组合器模式

Question

我对“组合器”模式得到的结果有个小问题。

public interface CustomerRegistrationValidator 
    extends Function<Customer, ValidationResult> {

    static CustomerRegistrationValidator isEmailValid() {
        return customer -> customer.getEmail().contains("@") ? 
                    ValidationResult.SUCCESS : ValidationResult.EMAIL_NOT_VALID;
    }

    static CustomerRegistrationValidator isPhoneNumberValid() {
        return customer -> customer.getPhoneNumber().startsWith("+0") ?  
                    ValidationResult.SUCCESS : ValidationResult.PHONE_NUMBER_NOT_VALID;
    }

    static CustomerRegistrationValidator isAnAdult() {
        return customer -> Period.between(customer.getDob(), LocalDate.now()).getYears() > 16 ?  
                    ValidationResult.SUCCESS : ValidationResult.IS_NOT_AN_ADULT;
    }

    default CustomerRegistrationValidator and (CustomerRegistrationValidator other) {
        return customer -> {
            ValidationResult result = this.apply(customer);

            return result.equals(ValidationResult.SUCCESS) ? other.apply(customer) : result;
        };
    }

    enum ValidationResult {
        SUCCESS,
        PHONE_NUMBER_NOT_VALID,
        EMAIL_NOT_VALID,
        IS_NOT_AN_ADULT
    }

}

public class Main {
    public static void main(String[] args) {

            Customer customer = new Customer(
                    "Alice", 
                    "alicegmail.com", 
                    "089877878", 
                    LocalDate.of(2000, 1, 1)
            );

            ValidationResult result = CustomerRegistrationValidator.isEmailValid()
                .and(CustomerRegistrationValidator.isPhoneNumberValid())
                .and(CustomerRegistrationValidator.isAnAdult())
                .apply(customer);

            System.out.println(result);

            if (result != ValidationResult.SUCCESS) {
                throw new IllegalStateException(result.name());
            }           
    }
}

假设那些方法(isAnAdult，isEmailValid)中有两个错误，那么它是否只打印了枚举类型中的一个错误，在我的例子中，“EMAIL_NOT_VALID”是例外，而不是两个，而第二个错误指的是'IS_NOT_AN_ADULT‘？

Answer 1

如果希望验证器能够返回多个不同的结果代码(枚举)，则需要将返回类型更改为Set<ValidationResult>，或者更具体地说，更改为EnumSet。

例如，类似这样的事情：

interface CustomerRegistrationValidator
    extends Function<Customer, EnumSet<ValidationResult>> {

    static final EnumSet<ValidationResult> SUCCESS_ONLY = EnumSet.of(ValidationResult.SUCCESS);

    static CustomerRegistrationValidator isEmailValid() {
        return customer -> customer.getEmail().contains("@") ? 
                    SUCCESS_ONLY : EnumSet.of(ValidationResult.EMAIL_NOT_VALID);
    }

    static CustomerRegistrationValidator isPhoneNumberValid() {
        return customer -> customer.getPhoneNumber().startsWith("+0") ?  
                    SUCCESS_ONLY : EnumSet.of(ValidationResult.PHONE_NUMBER_NOT_VALID);
    }

    static CustomerRegistrationValidator isAnAdult() {
        return customer -> Period.between(customer.getDob(), LocalDate.now()).getYears() > 16 ?  
                    SUCCESS_ONLY : EnumSet.of(ValidationResult.IS_NOT_AN_ADULT);
    }

    default CustomerRegistrationValidator and(CustomerRegistrationValidator other) {
        return customer -> {
            EnumSet<ValidationResult> thisResult = this.apply(customer);
            EnumSet<ValidationResult> otherResult = other.apply(customer);
            if (thisResult.equals(SUCCESS_ONLY))
                return otherResult;
            if (otherResult.equals(SUCCESS_ONLY))
                return thisResult;
            EnumSet<ValidationResult> combinedResult = EnumSet.copyOf(thisResult);
            combinedResult.addAll(otherResult);
            return combinedResult;
        };
    }

}