关于ddd:聊聊cheddar的DomainEvent

序

本文次要钻研一下cheddar的DomainEvent

DomainEvent

Cheddar/cheddar/cheddar-domain/src/main/java/com/clicktravel/cheddar/domain/event/DomainEvent.java

public interface DomainEvent extends Event {

}

DomainEvent接口继承了Event接口

AbstractDomainEvent

Cheddar/cheddar/cheddar-domain/src/main/java/com/clicktravel/cheddar/domain/event/AbstractDomainEvent.java

public abstract class AbstractDomainEvent extends AbstractEvent implements DomainEvent {

    public abstract String context();

    @Override
    public final String type() {
        return context() + "." + getClass().getSimpleName();
    }

}

AbstractDomainEvent继承了AbstractEvent，申明实现了DomainEvent接口，它申明了一个形象的context办法

DomainEventHandler

Cheddar/cheddar/cheddar-domain/src/main/java/com/clicktravel/cheddar/domain/event/DomainEventHandler.java

public interface DomainEventHandler extends EventHandler<DomainEvent> {

}

public interface HighPriorityDomainEventHandler extends DomainEventHandler {

}

public interface LowPriorityDomainEventHandler extends DomainEventHandler {

}

DomainEventHandler接口继承了EventHandler接口，其泛型为DomainEvent；HighPriorityDomainEventHandler及LowPriorityDomainEventHandler接口继承了DomainEventHandler接口

DomainEventPublisher

Cheddar/cheddar/cheddar-domain/src/main/java/com/clicktravel/cheddar/domain/event/DomainEventPublisher.java

public class DomainEventPublisher extends EventPublisher<DomainEvent> {

    private static DomainEventPublisher instance;

    public static void init(final MessagePublisher<TypedMessage> messagePublisher) {
        instance = new DomainEventPublisher(messagePublisher);
    }

    private DomainEventPublisher(final MessagePublisher<TypedMessage> messagePublisher) {
        super(messagePublisher);
    }

    public static DomainEventPublisher instance() {
        if (instance == null) {
            throw new IllegalStateException("DomainEventPublisher not initialized");
        }
        return instance;
    }

}

DomainEventPublisher继承了EventPublisher，其结构器接管MessagePublisher；它提供了init办法用于创立DomainEventPublisher，instance办法用于获取instance

小结

cheddar定义了DomainEvent接口及AbstractDomainEvent抽象类；DomainEventHandler接口继承了EventHandler接口，其泛型为DomainEvent；DomainEventPublisher继承了EventPublisher，其结构器接管MessagePublisher，其publishEvent办法最初通过MessagePublisher的publish来实现。

doc

• Cheddar