MYSQL存储过程未返回java中的结果集

DELIMITER //

CREATE PROCEDURE get_users(OUT user_list TEXT)
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE user_name VARCHAR(255);
    DECLARE cur CURSOR FOR SELECT name FROM users;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    SET user_list = '';

    OPEN cur;

    read_loop: LOOP
        FETCH cur INTO user_name;
        IF done THEN
            LEAVE read_loop;
        END IF;
        SET user_list = CONCAT(user_list, user_name, ',');
    END LOOP;

    CLOSE cur;

    -- Remove the trailing comma
    SET user_list = LEFT(user_list, LENGTH(user_list) - 1);
END //

DELIMITER ;

import java.sql.*;

public class Main {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String user = "username";
        String password = "password";

        try (Connection conn = DriverManager.getConnection(url, user, password)) {
            CallableStatement stmt = conn.prepareCall("{call get_users(?)}");
            stmt.registerOutParameter(1, Types.VARCHAR);
            stmt.execute();

            String userList = stmt.getString(1);
            System.out.println("Users: " + userList);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}