CQRS 패턴

Java code

import java.util.*;

// Command 모델 (쓰기)
interface Command {}
record CreateProductCommand(String name, int price) implements Command {}
record UpdatePriceCommand(String id, int newPrice) implements Command {}

// Query 모델 (읽기)
interface Query {}
record GetProductQuery(String id) implements Query {}
record SearchProductQuery(String keyword) implements Query {}

// 쓰기 모델
class ProductCommandHandler {
    private final Map<String, int[]> writeStore = new HashMap<>();

    String handle(CreateProductCommand cmd) {
        String id = UUID.randomUUID().toString().substring(0, 8);
        writeStore.put(id, new int[]{cmd.price()});
        System.out.println("생성: " + id);
        return id;
    }

    void handle(UpdatePriceCommand cmd) {
        writeStore.get(cmd.id())[0] = cmd.newPrice();
        System.out.println("가격 변경: " + cmd.id());
    }
}

// 읽기 모델 (비정규화된 뷰)
record ProductView(String id, String name, int price) {}

class ProductQueryHandler {
    private final Map<String, ProductView> readStore = new HashMap<>();

    void sync(String id, String name, int price) {
        readStore.put(id, new ProductView(id, name, price));
    }

    ProductView handle(GetProductQuery query) {
        return readStore.get(query.id());
    }

    List<ProductView> handle(SearchProductQuery query) {
        return readStore.values().stream()
            .filter(p -> p.name().contains(query.keyword()))
            .toList();
    }
}