Procedure {

    public static final String DRIVER_CLASS = "com.mysql.jdbc.Driver";
    public static final String URL = "jdbc:mysql://127.0.0.1:3306/jpa";
    public static final String USERNAME = "root";
    public static final String PASSWORD = "123456789";

    public static void main(String[] args) throws Exception {
        Class.forName(DRIVER_CLASS);
        Connection connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        String sql = "{CALL pro_num_user(?,?)}"; //调用存储过程
        CallableStatement cstm = connection.prepareCall(sql); //实例化对象cstm
        cstm.setString(1, "name"); //存储过程输入参数
        cstm.registerOutParameter(2, Types.INTEGER); // 设置返回值类型 即返回值
        cstm.execute(); // 执行存储过程
        System.out.println(cstm.getInt(2));
        cstm.close();
        connection.close();
    }
}

create table tab_user (
   id INT NOT NULL AUTO_INCREMENT,
   user_name VARCHAR(100) NOT NULL,
   PRIMARY KEY ( id )
);



DROP PROCEDURE IF EXISTS `pro_num_user`;
delimiter ;;
CREATE PROCEDURE `pro_num_user`(IN _name varchar(10) ,OUT count_num INT)
    READS SQL DATA
BEGIN
    SELECT COUNT(*) INTO count_num FROM tab_user WHERE user_name=_name;
END
 ;;
delimiter ;

IN：参数的值必须在调用存储过程时指定，在存储过程中修改该参数的值不能被返回，为默认值
OUT:该值可在存储过程内部被改变，并可返回
INOUT:调用时指定，并且可被改变和返回