getting voucherPin

I am doin an online credit topup application..and i need a method to fetch and decrypt the voucherpin from Database..

this is my voucher repository Class.

public interface VoucherRepository extends JpaRepository<Voucher, Long>{
    @Query("from voucher v where v.category = :category and v.voucherType = :type and v.denomination = :denomination")
    public String getVoucherPinByCategoryTypeDeno(@Param("category") String category,@Param("voucherType") String type, @Param("denomination") double denomination);
}

this is the voucherService class

public interface VoucherService {

    public String getVoucherPinByCategoryTypeDeno(String category,String type,double denomination);

   //decrypts voucher before being sent.
    public String decryptVoucher();

public void listVoucherTypeImages( String url []);

} this is the implementation

public class VoucherServiceImpl implements VoucherService {

    private VoucherRepository voucherRepository;
    //gets the voucher by category,type and denomination
    @Override
    public String getVoucherPinByCategoryTypeDeno(String category, String type, double denomination) {

        return voucherRepository.getVoucherPinByCategoryTypeDeno(category, type, denomination);
    }

this is my voucherModel Class

@Entity
public class Voucher {

    //declaration of variables with their annotations to map attributes of a voucher
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "voucher_id")
    private Long voucherId;

    @Column(name = "category_id")
    @OneToOne(mappedBy = " Voucher ")
    private VoucherCategory voucherCategory;

    @Column(name = "serial_number")
    private String serialNumber;

    @Column(name = "pin")
    private String pin;

    @Column(name="voucher_type_id")
    @OneToOne
    private VoucherType voucherTypeId;

    @Column(name = "voucher_status_id")
    @OneToOne
    private VoucherStatus statusId;

    @Column(name = "denomination")
    private double denomination;

    @Column(name = "session_lock")
    private Integer sessionLock;

    @Column(name = "updated_by")
    private String updatedBy;

    @Column(name = "expiry_date")
    private String expiryDate;

    @Column(name = "last_modified")
    @Temporal(javax.persistence.TemporalType.DATE)
    private String dateModified;

    @Column(name = "date_entered")
    @Temporal(javax.persistence.TemporalType.DATE)
    private String dateEntered;

    public Long getVoucherId() {
        return voucherId;
    }

    public void setVoucherId(Long voucherId) {
        this.voucherId = voucherId;
    }

    public VoucherCategory getVoucherCategory() {
        return voucherCategory;
    }

    public void setVoucherCategory(VoucherCategory voucherCategory) {
        this.voucherCategory = voucherCategory;
    }

    public String getSerialNumber() {
        return serialNumber;
    }

    public void setSerialNumber(String serialNumber) {
        this.serialNumber = serialNumber;
    }

    public double getDenomination() {
        return denomination;
    }

    public void setDenomination(double denomination) {
        this.denomination = denomination;
    }

    public String getDateEntered() {
        return dateEntered;
    }

    public void setDateEntered(String dateEntered) {
        this.dateEntered = dateEntered;
    }

    public String getExpiryDate() {
        return expiryDate;
    }

    public void setExpiryDate(String expiryDate) {
        this.expiryDate = expiryDate;
    }

    public String getPin() {
        return pin;
    }

    public void setPin(String pin) {
        this.pin = pin;
    }

    public VoucherStatus getStatusId() {
        return statusId;
    }

    public void setStatusId(VoucherStatus statusId) {
        this.statusId = statusId;
    }

    public Integer getSessionLock() {
        return sessionLock;
    }

    public void setSessionLock(Integer sessionLock) {
        this.sessionLock = sessionLock;
    }

    public String getUpdatedBy() {
        return updatedBy;
    }

    public void setUpdatedBy(String updatedBy) {
        this.updatedBy = updatedBy;
    }

    public String getDateModified() {
        return dateModified;
    }

    public void setDateModified(String dateModified) {
        this.dateModified = dateModified;
    }
}