What’s New in Dromara mica-mqtt 2.4.5? Upgrade Guide and Key Features

1. Introduction

Dromara mica-mqtt 2.4.5 official release is out. Starting from version 2.4.x the Maven groupId has moved to org.dromara.mica-mqtt, package name to org.dromara, other usage remains the same. Strongly recommend upgrading to the new 2.4.x.

Because the old documentation was scattered, a new documentation site has been added: https://mica-mqtt.dromara.org

2. Changelog

v2.4.5 – 2025-05-06

✨ mica-mqtt-client-spring-boot-starter now supports custom deserialization for @MqttClientSubscribe annotation.

✨ Optimized code; Spring Boot client can customize MqttClientSubscribeDetector (thanks @galaxy-sea).

✨ Upgraded mica-net to 1.1.6, fixing Eclipse Paho MQTT WebSocket client errors.

✨ Dependency adjustments reduce security warnings in example projects.

🐛 Fixed client reconnection issue when messages are sent during server restart (thanks @wtjperi2003).

🐛 Fixed Netty MQTT codec assignment error of maxQoS parameter in ConnAck Properties.

v2.4.4 – 2025-04-13

✨ mica-mqtt-server now better compatible with Android (thanks @KittenBall).

v2.4.3 – 2025-03-23

✨ Central Portal now supports snapshots (90‑day storage, auto‑publish on dev branch).

✨ Code cleanup, removed unused parts, moved to mica-net.

✨ Added heartbeatMode and heartbeatTimeoutStrategy to client for weak‑network scenarios.

✨ mica-mqtt-server now depends on mica-net-http by default, simplifying usage.

✨ Exposed getMqttServer() method in MqttServerTemplate.

✨ Server starter now tolerates missing MeterRegistry bean.

3. Key Notes

In version 2.4.5, the @MqttClientSubscribe annotation in mica-mqtt-client-spring-boot-starter adds a deserialization attribute defaulting to JSON. Users can implement MqttDeserializer for custom serialization. The annotation also supports parameter binding by type as follows:

/** 
 * @param topic  mqtt topic
 * @param message mqtt raw message
 * @param data user‑defined java bean
 */
@MqttClientSubscribe(
    value = "/test/json",
    deserialize = MqttJsonDeserializer.class // default JSON deserializer from 2.4.5
)
public void testJson(String topic, MqttPublishMessage message, TestJsonBean data) {
    // 2.4.5 supports 2‑3 parameters with mapping rules:
    // String → topic, MqttPublishMessage → raw message (including MQTT5 props),
    // byte[] / ByteBuffer → payload, other types → JSON serialization
    logger.info("topic:{} json data:{}", topic, data);
}

4. Documentation

MQTT basics, MQTTX, mica-mqtt usage videos

mica-mqtt quick start guide

Frequently asked questions

Release versions

Migration guide for older versions

5. Open‑Source Repositories

Gitee: https://gitee.com/dromara/mica-mqtt

GitHub: https://github.com/dromara/mica-mqtt

GitCode: https://gitcode.com/dromara/mica-mqtt

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Interface Overview:

Official site: https://iot.bladex.cn

Demo site: https://iot.javablade.com