Adapter

使用時機

• 你想要使用一個已經存在的類別（且/或者包含這個類別的子類別），雖然這個類別在功能上符合你的需求， 但是它的介面和你所期待的並不相容。

• 你想要設計可被重複使用的類別，希望這個類別可以跟不相關或是未知的其他類別一起合作。也就是說，
  你希望類別之間既使介面互不相容也可以一起合作。

from: Structural Patterns要解決什麼問題(上)?

from: Adapter Pattern Tutorial with Java Examples

Example

Adaptee

public interface Xpay {

    public String getCreditCardNo();
    public String getCustomerName();
    public String getCardExpMonth();
    public String getCardExpYear();
    public Short getCardCVVNo();
    public Double getAmount();

    public void setCreditCardNo(String creditCardNo);
    public void setCustomerName(String customerName);
    public void setCardExpMonth(String cardExpMonth);
    public void setCardExpYear(String cardExpYear);
    public void setCardCVVNo(Short cardCVVNo);
    public void setAmount(Double amount);

}

public class XpayImpl implements Xpay{

    private String creditCardNo;
    private String customerName;
    private String cardExpMonth;
    private String cardExpYear;
    private Short cardCVVNo;
    private Double amount;

    @Override
    public String getCreditCardNo() {
        return creditCardNo;
    }

    @Override
    public String getCustomerName() {
        return customerName;
    }

    @Override
    public String getCardExpMonth() {
        return cardExpMonth;
    }

    @Override
    public String getCardExpYear() {
        return cardExpYear;
    }

    @Override
    public Short getCardCVVNo() {
        return cardCVVNo;
    }

    @Override
    public Double getAmount() {
        return amount;
    }

    @Override
    public void setCreditCardNo(String creditCardNo) {
        this.creditCardNo = creditCardNo;
    }

    @Override
    public void setCustomerName(String customerName) {
        this.customerName = customerName;
    }

    @Override
    public void setCardExpMonth(String cardExpMonth) {
        this.cardExpMonth = cardExpMonth;
    }

    @Override
    public void setCardExpYear(String cardExpYear) {
        this.cardExpYear = cardExpYear;
    }

    @Override
    public void setCardCVVNo(Short cardCVVNo) {
        this.cardCVVNo = cardCVVNo;
    }

    @Override
    public void setAmount(Double amount) {
        this.amount = amount;
    }

}

Target

public interface PayD {

    public String getCustCardNo();
    public String getCardOwnerName();
    public String getCardExpMonthDate();
    public Integer getCVVNo();
    public Double getTotalAmount();

    public void setCustCardNo(String custCardNo);
    public void setCardOwnerName(String cardOwnerName);
    public void setCardExpMonthDate(String cardExpMonthDate);
    public void setCVVNo(Integer cVVNo);
    public void setTotalAmount(Double totalAmount);
}

Adapter

public class XpayToPayDAdapter implements PayD{

    private String custCardNo;
    private String cardOwnerName;
    private String cardExpMonthDate;
    private Integer cVVNo;
    private Double totalAmount;

    private final Xpay xpay;

    public XpayToPayDAdapter(Xpay xpay){
        this.xpay = xpay;
        setProp();
    }

    @Override
    public String getCustCardNo() {
        return custCardNo;
    }

    @Override
    public String getCardOwnerName() {
        return cardOwnerName;
    }

    @Override
    public String getCardExpMonthDate() {
        return cardExpMonthDate;
    }

    @Override
    public Integer getCVVNo() {
        return cVVNo;
    }

    @Override
    public Double getTotalAmount() {
        return totalAmount;
    }

    @Override
    public void setCustCardNo(String custCardNo) {
        this.custCardNo = custCardNo;
    }

    @Override
    public void setCardOwnerName(String cardOwnerName) {
        this.cardOwnerName = cardOwnerName;
    }

    @Override
    public void setCardExpMonthDate(String cardExpMonthDate) {
        this.cardExpMonthDate = cardExpMonthDate;
    }

    @Override
    public void setCVVNo(Integer cVVNo) {
        this.cVVNo = cVVNo;
    }

    @Override
    public void setTotalAmount(Double totalAmount) {
        this.totalAmount = totalAmount;
    }

    private void setProp(){
        setCardOwnerName(this.xpay.getCustomerName());
        setCustCardNo(this.xpay.getCreditCardNo());
        setCardExpMonthDate(this.xpay.getCardExpMonth()+"/"+this.xpay.getCardExpYear());
        setCVVNo(this.xpay.getCardCVVNo().intValue());
        setTotalAmount(this.xpay.getAmount());
    }

}

Client

public class RunAdapterExample {

    public static void main(String[] args) {

        // Object for Xpay
        Xpay xpay = new XpayImpl();
        xpay.setCreditCardNo("4789565874102365");
        xpay.setCustomerName("Max Warner");
        xpay.setCardExpMonth("09");
        xpay.setCardExpYear("25");
        xpay.setCardCVVNo((short)235);
        xpay.setAmount(2565.23);

        PayD payD = new XpayToPayDAdapter(xpay);
        testPayD(payD);
    }

    private static void testPayD(PayD payD){

        System.out.println(payD.getCardOwnerName());
        System.out.println(payD.getCustCardNo());
        System.out.println(payD.getCardExpMonthDate());
        System.out.println(payD.getCVVNo());
        System.out.println(payD.getTotalAmount());
    }
}

from: Adapter Design Pattern