Java example source code file (MqttCodecUtil.java)

This example Java source code file (MqttCodecUtil.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

connack, connect, max_client_id_length, min_client_id_length, mqttcodecutil, mqttfixedheader, pingresp, pubrec, pubrel, qos, subscribe, topic_wildcards, unsuback, unsubscribe

The MqttCodecUtil.java Java example source code

/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project licenses this file to you 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.netty.handler.codec.mqtt;

import io.netty.handler.codec.DecoderException;

final class MqttCodecUtil {

    private static final char[] TOPIC_WILDCARDS = {'#', '+'};
    private static final int MIN_CLIENT_ID_LENGTH = 1;
    private static final int MAX_CLIENT_ID_LENGTH = 23;

    static boolean isValidPublishTopicName(String topicName) {
        // publish topic name must not contain any wildcard
        for (char c : TOPIC_WILDCARDS) {
            if (topicName.indexOf(c) >= 0) {
                return false;
            }
        }
        return true;
    }

    static boolean isValidMessageId(int messageId) {
        return messageId != 0;
    }

    static boolean isValidClientId(MqttVersion mqttVersion, String clientId) {
        if (mqttVersion == MqttVersion.MQTT_3_1) {
            return clientId != null && clientId.length() >= MIN_CLIENT_ID_LENGTH &&
                clientId.length() <= MAX_CLIENT_ID_LENGTH;
        }
        if (mqttVersion == MqttVersion.MQTT_3_1_1) {
            // In 3.1.3.1 Client Identifier of MQTT 3.1.1 specification, The Server MAY allow ClientId’s
            // that contain more than 23 encoded bytes. And, The Server MAY allow zero-length ClientId.
            return clientId != null;
        }
        throw new IllegalArgumentException(mqttVersion + " is unknown mqtt version");
    }

    static MqttFixedHeader validateFixedHeader(MqttFixedHeader mqttFixedHeader) {
        switch (mqttFixedHeader.messageType()) {
            case PUBREL:
            case SUBSCRIBE:
            case UNSUBSCRIBE:
                if (mqttFixedHeader.qosLevel() != MqttQoS.AT_LEAST_ONCE) {
                    throw new DecoderException(mqttFixedHeader.messageType().name() + " message must have QoS 1");
                }
            default:
                return mqttFixedHeader;
        }
    }

    static MqttFixedHeader resetUnusedFields(MqttFixedHeader mqttFixedHeader) {
        switch (mqttFixedHeader.messageType()) {
            case CONNECT:
            case CONNACK:
            case PUBACK:
            case PUBREC:
            case PUBCOMP:
            case SUBACK:
            case UNSUBACK:
            case PINGREQ:
            case PINGRESP:
            case DISCONNECT:
                if (mqttFixedHeader.isDup() ||
                        mqttFixedHeader.qosLevel() != MqttQoS.AT_MOST_ONCE ||
                        mqttFixedHeader.isRetain()) {
                    return new MqttFixedHeader(
                            mqttFixedHeader.messageType(),
                            false,
                            MqttQoS.AT_MOST_ONCE,
                            false,
                            mqttFixedHeader.remainingLength());
                }
                return mqttFixedHeader;
            case PUBREL:
            case SUBSCRIBE:
            case UNSUBSCRIBE:
                if (mqttFixedHeader.isRetain()) {
                    return new MqttFixedHeader(
                            mqttFixedHeader.messageType(),
                            mqttFixedHeader.isDup(),
                            mqttFixedHeader.qosLevel(),
                            false,
                            mqttFixedHeader.remainingLength());
                }
                return mqttFixedHeader;
            default:
                return mqttFixedHeader;
        }
    }

    private MqttCodecUtil() { }
}