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

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

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

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

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

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

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

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

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

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.