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Client library for working with the NATS messaging system.
There is a newer version: 2.20.5
// Copyright 2020 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.examples.jetstream;

import io.nats.client.*;
import io.nats.client.api.PublishAck;
import io.nats.examples.ExampleArgs;
import io.nats.examples.ExampleUtils;

/**
 * This example will demonstrate JetStream publishing with options.
 */
public class NatsJsPubWithOptionsUseCases {
    static final String usageString =
        "\nUsage: java -cp  NatsJsPubWithOptionsUseCases [-s server] [-strm stream] [-sub subject]"
            + "\n\nDefault Values:"
            + "\n   [-strm stream]     pubopts-stream"
            + "\n   [-sub subject]     pubopts-subject"
            + "\n\nUse tls:// or opentls:// to require tls, via the Default SSLContext\n"
            + "\nSet the environment variable NATS_NKEY to use challenge response authentication by setting a file containing your private key.\n"
            + "\nSet the environment variable NATS_CREDS to use JWT/NKey authentication by setting a file containing your user creds.\n"
            + "\nUse the URL in the -s server parameter for user/pass/token authentication.\n";

    public static void main(String[] args) {
        ExampleArgs exArgs = ExampleArgs.builder("Publish With Options Use Cases", args, usageString)
                .defaultStream("pubopts-stream")
                .defaultSubject("pubopts-subject")
                .build();

        try (Connection nc = Nats.connect(ExampleUtils.createExampleOptions(exArgs.server))) {
            // get a management context
            JetStreamManagement jsm = nc.jetStreamManagement();

            // Use the utility to create a stream stored in memory.
            NatsJsUtils.createStreamExitWhenExists(jsm, exArgs.stream, exArgs.subject);

            // get a regular context
            JetStream js = nc.jetStream();

            PublishOptions.Builder pubOptsBuilder = PublishOptions.builder()
                    .expectedStream(exArgs.stream)
                    .messageId("mid1");
            PublishAck pa = js.publish(exArgs.subject, "message1".getBytes(), pubOptsBuilder.build());
            System.out.printf("Published message on subject %s, stream %s, seqno %d.\n",
                    exArgs.subject, pa.getStream(), pa.getSeqno());

            // IMPORTANT!
            // You can reuse the builder in 2 ways.
            // 1. Manually set a field to null or to UNSET_LAST_SEQUENCE if you want to clear it out.
            // 2. Use the clearExpected method to clear the expectedLastId, expectedLastSequence and messageId fields

            // Manual re-use 1. Clearing some fields
            pubOptsBuilder
                    .expectedLastMsgId("mid1")
                    .expectedLastSequence(PublishOptions.UNSET_LAST_SEQUENCE)
                    .messageId(null);
            pa = js.publish(exArgs.subject, "message2".getBytes(), pubOptsBuilder.build());
            System.out.printf("Published message on subject %s, stream %s, seqno %d.\n",
                    exArgs.subject, pa.getStream(), pa.getSeqno());

            // Manual re-use 2. Setting all the expected fields again
            pubOptsBuilder
                    .expectedLastMsgId(null)
                    .expectedLastSequence(pa.getSeqno()) // last sequence can be found in last ack
                    .messageId("mid3");
            pa = js.publish(exArgs.subject, "message3".getBytes(), pubOptsBuilder.build());
            System.out.printf("Published message on subject %s, stream %s, seqno %d.\n",
                    exArgs.subject, pa.getStream(), pa.getSeqno());

            // reuse() method clears all the fields, then we set some fields.
            pubOptsBuilder.clearExpected()
                    .expectedLastSequence(pa.getSeqno()) // last sequence can be found in last ack
                    .messageId("mid4");
            pa = js.publish(exArgs.subject, "message4".getBytes(), pubOptsBuilder.build());
            System.out.printf("Published message on subject %s, stream %s, seqno %d.\n",
                    exArgs.subject, pa.getStream(), pa.getSeqno());

            // exception when the expected stream does not match [10060]
            try {
                PublishOptions opts = PublishOptions.builder().expectedStream("wrongStream").build();
                js.publish(exArgs.subject, "ex1".getBytes(), opts);
            } catch (JetStreamApiException e) {
                System.out.format("Exception was: '%s'\n", e);
            }

            // exception with wrong last msg ID [10070]
            try {
                PublishOptions opts = PublishOptions.builder().expectedLastMsgId("wrongId").build();
                js.publish(exArgs.subject, "ex2".getBytes(), opts);
            } catch (JetStreamApiException e) {
                System.out.format("Exception was: '%s'\n", e);
            }

            // exception with wrong last sequence [10071]
            try {
                PublishOptions opts = PublishOptions.builder().expectedLastSequence(999).build();
                js.publish(exArgs.subject, "ex3".getBytes(), opts);
            } catch (JetStreamApiException e) {
                System.out.format("Exception was: '%s'\n", e);
            }

            // delete the stream since we are done with it.
            jsm.deleteStream(exArgs.stream);
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}