Developing a Scripted UA

This article explains how to develop a scripted User Application usable in the UA application built-in plugin. The UA must be coded using the Groovy scripting language. Groovy modules can have the same syntax as the Java language.

Content

Methods

A scripted UA is a groovy script file wich can have the following methods (all optional):

• public void init(): called when the UA Application is initialized
• public void start(): called when the UA Application is started
• public void subscribe(ServiceInstance): called when the UA Application is notified from one of the Services on which the UA is subscribed to
• public void push(ServiceInstance): called when the UA Application is called automatically for a cyclic invocation^[1]
  It is the case when a publish Service is called cyclically for the UA Application, for example: <cyclic service="position" frequency="100ms" />

The interface for the Script is Script.

Members

The script has three default members^[2]

They do not need to be declared in the script

:

• context: the Script context, which is an instance of the UAScriptContext class. See script context
• helper: the Script helper, which is an instance of the UAScriptHelper class. See script helper
• api: the ARINC 661 API. See ARINC 661 client API

Script context

The script context is an instance of the UAScriptContext class.

The Script context allows to:

• Get the ARINC 661 Client API: UAScriptContext.getAPI()
• Emit an error: UAScriptContext.error(String)
• Echo a message: UAScriptContext.echo(String)

Script helper

Several methods are provided in the UAScriptHelper class to get the values of the datas in the Service:

• Some methods do not take as argument the service name, and they will look for a Data in any Service
• Some methods take as argument the service name, those will look for values for the service which is explictly specified

Detecting if a data value has changed

There are two methods to detect if a Data value has changed:

• The UAScriptHelper.hasChanged(String) method return true if the data of a specified name has changed for any Service^[3]
  This will not work correctly if two Services have two different Datas of the same name
• The UAScriptHelper.hasChanged(String, String) method return true if the data of a specified name has changed for a specified Service

Getting a data value

There are two sets of methods to get the value of a Data:

• The getxxxValue(String) methods return the value of a Data in a specified type, if there is only one Service which has a Data with this name^[3]
  This will not work correctly if two Services have two different Datas of the same name
• The getxxxValue(String, String) methods return the value of a Data in a specified type for the a specified Service

For example:

• The UAScriptHelper.getFloatValue(String) method return the float value of the data of a specified name for any Service, if there is only one Service which has a Data with this name^[3]
  This will not work correctly if two Services have two different Datas of the same name
• The UAScriptHelper.hasChanged(String, String) method return the float value of the data of a specified name has changed for a specified Service

Setting a data value

To set the value for a Data, you should first get the Data of a specified name:

• The UAScriptHelper.getData(String) method return the data of a specified name, if there is only one Service which has a Data with this name^[3]
  This will not work correctly if two Services have two different Datas of the same name
• The UAScriptHelper.getData(String, String) method return the data of a specified name for a specified Service

Then you can set the value of this Data through the Data class. For example to set the value of a Data as a float:

• Data.setFloatValue(float)

Examples

For the defaultSubscribeService:

      public void subscribe(ServiceInstance service) {
        if (helper.hasChanged("value")) {
          String value = helper.getStringValue("value");
          api.setWidgetParameter(LAYER, LABEL, ARINC661.A661_STRING, value);
          api.sendAll();
        }
      }

For a specified service:

      public void subscribe(ServiceInstance service) {
        if (helper.hasChanged("publishedService", "value")) {
          String value = helper.getStringValue("publishedService", "value");
          api.setWidgetParameter(LAYER, LABEL, ARINC661.A661_STRING, value);
          api.sendAll();
        }
      }

Invoking Services

It is possible to invoke Services using the ServiceInstance.invoke() method.

For example:

      service.setDataBooleanValue("event", isSelected);
      service.invoke();

Comparison with Java User Applications

The content of a Groovy Script is very close to what you would write in a Java User Application. The main differences are:

• The logger is accessed through the script context. For example, the following code: logger.error(message) should be replaced by context.error(message)
• The methods in the AbstractFunctionalUA class are replaced by the equivalent methods in the UAScriptHelper class. For example, the following code:getStringValue("value"); should be replaced by helper.getStringValue("value");

Example

      int LAYER = 1;
      int TOGGLE_BUTTON = 1;
      int LABEL = 2;
      SendEventServiceInstance eventService = null;

      public void init() {
        this.eventService = (SendEventServiceInstance) context.getModule().getService("event");
        api.addWidgetEventListener(LAYER, TOGGLE_BUTTON, new ARINCEventListener() {
          public void eventReceived(ARINCEvent evt) {
            WidgetEvent widgetEvt = (WidgetEvent) evt;
            try {
              boolean isSelected = ((Boolean) widgetEvt.getValues().get(0));
              eventService.setDataBooleanValue("event", isSelected);
              eventService.invoke();
            } catch (ARINCRuntimeException ex) {
              context.error(ex.getMessage());
            }
          }
        });
      }

      public void subscribe(ServiceInstance service) {
        if (helper.hasChanged("value")) {
          String value = helper.getStringValue("value");
          api.setWidgetParameter(LAYER, LABEL, ARINC661.A661_STRING, value);
          api.sendAll();
        }
      }