关闭旧实例

agri-framework/src/main/java/com/agri/framework/config/MqttConfig.java

@@ -218,11 +218,17 @@ public class MqttConfig {
     // 新增：应用关闭时优雅断开MQTT连接，避免连接泄漏（JDK 8兼容）
     @PreDestroy
     public void destroyMqttClient() {
-        if (mqttClientInstance != null && mqttClientInstance.isConnected()) {
+        // 最小改动：补充判空+close+置空，保留原有逻辑和注释
+        if (mqttClientInstance != null) {
             try {
+                if (mqttClientInstance.isConnected()) {
                     mqttClientInstance.disconnect();
-                mqttClientInstance.close();
                     log.info("【MQTT连接关闭】客户端已优雅断开连接");
+                }
+                // 新增：关闭实例释放资源
+                mqttClientInstance.close();
+                // 新增：置空实例加速GC
+                mqttClientInstance = null;
             } catch (MqttException e) {
                 log.error("【MQTT连接关闭异常】：" + e.getMessage(), e);
             }

agri-framework/src/main/java/com/agri/framework/interceptor/MqttMessageHandler.java

@@ -448,14 +448,16 @@ public class MqttMessageHandler implements SmartLifecycle {
                 currentReconnectCount++;
                 log.info("【MQTT重连】第{}次尝试重连（间隔{}秒）", currentReconnectCount, reconnectInterval);
 
-                // 兼容极端场景：先强制断开（无论当前状态），再重新连接
+                // 最小改动：补充close+置空，彻底释放旧实例
                 try {
                     if (mqttClient.isConnected()) {
                         mqttClient.disconnect();
                         log.info("【MQTT重连】已断开旧连接");
                     }
+                    // 新增：关闭旧实例释放资源
+                    mqttClient.close();
                 } catch (Exception e) {
-                    log.warn("【MQTT重连】断开旧连接失败（忽略）：{}", e.getMessage());
+                    log.warn("【MQTT重连】断开/关闭旧连接失败（忽略）：{}", e.getMessage());
                 }
 
                 // 2. 生成新的clientId（和MqttConfig中一致的规则：原clientId + 随机后缀）