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Client library for working with the NATS messaging system.

There is a newer version: 2.20.5

// Copyright 2020-2023 The NATS Authors
// 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.nats.client;

/**
 * A fetch consumer gets messages by calling nextMessage.
 * nextMessage returns null when there are no more messages
 */
public interface FetchConsumer extends MessageConsumer {
    /**
     * Read the next message. Return null if the fetch has been fulfilled either
     * because max messages or bytes max bytes have been reached,
     * or because the fetch was not fulfilled in the timeout set by the fetch options.
     * @return the next message for this subscriber or null if there is a timeout
     * @throws InterruptedException if one is thrown, in order to propagate it up
     * @throws JetStreamStatusCheckedException an exception representing a status that requires attention,
     *         such as the consumer was deleted on the server in the middle of use.
     */
    Message nextMessage() throws InterruptedException, JetStreamStatusCheckedException;
}