Applying Strategy, Factory Method, and Builder Patterns in Spring for Reward Distribution

Design patterns, when applied correctly, make code simpler and more extensible; this article demonstrates how to use the Strategy, Factory Method, and Builder patterns in Spring through a reward‑distribution example.

1. Strategy Pattern – The pattern is illustrated by defining a PrizeSender interface with support() and sendPrize() methods, then providing three concrete implementations ( PointSender , VirtualCurrencySender , CashSender ) that handle different prize types.

public interface PrizeSender {
/** 判断当前实例是否支持当前奖励的发放 */
boolean support(SendPrizeRequest request);
/** 发放奖励 */
void sendPrize(SendPrizeRequest request);
}

// 积分发放
@Component
public class PointSender implements PrizeSender {
@Override
public boolean support(SendPrizeRequest request) {
return request.getPrizeType() == PrizeTypeEnum.POINT;
}
@Override
public void sendPrize(SendPrizeRequest request) {
System.out.println("发放积分");
}
}

// 虚拟币发放
@Component
public class VirtualCurrencySender implements PrizeSender {
@Override
public boolean support(SendPrizeRequest request) {
return PrizeTypeEnum.VIRTUAL_CURRENCY == request.getPrizeType();
}
@Override
public void sendPrize(SendPrizeRequest request) {
System.out.println("发放虚拟币");
}
}

// 现金发放
@Component
public class CashSender implements PrizeSender {
@Override
public boolean support(SendPrizeRequest request) {
return PrizeTypeEnum.CASH == request.getPrizeType();
}
@Override
public void sendPrize(SendPrizeRequest request) {
System.out.println("发放现金");
}
}

Key points: annotate implementations with @Component , provide a boolean support() method to decide applicability, keep business logic in sendPrize() , and pass a request object rather than primitive parameters to allow future extensions.

2. Factory Method Pattern – A factory class selects the appropriate PrizeSender based on the request. The factory iterates over all beans of type PrizeSender injected by Spring and returns the first that supports the request.

@Component
public class PrizeSenderFactory {
@Autowired
private List<PrizeSender> prizeSenders;
public PrizeSender getPrizeSender(SendPrizeRequest request) {
for (PrizeSender prizeSender : prizeSenders) {
if (prizeSender.support(request)) {
return prizeSender;
}
}
throw new UnsupportedOperationException("unsupported request: " + request);
}
}

The client obtains a PrizeSender from the factory and calls sendPrize() , decoupling the caller from concrete implementations. Adding a new prize type only requires a new PrizeSender bean.

@Service
public class ApplicationService {
@Autowired
private PrizeSenderFactory prizeSenderFactory;
public void mockedClient() {
SendPrizeRequest request = new SendPrizeRequest();
request.setPrizeType(PrizeTypeEnum.POINT);
PrizeSender prizeSender = prizeSenderFactory.getPrizeSender(request);
prizeSender.sendPrize(request);
}
}

3. Builder Pattern – The article shows a Spring‑managed builder for constructing SendPrizeRequest . The inner static Builder class is annotated with @Component and @Scope("prototype") so each request gets a fresh builder instance that can have state.

public class SendPrizeRequest {
private final PrizeTypeEnum prizeType;
private final int amount;
private final String userId;
public SendPrizeRequest(PrizeTypeEnum prizeType, int amount, String userId) {
this.prizeType = prizeType;
this.amount = amount;
this.userId = userId;
}
@Component
@Scope("prototype")
public static class Builder {
@Autowired
PrizeService prizeService;
private int prizeId;
private String userId;
public Builder prizeId(int prizeId) {
this.prizeId = prizeId;
return this;
}
public Builder userId(String userId) {
this.userId = userId;
return this;
}
public SendPrizeRequest build() {
Prize prize = prizeService.findById(prizeId);
return new SendPrizeRequest(prize.getPrizeType(), prize.getAmount(), userId);
}
}
// getters omitted
}

The builder is obtained from the Spring ApplicationContext to ensure a new prototype instance each time.

@Service
public class ApplicationService {
@Autowired
private PrizeSenderFactory prizeSenderFactory;
@Autowired
private ApplicationContext context;
public void mockedClient() {
SendPrizeRequest request = newPrizeSendRequestBuilder()
.prizeId(1)
.userId("u4352234")
.build();
PrizeSender prizeSender = prizeSenderFactory.getPrizeSender(request);
prizeSender.sendPrize(request);
}
public Builder newPrizeSendRequestBuilder() {
return context.getBean(Builder.class);
}
}

The article concludes that using these three patterns together yields a clean, extensible reward‑distribution module where new prize types can be added without modifying existing business logic.