SWF：基於無極

Question

結束工作流程我有一個調用活動決勝局。該活動返回驗證錯誤列表。如果決策者收到該列表並且它不是空的，我想退出工作流程。

要退出工作流程，我可以只返回在決勝局，並退出工作流程。問題是我無法從活動中獲得結果。我會希望這個工作，但它不.. violations.isReady（）總是返回false：

public class WorkflowImpl implements Workflow { 
    ActivitiesClient activities; 

    public Workflow(/*...*/) { 
     // ... 
    } 

    @Override 
    public void do(WorkflowInput input) { 
     Promise<List<String>> violations = activities.validate(input); 

     if (!violations.isReady()) { // "do()" will be called when violations is ready.. right? 
      return; 
     } else if (!CollectionUtils.isEmpty(violations.get())) { 
      return; // or throw ValidationException 
     } 

     // do other stuff 
    } 
} 

我不想做替代這是輪詢violations.isReady（ ）是真實的，因爲這將會爲決定者線索誰知道多久。我甚至不確定這是否可行。

幫助？

Answer 1

工作流的代碼是異步的。因此從活動返回的Promise從未準備好在相同的回調中。因此，在你的代碼violations.isReady（）總是返回假是正確的行爲。 你必須使用註解爲@Asynchronous或任務來回調關聯到無極的方法。所以，你的代碼應該是這樣的：

public class WorkflowImpl implements Workflow { 
    ActivitiesClient activities; 

    public Workflow(/*...*/) { 
     // ... 
    } 

    @Override 
    public void do(WorkflowInput input) { 
    Promise<List<String>> violations = activities.validate(input); 
    processValidationResult(violations); 
    } 

    @Asynchronous 
    private void processValidationResult(Promise<List<String>> violations) { 
    // As method is @Asynchronous framework guarantees violations is ready 
    // when its body is executed. 
    if (!CollectionUtils.isEmpty(violations.get())) { 
     return; // or throw ValidationException 
    } 
    // do other stuff 
    } 
} 

注意，AspectJ的should be configured correctly與流程框架方面的@Asynchronous註解生效。

另一種選擇是直接使用任務：

public class WorkflowImpl implements Workflow { 
    ActivitiesClient activities; 

    public Workflow(/*...*/) { 
     // ... 
    } 

    @Override 
    public void do(WorkflowInput input) { 
    Promise<List<String>> violations = activities.validate(input); 
    new Task(violations) { 
     @Override 
     public void doExecute() { 
     // Framework guarantees violations is ready 
     // (as it is Task constructor parameter) 
     // when execute method is executed. 
     if (!CollectionUtils.isEmpty(violations.get())) { 
      return; // or throw ValidationException 
     } 
     // do other stuff 
     } 
    }; 
    } 
} 

我會建議通過SWF Recipes和samples閱讀來獲取有關編寫SWF工作流程時使用的模式更好的主意。

另外，還要確保你通過TryCatchFinally javadoc作爲AWS流程框架的錯誤處理，同時非常強大的是大多數人都習慣完全不同。

加到顯示例如從processValidationResult（...）返回值：

@Override 
    public void do(WorkflowInput input) { 
    Promise<List<String>> violations = activities.validate(input); 
    Promise<String> whatever = processValidationResult(violations); 
    processNextStep(whatever); 
    } 

    @Asynchronous 
    private Promise<String> processValidationResult(Promise<List<String>> violations) { 
    // As method is @Asynchronous framework guarantees violations is ready 
    // when its body is executed. 
    if (!CollectionUtils.isEmpty(violations.get())) { 
     throw new ValidationException(...); 
    } 
    // do other stuff 
    return Promise.asPromise("result string"); 
    } 

    @Asynchronous 
    private void processNextStep(Promise<String> whatever) { 
    ... 
    }