io.axoniq.axonserver.connector.query.QueryHandler Maven / Gradle / Ivy
/*
* Copyright (c) 2020. AxonIQ
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.axoniq.axonserver.connector.query;
import io.axoniq.axonserver.connector.Registration;
import io.axoniq.axonserver.connector.ReplyChannel;
import io.axoniq.axonserver.grpc.query.QueryRequest;
import io.axoniq.axonserver.grpc.query.QueryResponse;
import io.axoniq.axonserver.grpc.query.QueryUpdate;
import io.axoniq.axonserver.grpc.query.SubscriptionQuery;
/**
* Interface representing a component that can handle queries.
*/
@FunctionalInterface
public interface QueryHandler {
/**
* Handle the given {@code query}, using given {@code responseHandler} to send the response(s).
*
* Note that the query must be completed using {@link ReplyChannel#complete()} or {@link
* ReplyChannel#sendLast(Object)}.
*
* @param query the message representing the query request
* @param responseHandler to handler to send responses with
*/
void handle(QueryRequest query, ReplyChannel responseHandler);
/**
* Registers an incoming subscription query request, represented by given {@code query}, using given {@code
* updateHandler} to send updates when the projection for this query changes.
*
* If this handler doesn't support subscription queries for the given {@code query}, it should return {@code null}.
* Otherwise, it must return a handle that can be used to cancel the subscription query.
*
* @param query the message representing the query
* @param updateHandler to handler to send updates with
* @return a registration to cancel the subscription, or {@code null} if this handler doesn't support the
* subscription query
*/
default Registration registerSubscriptionQuery(SubscriptionQuery query, UpdateHandler updateHandler) {
return null;
}
/**
* Interface describing a stream of updates to a subscription query.
*/
interface UpdateHandler {
/**
* Send the given {@code queryUpdate} in response to the subscription query this handler was provided for.
*
* @param queryUpdate the update to send
*/
void sendUpdate(QueryUpdate queryUpdate);
/**
* Indicates the subscription query has completed, meaning no more updates are to be expected. The component
* sending the subscription query is requested to close the subscription.
*/
void complete();
}
}