Java 存储过程返回空值

我有一个返回用户名的存储过程。我正在从java（EclipseIDE）调用存储过程。存储过程返回的值为Null。如何避免此

Null

值。
这是我的存储过程

USE `employee`;
DROP procedure IF EXISTS `add1`;
DELIMITER $$
USE `employee`$$
CREATE DEFINER=`root`@`localhost` PROCEDURE `add1`(IN UserId int,
                                                   IN UserFirstName varchar(50),
                                                   IN UserLastName varchar(50),
                                                   IN Education varchar(50),
                                                   IN MarksInME int,
                                                   IN MarksInBE int,
                                                   IN MarksInPUC int,
                                                   IN Gender varchar(50),
                                                   OUT UserName varchar(50))
  BEGIN
    declare varName varchar(50);
    select UserFirstName into varName from User where UserId=3516;
    set UserName=varName;
    insert into   user(UserId,UserFirstName,UserLastName,Education,MarksInME,MarksInBE,MarksInPUC,Gender)
    values(UserId,UserFirstName,UserLastName,Education,MarksInME,MarksInBE, MarksInPUC,Gender);

  END$$
DELIMITER ;

我正在调用存储过程：

    java.sql.CallableStatement cStmt = conn.prepareCall("{call add1(?,?,?,?,?,?,?,?,?)}");
    cStmt.setInt(1,3541);    
    cStmt.setString(2,"pALLAVI"); 
    cStmt.setString(3,"K"); 
    cStmt.setString(4,"BE"); 
    cStmt.setInt(5,0);  
    cStmt.setInt(6,60); 
    cStmt.setInt(7,600);  
    cStmt.setString(8,"chetana@gmail.com"); 
    cStmt.registerOutParameter(9, java.sql.Types.VARCHAR);
    cStmt.execute();
    userName = cStmt.getString(9);

当我尝试打印用户名时，其打印为空？

用户ID是硬编码的：

select UserFirstName into varName from User where UserId=3516;

请检查以下查询：

call add1(3541,'pALLAVI','K','BE',0,60,600,'chetana@gmail.com',@UserName);
SELECT @UserName;