Asynchronous execution

[dimaa6]

This pull request resolves #172 . It introduces ability to skip executing request by server or client immediately, and allows to complete it at later time by invoking new methods of IClient and IServer interfaces:

IClient:

boolean asyncCompleteRequest(String uniqueId, Confirmation confirmation) throws UnsupportedFeatureException, OccurenceConstraintException;

IServer:

boolean asyncCompleteRequest(UUID sessionIndex, String uniqueId, Confirmation confirmation)
      throws NotConnectedException, UnsupportedFeatureException, OccurenceConstraintException;

Changes are not breaking, existing code will continue to work without any need for modification. Usage of new methods and asynchronous mode are fully optional. The following diagram provides an example of using the asynchronous mode:

It also resolves #86 by allowing client to call asyncCompleteRequest in handleTriggerMessageRequest before sending a message requested by TriggerMessageRequest, and finally return null from handleTriggerMessageRequest.

One serious change is that in order to know OCPP message ID of the request in its handler, it has been included into every class which implemented Request interface. I enhanced Request interface with getOcppMessageId and setOcppMessageId methods, and implemented them in abstract class RequestWithId which implements Request. Then every class which formerly implemented Request interface now extends RequestWithId. Now handler implementation can simple call getOcppMessageId on the instance of Request it got. I have taken measures to not include ocppMessageId into serialized message, by introducing Exclude annotation.

[TVolden]

Hi @dimaa6,

First of all, thank you for your contribution.
I'll try to review the code this evening and get back to you.

Sincerely,
Thomas Volden

[TVolden]

Looks fine

[TVolden]

The method only returns true or throws an exception. Should probably just make it void. This would also conform to the CQS principle.

[dimaa6]

It may return false if it did not find pending promise:

Java-OCA-OCPP/ocpp-common/src/main/java/eu/chargetime/ocpp/Session.java

Lines 251 to 256 in b6c0b59

	synchronized (pendingPromises) {
	promiseAction = pendingPromises.get(id);
	if (promiseAction == null) return false;
	// remove promise from store
	pendingPromises.remove(id);
	}

[TVolden]

Hi @dimaa6,

I have merged it into the main. Thank you for the contribution, it really means a lot to me.

Sincerely,
Thomas Volden

[mf-fujimori]

Hi @dimaa6
May I ask a question?

I believe that when the server sends a message, a uniqueId is assigned to the request.

The server needs the uniqueId when it calls "asyncCompleteRequest".

Where is "setOcppMessageId" called when the message is sent?

[dimaa6]

Hi @dimaa6 May I ask a question?

I believe that when the server sends a message, a uniqueId is assigned to the request.

The server needs the uniqueId when it calls "asyncCompleteRequest".

Where is "setOcppMessageId" called when the message is sent?

You mean this line?

https://github.com/ChargeTimeEU/Java-OCA-OCPP/blob/master/ocpp-common/src/main/java/eu/chargetime/ocpp/Session.java#L218

[mf-fujimori]

Thank you for your response.

https://github.com/ChargeTimeEU/Java-OCA-OCPP/blob/master/ocpp-common/src/main/java/eu/chargetime/ocpp/Session.java#L218

I believe this is the process upon receipt.

An ID is generated when a message is sent.
I would like to know where this is the ID that is set in Request.
https://github.com/ChargeTimeEU/Java-OCA-OCPP/blob/master/ocpp-common/src/main/java/eu/chargetime/ocpp/Server.java#L219

[dimaa6]

Thank you for your response.

https://github.com/ChargeTimeEU/Java-OCA-OCPP/blob/master/ocpp-common/src/main/java/eu/chargetime/ocpp/Session.java#L218

I believe this is the process upon receipt.

An ID is generated when a message is sent. I would like to know where this is the ID that is set in Request. https://github.com/ChargeTimeEU/Java-OCA-OCPP/blob/master/ocpp-common/src/main/java/eu/chargetime/ocpp/Server.java#L219

Yes, ID is generated when the request is sent, you have identified the line correctly. But I still don't understand the question. Let me try to provide the information I have. Session still handles the received message, code on server and client side is the same. And setOcppMessageId is called on receiving side, not the sending side. Then client code which handles the message will have the ID and will be able to call asyncCompleteRequest. Does this answer your question?

[mf-fujimori]

I am sorry that my question is not clear.
What I am asking is if it is possible to use "asyncCompleteRequest" to send a message from the server and cancel it if no response is returned.
I want to remove it because the library will continue to have Promise if no response is returned.

[dimaa6]

I am sorry that my question is not clear. What I am asking is if it is possible to use "asyncCompleteRequest" to send a message from the server and cancel it if no response is returned. I want to remove it because the library will continue to have Promise if no response is returned.

You may create a pull request with new method which will remove promise by ID, similarly to asyncCompleteRequest but without actually completing it.

[matssom]

I might be understanding wrong, but in the example bellow (from OCPP 1.6 example) it seems like returning null means unsupported feature, not "I'll handle response later". Is this an outdated example or am I misunderstanding?

@Override
public RemoteStartTransactionConfirmation handleRemoteStartTransactionRequest(RemoteStartTransactionRequest request) {

    System.out.println(request);
    // ... handle event

    return null; // returning null means unsupported feature
}