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本文次要钻研一下cheddar的events

Event

Cheddar/cheddar/cheddar-events/src/main/java/com/clicktravel/cheddar/event/Event.java

public interface Event {    String type();    String serialize();}
Event接口定义了type、serialize办法

AbstractEvent

Cheddar/cheddar/cheddar-events/src/main/java/com/clicktravel/cheddar/event/AbstractEvent.java

public abstract class AbstractEvent implements Event {    private static final ObjectMapper MAPPER = new ObjectMapper();    static {        MAPPER.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);        MAPPER.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);        MAPPER.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);        MAPPER.registerModule(new JodaModule());    }    @Override    public abstract String type();    public static <T extends Event> T newEvent(final Class<T> eventClass, final String serializedEvent) {        try {            return MAPPER.readValue(serializedEvent, eventClass);        } catch (final IOException e) {            throw new IllegalStateException("Could not instantiate event " + eventClass.getName());        }    }    @Override    public final String serialize() {        try {            return MAPPER.writeValueAsString(this);        } catch (final Exception e) {            throw new IllegalStateException("Could not serialize event: [" + this + "]", e);        }    }}
AbstractEvent申明实现Event接口，它实现了serialize办法，采纳jackson序列化为json；而后申明type形象办法供子类实现

EventHandler

Cheddar/cheddar/cheddar-events/src/main/java/com/clicktravel/cheddar/event/EventHandler.java

public interface EventHandler<E extends Event> {    void handle(final E event);    Class<? extends E> getEventClass();}
EventHandler接口定义了handle、getEventClass办法

EventPublisher

Cheddar/cheddar/cheddar-events/src/main/java/com/clicktravel/cheddar/event/EventPublisher.java

public abstract class EventPublisher<E extends Event> {    private final Logger logger = LoggerFactory.getLogger(getClass());    private final MessagePublisher<TypedMessage> messagePublisher;    protected EventPublisher(final MessagePublisher<TypedMessage> messagePublisher) {        this.messagePublisher = messagePublisher;    }    public void publishEvent(final E event) {        logger.debug("Publishing: " + event);        final TypedMessage typedMessage = new SimpleMessage(event.type(), event.serialize());        messagePublisher.publish(typedMessage);    }}
EventPublisher办法定义了publishEvent办法，它创立SimpleMessage，而后执行messagePublisher的publish来公布音讯

小结

cheddar定义了Event接口及AbstractEvent抽象类，其子类须要实现type办法；EventHandler接口定义了handle、getEventClass办法；EventPublisher办法定义了publishEvent办法，它创立SimpleMessage，而后执行messagePublisher的publish来公布音讯。

doc

  • Cheddar