在Spring bean中實現Null對象設計模式

Question

我使用的是CustomerDTO：

public class CustomerDTO {

    private int customerId;
    private String customerName;
    private String customerAddress;
    public int getCustomerId() {
        return customerId;
    }
    public void setCustomerId(int customerId) {
        this.customerId = customerId;
    }
    public String getCustomerName() {
        return customerName;
    }
    public void setCustomerName(String customerName) {
        this.customerName = customerName;
    }
    public String getCustomerAddress() {
        return customerAddress;
    }
    public void setCustomerAddress(String customerAddress) {
        this.customerAddress = customerAddress;
    }

}

然后我使用CustomerDAO，我根據customerId獲取客戶

public class CustomerDAO {
    private CustomerDTO customer;

    public void setCustomer(CustomerDTO customer) {
        this.customer = customer;
    }

    public CustomerDTO getCustomer(int customerId){
        try{
            if("you get customer based on customer id") then "return the customer";
        }catch(Exception ex){
            return new CustomerDTO();
              //some other work
        }
    }
}

現在這段代碼new CustomerDTO(); 當我嘗試訪問new CustomerDTO().getCustomerName()時，CustomerDAO中的值為null 。 我正在考慮使用默認值初始化字段。

如何使用/不使用Spring框架實現此目的？

Answer 1

嘗試使用Spring

@Value("myValue")
String customerName;

沒有彈簧，只需在聲明中賦值，

 private String customerName="myValue";