Java tutorial
/* * 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.util.CharsetUtil; import io.netty.util.internal.ObjectUtil; /** * Mqtt version specific constant values used by multiple classes in mqtt-codec. */ public enum MqttVersion { MQTT_3_1("MQIsdp", (byte) 3), MQTT_3_1_1("MQTT", (byte) 4); private final String name; private final byte level; MqttVersion(String protocolName, byte protocolLevel) { name = ObjectUtil.checkNotNull(protocolName, "protocolName"); level = protocolLevel; } public String protocolName() { return name; } public byte[] protocolNameBytes() { return name.getBytes(CharsetUtil.UTF_8); } public byte protocolLevel() { return level; } public static MqttVersion fromProtocolNameAndLevel(String protocolName, byte protocolLevel) { for (MqttVersion mv : values()) { if (mv.name.equals(protocolName)) { if (mv.level == protocolLevel) { return mv; } else { throw new MqttUnacceptableProtocolVersionException( protocolName + " and " + protocolLevel + " are not match"); } } } throw new MqttUnacceptableProtocolVersionException(protocolName + "is unknown protocol name"); } }