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 > >> > > >
