Stack Overflow when using Topicfilter with a large number of levels.

[sauroter]

Expected behavior

Client handles subscriptions with a large amount of topic levels gracefully.

Actual behavior

java.lang.StackOverflowError in com.hivemq.client.internal.mqtt.handler.subscribe.MqttSubscriptionHandler.

To Reproduce

Steps

1. Set up a MQTT broker on localhost.
2. Run reproducer code.

Reproducer code

public class Main {

    public static void main(String[] args) {

        final Mqtt5BlockingClient client = MqttClient.builder()
                .identifier(UUID.randomUUID().toString())
                .serverHost("localhost")
                .useMqttVersion5()
                .build().toBlocking();

        client.connect();

        final StringBuilder basis = new StringBuilder("/");

        for (int i = 0; i < 16; i++) {
            final String string = basis.toString();
            System.err.println("Rotation: " + i + " StringSize=" + string.length());
            final MqttTopicFilter filter = MqttTopicFilter.of(string);
            client.subscribeWith().topicFilter(filter).send();
            client.unsubscribeWith().addTopicFilter(filter).send();
            basis.append(basis);
        }
    }
}

Details

• Affected HiveMQ MQTT Client version(s):

        <dependency>
            <groupId>com.hivemq</groupId>
            <artifactId>hivemq-mqtt-client</artifactId>
            <version>1.1.2</version>
        </dependency>

• Used JVM version:

openjdk version "11.0.4" 2019-07-16
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.4+11)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.4+11, mixed mode)