OpenHAB中ECMAScript脚本首次运行成功后报错求助

平台信息 #

Hardware: Synology with docker
OS: Linux/4.4.302+ (amd64)
Java Runtime Environment: debian 17.0.12
openHAB version: openHAB 4.2.2

问题描述 #

配置了一条OpenHAB规则，当加热控件修改evohome恒温器的设定值时触发。规则采用ECMAScript(v11)编写，逻辑是将变量与项目值转换为JSON字符串，发布到MQTT代理的命令主题。首次触发时脚本运行正常，能成功发布消息并修改设定值，但之后脚本失效，必须重新初始化脚本引擎才能再次正常运行一次，无法定位问题原因。

已在多个论坛查找Javascript/JSON/MQTT/Graalvm/Openhab相关主题，但未找到针对OpenHAB 4中MQTT与evohome结合的相关讨论，确认代码可成功运行但仅能生效一次。

完整规则代码 #

configuration: {}
triggers:
  - id: "1"
    configuration:
      itemName: Thermostaat_zone_temperature_setpoint
    type: core.ItemStateUpdateTrigger
conditions: []
actions:
  - inputs: {}
    id: "2"
    configuration:
      type: application/javascript
      script: >-
        var item = items.Thermostaat_zone_temperature_setpoint;

        var obj = new Object();

        obj.command = "set_zone_setpoint";

        obj.setpoint = item.state;

        obj.zone_idx = 1;

        obj.ctl_id = "ID";

        var val = parseFloat (obj.setpoint);

        obj.setpoint = val;

        var message = JSON.stringify(obj);

        var actions = actions.get("mqtt", "mqtt:broker:master");

        actions.publishMQTT("evohome/evogateway/_zone_independent/command",
        message);

        console.log(message);
    type: script.ScriptAction

运行日志 #

成功运行日志 #

2024-10-17 20:17:02.354 [DEBUG] [.internal.OpenhabGraalJSScriptEngine] - Initializing GraalJS script engine...
2024-10-17 20:17:02.360 [DEBUG] [.internal.OpenhabGraalJSScriptEngine] - Injecting ThreadsafeTimers into the JS runtime...
2024-10-17 20:17:02.361 [DEBUG] [.internal.OpenhabGraalJSScriptEngine] - Evaluating cached global script...
2024-10-17 20:17:02.362 [DEBUG] [.internal.OpenhabGraalJSScriptEngine] - Evaluating cached openhab-js injection...
2024-10-17 20:17:02.417 [DEBUG] [.internal.OpenhabGraalJSScriptEngine] - Successfully initialized GraalJS script engine.
2024-10-17 20:17:02.420 [INFO ] [ab.automation.script.ui.evo_zone] - {"command":"set_zone_setpoint","setpoint":20.5,"zone_idx":1,"ctl_id":"id code"}
2024-10-17 20:17:02.420 [DEBUG] [ing.mqtt.internal.action.MQTTActions] - MQTT publish to evohome/evogateway/_zone_independent/command performed

失败运行日志 #

2024-10-18 06:51:42.850 [ERROR] [internal.handler.ScriptActionHandler] - Script execution of rule with UID 'evo_zone' failed: org.graalvm.polyglot.PolyglotException: TypeError: invokeMember (get) on org.openhab.binding.mqtt.internal.action.MQTTActions@27c6d6d2 failed due to: Unknown identifier: get
2024-10-18 06:54:44.350 [ERROR] [ation.script.javascript.evo_eetkamer] - Failed to execute script: TypeError: invokeMember (get) on org.openhab.binding.mqtt.internal.action.MQTTActions@27c6d6d2 failed due to: Unknown identifier: get
        at <js>.:program(<eval>:10)
        at org.graalvm.polyglot.Context.eval(Context.java:399)
        at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:458)
        at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:426)
        at java.scripting/javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:262)

问题解决 #

错误根源是脚本覆盖了全局的actions变量：
首次运行时，actions是OpenHAB提供的全局动作服务对象，调用actions.get()能获取到MQTT动作实例并赋值给同名变量actions。但第二次运行时，脚本里的actions已经是上一次保存的MQTT动作实例，这个实例并没有get方法，因此抛出Unknown identifier: get错误。

修改方法是将获取MQTT动作的变量名改为其他名称，避免覆盖全局变量，比如mqttActions：

修改后的脚本关键部分：

var message = JSON.stringify(obj);

// 改用不同变量名，不覆盖全局actions
var mqttActions = actions.get("mqtt", "mqtt:broker:master");

mqttActions.publishMQTT("evohome/evogateway/_zone_independent/command", message);

console.log(message);

这样每次运行脚本时，都会通过全局的actions服务获取MQTT动作实例，不会出现变量覆盖导致的错误。

内容的提问来源于stack exchange，提问作者AlexanderR1987