以下是一个使用Axon框架进行事件处理程序从偏移量恢复的示例代码:
import org.axonframework.common.transaction.TransactionManager;
import org.axonframework.eventhandling.EventMessage;
import org.axonframework.eventhandling.EventTrackerStatus;
import org.axonframework.eventhandling.TrackingEventProcessor;
import org.axonframework.eventhandling.tokenstore.TokenStore;
import org.axonframework.serialization.SerializedObject;
import org.axonframework.serialization.Serializer;
public class EventProcessorOffsetRecovery {
private final TrackingEventProcessor trackingEventProcessor;
private final TokenStore tokenStore;
private final TransactionManager transactionManager;
private final Serializer serializer;
public EventProcessorOffsetRecovery(TrackingEventProcessor trackingEventProcessor,
TokenStore tokenStore,
TransactionManager transactionManager,
Serializer serializer) {
this.trackingEventProcessor = trackingEventProcessor;
this.tokenStore = tokenStore;
this.transactionManager = transactionManager;
this.serializer = serializer;
}
public void recoverFromOffset(long offset) {
EventTrackerStatus eventTrackerStatus = trackingEventProcessor.processingStatus();
if (eventTrackerStatus.isReplaying()) {
throw new IllegalStateException("Cannot recover offset while replaying events");
}
transactionManager.executeInTransaction(() -> {
eventTrackerStatus.restartTracking();
tokenStore.fetchSegments(trackingEventProcessor.getName())
.forEach(segment -> tokenStore.storeToken(
trackingEventProcessor.createTokenAt(offset),
segment,
trackingEventProcessor.getName()
));
});
}
public void processEvent(EventMessage> eventMessage) {
SerializedObject serializedObject = serializer.serialize(eventMessage, byte[].class);
trackingEventProcessor.processingStatus().eventProcessor().eventHandlerInvoker()
.handle(serializer.deserialize(serializedObject));
}
}
这个代码示例中,首先定义了一个 EventProcessorOffsetRecovery
类,它接受一个 TrackingEventProcessor
实例、一个 TokenStore
实例、一个 TransactionManager
实例和一个 Serializer
实例作为参数。
recoverFromOffset
方法用于从给定的偏移量恢复事件处理程序的状态。它会检查当前的事件处理程序是否正在回放事件,如果是,则会抛出异常。然后,在事务中重启事件处理程序的跟踪状态,并将偏移量存储到令牌存储中,以便事件处理程序从指定的偏移量开始处理事件。
processEvent
方法用于处理单个事件消息。它首先将事件消息序列化为字节数组,然后使用事件处理程序的事件处理程序调用程序来处理反序列化后的事件消息。
请注意,上述代码示例仅提供了一个基本的框架,具体的实现可能因使用的Axon版本和其他细节而有所不同。因此,您可能需要根据自己的需求进行适当的调整。