前言

Java 8 函数式编程可以简化传统设计模式使用方式，下面看两个重构例子，用Functional Interface 实现策略工厂。

案例一

• 原始实现：

switch (agreementBuildItem.getSignNaturalType()) {
            case LEGAL_PERSON:
                party = newParty(company.getLegalPerson());
                break;
            case LEGAL_PERSON_SPOUSE:
                party = newParty(company.getLegalPerson().getSpouse());
                break;
            case ACTUAL_CONTROLLER:
                party = newParty(company.getActualController());
                break;
            case ACTUAL_CONTROLLER_SPOUSE:
                party = newParty(company.getActualController().getSpouse());
                break;
            case LEGAL_PERSON_ALIPAY_ACCOUNT:
                party = newParty(company.getLegalPerson().getAlipayAccountData());
                break;
            case ACTUAL_CONTROLLER_ALIPAY_ACCOUNT:
                party = newParty(company.getActualController().getAlipayAccountData());
                break;
            case COMPANY_TRADE_ALIPAY_ACCOUNT:
                party = newParty(company.getAlipayAccountMap().get("TRADE_ALIPAY_ACCOUNT"));
                break;
            default:
                throw new UnsupportedOperationException();
        }

• 重构后实现:

/**
 * @author zhengyu.nie
 * 2020/11/24.
 */
public final class PartyFactory {
    private PartyFactory() {}

    private static final Function<Company, Optional<Party>> LEGAL_PERSON_PARTY_FUNC = company
        -> newParty(company.getLegalPerson());

    private static final Function<Company, Optional<Party>> LEGAL_PERSON_SPOUSE_PARTY_FUNC = company
        -> newParty(company.getLegalPerson().getSpouse());

    private static final Function<Company, Optional<Party>> ACTUAL_CONTROLLER_PARTY_FUNC = company
        -> newParty(company.getActualController());

    private static final Function<Company, Optional<Party>> ACTUAL_CONTROLLER_SPOUSE_PARTY_FUNC = company
        -> newParty(company.getActualController().getSpouse());

    private static final Function<Company, Optional<Party>> LEGAL_PERSON_ALIPAY_PARTY_FUNC = company
        -> newParty(company.getLegalPerson().getAlipayAccountData());

    private static final Function<Company, Optional<Party>> ACTUAL_CONTROLLER_ALIPAY_PARTY_FUNC = company
        -> newParty(company.getActualController().getAlipayAccountData());

    private static final Function<Company, Optional<Party>> COMPANY_TRADE_ALIPAY_ACCOUNT_PARTY_FUNC = company
        -> newParty(company.getAlipayAccountMap().get("TRADE_ALIPAY_ACCOUNT"));

    private static final Map<SignNaturalType, Function<Company, Optional<Party>>> PARTY_FUNC_MAP = Maps.newHashMap();

    static {
        PARTY_FUNC_MAP.put(SignNaturalType.LEGAL_PERSON, LEGAL_PERSON_PARTY_FUNC);
        PARTY_FUNC_MAP.put(SignNaturalType.LEGAL_PERSON_SPOUSE, LEGAL_PERSON_SPOUSE_PARTY_FUNC);
        PARTY_FUNC_MAP.put(SignNaturalType.ACTUAL_CONTROLLER, ACTUAL_CONTROLLER_PARTY_FUNC);
        PARTY_FUNC_MAP.put(SignNaturalType.ACTUAL_CONTROLLER_SPOUSE, ACTUAL_CONTROLLER_SPOUSE_PARTY_FUNC);
        PARTY_FUNC_MAP.put(SignNaturalType.LEGAL_PERSON_ALIPAY_ACCOUNT, LEGAL_PERSON_ALIPAY_PARTY_FUNC);
        PARTY_FUNC_MAP.put(SignNaturalType.ACTUAL_CONTROLLER_ALIPAY_ACCOUNT, ACTUAL_CONTROLLER_ALIPAY_PARTY_FUNC);
        PARTY_FUNC_MAP.put(SignNaturalType.COMPANY_TRADE_ALIPAY_ACCOUNT, COMPANY_TRADE_ALIPAY_ACCOUNT_PARTY_FUNC);
    }

    public static Optional<Party> getParty(Company company, SignNaturalType signNaturalType) {
        Function<Company, Optional<Party>> companyOptionalFunction = PARTY_FUNC_MAP.get(signNaturalType);

        if (companyOptionalFunction == null) {
            throw new UnsupportedOperationException();
        }

        Optional<Party> party = companyOptionalFunction.apply(company);

        return party;
    }
}

案例二

• 原始实现

  public CreditSchema convertToCreditSchema(CreditSchemaDTO creditSchemaDto) {
        CreditSchemaBuilder creditSchemaBuilder = CreditSchema.builder();
        creditSchemaBuilder.creditNo(creditSchemaDto.getCreditNo());
        creditSchemaBuilder.fgNo(creditSchemaDto.getFgNo());
        creditSchemaBuilder.institutionCreditNo(creditSchemaDto.getInstitutionCreditNo());
        creditSchemaBuilder.institutionCreditQuotaNo(creditSchemaDto.getInstitutionCreditQuotaNo());
        creditSchemaBuilder.riskCreditNo(creditSchemaDto.getRiskCreditNo());


        creditSchemaDto.getFactors().forEach(factor -> {
                if (factor instanceof RepaymentDayFactor) {
                    RepaymentDayFactor repaymentDayFactor = (RepaymentDayFactor)factor;
                    creditSchemaBuilder.repaymentDay(repaymentDayFactor.getRepaymentDay());
                }
                if (factor instanceof RepaymentMethodFactor) {
                    RepaymentMethodFactor repaymentMethodFactor = (RepaymentMethodFactor)factor;
                    creditSchemaBuilder.repaymentMethod(repaymentMethodFactor.getValue().name());
                }
                if (factor instanceof InterestRateFactor) {
                    InterestRateFactor interestRateFactor = (InterestRateFactor)factor;
                    creditSchemaBuilder.interestRate(interestRateFactor.getValue());
                }
                ………………
            }
        );

        return creditSchemaBuilder.build();
    }

• 重构后实现

    public CreditSchema convertToCreditSchema(CreditSchemaDTO creditSchemaDto) {
        CreditSchemaBuilder creditSchemaBuilder = CreditSchema.builder();
        creditSchemaBuilder.creditNo(creditSchemaDto.getCreditNo());
        creditSchemaBuilder.fgNo(creditSchemaDto.getFgNo());
        creditSchemaBuilder.institutionCreditNo(creditSchemaDto.getInstitutionCreditNo());
        creditSchemaBuilder.institutionCreditQuotaNo(creditSchemaDto.getInstitutionCreditQuotaNo());

        creditSchemaDto.getFactors().forEach(factor -> creditResultFactorAccessor.access(creditSchemaBuilder, factor));

        return creditSchemaBuilder.build();
    }

/**
 * @author zhengyu.nie
 * 2020/11/9.
 */
@Component
class CreditResultFactorAccessor {

    private static final BiConsumer<CreditSchemaBuilder, RepaymentMethodFactor> CREDIT_SCHEMA_FACTOR
        = (creditSchemaBuilder, repaymentMethodFactor) ->
        creditSchemaBuilder.repaymentMethod(String.valueOf(repaymentMethodFactor.getValue()));

    private static final BiConsumer<CreditSchemaBuilder, InterestRateFactor> INTEREST_RATE_FACTOR
        = (creditSchemaBuilder, interestRateFactor) -> {
        creditSchemaBuilder.interestUnit(String.valueOf(interestRateFactor.getUnit()));
        creditSchemaBuilder.interestRate(interestRateFactor.getValue());
    };

    private static final BiConsumer<CreditSchemaBuilder, LoanTermFactor> CREDIT_SCHEMA_LOAN_TERM_FACTOR
        = (creditSchemaBuilder, loanTermFactor) -> {
        creditSchemaBuilder.loanTermUnit(String.valueOf(loanTermFactor.getUnit()));
        creditSchemaBuilder.loanTerm(loanTermFactor.getValue());
    };

    private static final BiConsumer<CreditSchemaBuilder, ExpirationFactor> CREDIT_SCHEMA_EXPIRATION_FACTOR
        = (creditSchemaBuilder, expirationFactor) -> {
        creditSchemaBuilder.creditStartTime(expirationFactor.getStartTime());
        creditSchemaBuilder.creditEndTime(expirationFactor.getEndTime());
    };

    private static final BiConsumer<CreditSchemaBuilder, RepaymentDayFactor> LOAN_SCHEMA_REPAYMENT_DAY_FACTOR
        = (creditSchemaBuilder, repaymentDayFactor) -> creditSchemaBuilder.repaymentDay(
        repaymentDayFactor.getRepaymentDay());

    private static final Map<FactorTypeEnum, BiConsumer> consumerMap = new HashMap<>();

    static {
        consumerMap.put(FactorTypeEnum.REPAYMENT_METHOD, CREDIT_SCHEMA_FACTOR);
        consumerMap.put(FactorTypeEnum.INTEREST_RATE, INTEREST_RATE_FACTOR);
        consumerMap.put(FactorTypeEnum.LOAN_TERM, CREDIT_SCHEMA_LOAN_TERM_FACTOR);
        consumerMap.put(FactorTypeEnum.REPAYMENT_DAY, LOAN_SCHEMA_REPAYMENT_DAY_FACTOR);
        consumerMap.put(FactorTypeEnum.EXPIRATION_DATE, CREDIT_SCHEMA_EXPIRATION_FACTOR);
    }

    public void access(CreditSchemaBuilder creditSchemaBuilder, Factor factor) {
        if (consumerMap.containsKey(factor.getFactorType())) {
            consumerMap.get(factor.getFactorType()).accept(creditSchemaBuilder, factor);
        }
    }

}