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Variables in expressions and thread safety

Question asked by jcoveron on Jan 26, 2015
Latest reply on Jan 29, 2015 by trademak

I am using Java Service Task to get and set some processing variables. Here is an example:

public class Analysis {

   public void MediaInfoAction(DelegateExecution execution, String Nickname)
      EssenceMediaInfo MediaInfo = new EssenceMediaInfo();

      HashMap<String, String> NicknameDetails = MediaInfo.ParseNicknameProperties(execution, Nickname);

      String JsonString = "{"
            + "\"GeneralVideoCount\" : \"%VideoCount%\", "
            + "\"GeneralAudioCount\" : \"%AudioCount%\", "
            + "\"GeneralCompleteName\" : \"%CompleteName%\", "
            + "\"GeneralFormat\" : \"%Format%\", "
            + "\"GeneralFormatCommercial\" : \"%Format_Commercial%\", "
            + "\"GeneralFormatProfile\" : \"%Format_Profile%\", "
            + "\"GeneralFormatSettings\" : \"%Format_Settings%\", "
            + "\"GeneralFileExtension\" : \"%FileExtension%\", "
            + "\"GeneralFileSize\" : \"%FileSize%\", "
            + "\"GeneralOverallBitRateMode\" : \"%OverallBitRate_Mode%\", "
            + "\"GeneralOverallBitRateBps\" : \"%OverallBitRate%\", "
            + "\"GeneralOverallBitRateMbps\" : \"%OverallBitRate/String%\", "
            + "\"DidMediaInfoGeneralAnalysis\" : \"true\"}";
      JsonString = MediaInfo.GetFilePropertyByJson("General", JsonString);

      SetVariables(execution, JsonString);

   public void SetVariables(DelegateExecution execution, String JsonString) throws ParseException
      ContainerFactory containerFactory = new ContainerFactory()
         public List creatArrayContainer() {
           return new LinkedList();

          public Map createObjectContainer() {
            return new LinkedHashMap();
      Map json = (Map) this.JsonParser.parse(JsonString, containerFactory);
      Iterator iter = json.entrySet().iterator();
         Map.Entry entry = (Map.Entry);
         execution.setVariable(entry.getKey().toString(), entry.getValue().toString());


The same function can be called from multiple java service tasks executed after a parallel gateway within the same process instance. Also, the same process instance can be started multiple times and almost simultaneously.

As recommended in the user guide, we try to use only local variables inside the function, and we avoid using any member variables. This is because we want to achieve the java service task to execute concurrently.

Our parallel gateway have the activiti:async="true" activiti:exclusive="false" property as well as the java service tasks.

If we make the function thread safe (using synchronize), we cannot execute the task concurrently. But if we remove the thread safe (not using synchronize), the task is executed concurrently but variables values from a process instance are update by the values from another instance.

Our question is, how can we achieve the task concurrency and thread safety? Hope you can give us some tips on this.

The version we are using is 5.17.0.

We appreciate all your help in advance and congratulations on the software. It is very powerful.

Best regards