Hi Andrey,
I just had a second look at your proposed changes. I really like them.
I was already sort of getting annoyed by having the need to use the
PlcReader.read() method to do the read and do think your suggestion is a good
one.
One thing we could think about, would be to move all classes in the "spi" package outside
the "api" module. I couldn't find any references to them from within the rest of the
package.
I think the driver-base might be a good home for them.
What do you think?
Chris
Am 04.10.18, 16:34 schrieb "Andrey Skorikov" <[email protected]>:
Hello all,
I propose to refactor the PLC4J API and move operations PlcReader.read,
PlcWriter.write and PlcSubscriber.{subscribe,unsubscribe} for submitting
requests to the PLC away from these interfaces and place one execute()
operation directly on the request type. This has already been discussed
in the mailing list, but no decision to implement the change was made.
I have implemented the proposal in a separate branch and created a pull
request to review the changes. Additional details can be found in the
description of the pull request in github.
Best regards,
Andrey
On 09/13/2018 11:42 AM, Sebastian Rühl wrote:
> Hey Andrey,
>
> Currently I have added a convenience method for my purposes on the
interface which makes it easier to write requests:
> CompletableFuture<PlcReadResponse<?>> response = reader.read(builder ->
builder.addItem("station", "Allgemein_S2.Station:BYTE"));
> This way you are not required to write the same code over again. Maybe
this helps a bit?
>
> Sebastian
>
>> Am 13.09.2018 um 10:49 schrieb Andrey Skorikov
<[email protected]>:
>>
>> Hi,
>>
>> I believe that if we move the execute() operation to requests, we could
also get rid of PlcReader/PlcWriter interfaces altogether, since otherwise they would
degenerate to very thin interfaces containing nothing but a single factory method for
obtaining PlcReadRequest.Builders. So, in order to execute a read request, instead of:
>>
>> PlcReader reader = connection.getReader().get(); // ignore .get() for a
moment
>> PlcReadRequest request =
reader.readRequestBuilder().addItem(...).build();
>> reader.read(request);
>>
>> we could write:
>>
>> connection.readRequestBuilder().get().addItem(...).build().execute();
>>
>> Best regards,
>> Andrey
>>
>>
>> On 09/12/2018 06:21 PM, Christofer Dutz wrote:
>>> Hi,
>>>
>>> This correlation was just a convenience at the start. I never really
liked it, but wasn't annoying enough to do it.
>>>
>>> I would strongly opt for splitting it up into separate classes.
Especially as it generally allows producing read-only only driver versions by excluding
classes from the lib.
>>>
>>> Chris
>>>
>>> Outlook for Android<https://aka.ms/ghei36> herunterladen
>>>
>>> ________________________________
>>> From: Andrey Skorikov <[email protected]>
>>> Sent: Wednesday, September 12, 2018 4:58:12 PM
>>> To: [email protected]
>>> Subject: Re: Define execute operation on Request; remove read/write
operations from Reader/Writer
>>>
>>> Hi Chris,
>>>
>>> no need for a factory-factory. :) I believe that the core problem is
>>> that the PlcConnection interface does too much - it offers
>>> protocol-specific transport functionality by providing the
>>> PlcReader.read operation, it maintains protocol state, and it serves as
>>> a factory for read requests (through PlcReader.readRequestBuilder).
>>>
>>> Another problem is that the requests, which are obtained through the
>>> ReadRequestBuilder are basically independent from a concrete connection
>>> instance. Hence it does not make sense to obtain a Builder instance
from
>>> a PlcConnection. For example, consider the following scenario: first we
>>> obtain a PlcConnection, PlcReader and a RequestBuilder off it. Then we
>>> close the PlcConnection. What should happen, if we build and try to
>>> execute requests from that RequestBuilder? Should it return request
>>> instances but throw exceptions when we try to execute them on another
>>> (live) connection? Or should it throw exceptions when we call build()?
>>> Or should it allow us to execute the built requests on another
>>> connection? In the latter case, why should be forced to obtain a
request
>>> builder from a connection instance anyway?
>>>
>>> Best regards,
>>> Andrey
>>>
>>>
>>> On 09/12/2018 04:21 PM, Christofer Dutz wrote:
>>>> Hi Andrey,
>>>>
>>>> are you proposing a Factory-Factory? Wouldn't that go a little too
far? Currently the request factory method being in the connection, is just an
implementation detail we could have a S7Reader class implementing the Reader interface and
this is generated from the connection, if this is the problem.
>>>>
>>>> Chris
>>>>
>>>> Am 12.09.18, 15:54 schrieb "Andrey Skorikov"
<[email protected]>:
>>>>
>>>> Hi Sebastian,
>>>>
>>>> good point! The mutability of PlcReadRequest would be a
consequence of
>>>> the mutability of the PlcConnection (or something that can
handle the
>>>> execute). However, in order to construct a immutable
PlcReadRequest,
>>>> currently we still need to obtain a PlcRequest.Builder from the
same
>>>> mutable PlcConnection. I think, if we really want
PlcReadRequest to be
>>>> immutable, then we should be able to construct them
independently (not
>>>> from a mutalbe object). Perhaps we could separate PlcRequest
>>>> construction from its exection by providing a RequestBuilder
factory
>>>> method not on a mutable PlcConnection but "higher up", for
example
>>>> somewhere on a PlcDriver?
>>>>
>>>> Regards,
>>>> Andrey
>>>>
>>>> On 09/12/2018 03:33 PM, Sebastian Rühl wrote:
>>>> > Hey Andrey,
>>>> >
>>>> > One thing that would stand against this: Adding a execute()
would make the PlcReadRequest mutable which is a thing we should avoid (Mutable because it
would need a reference store to something that can handle the execute).
>>>> >
>>>> > FYI: I added a mutability test into plc4j-api (which should
be added to plc4j-driver-bases after the refactoring) which tests all Items for mutability.
Currently we have some open issues regarding that.
>>>> >
>>>> > Sebastian
>>>> >
>>>> >> Am 12.09.2018 um 14:50 schrieb Andrey Skorikov
<[email protected]>:
>>>> >>
>>>> >> Hello,
>>>> >>
>>>> >> currently, PlcReadRequests and PlcWriteRequests are executed
by invoking the corresponding read/write operation on the PlcReader/PlcWriter objects. Hence the
typical workflow for reading a value contains the following steps:
>>>> >>
>>>> >> 1. Obtain a PlcReader instance from a PlcConnection
>>>> >> 2. Obtain a Builder by invoking readRequestBuilder() on
PlcReader
>>>> >> 3. Build a request using the Builder
>>>> >> 4. Execute the request by invoking read() on the PlcReader,
passing the constructed request as argument
>>>> >>
>>>> >> PlcReader reader = ... // obtain reader
>>>> >> PlcReadRequest request =
reader.readRequestBuilder().addItem(...).build();
>>>> >> Future<PlcReadResponse> response = reader.read(request);
>>>> >>
>>>> >> Since we only can build a request throgh a PlcReader
instance, invoking the read operation on the PlcReader is redundant. Therefore I suggest removing
the read/write operation from the PlcReader/PlcWriter and defining a execute() operation on
PlcRequest instead. The workflow would look like this then:
>>>> >>
>>>> >> PlcReader reader = ... // obtain reader
>>>> >> PlcReadRequest request =
reader.readRequestBuilder().addItem(...).build();
>>>> >> Future<PlcReadResponse> response = request.execute();
>>>> >>
>>>> >> Please note that there is no more need to "keep" a reference
to PlcReader in this context, since it is implicitly associated with the request by calling
reader.readRequestBuilder().build().
>>>> >>
>>>> >> Best regards,
>>>> >> Andrey
>>>> >>
>>>>
>>>>
>>>>
>
