Andrea Magni

Hi @bioman, there are several approaches to the topic (CRUD operation against a DB). MARS doesn't dictate one specifically. Would you please specify if you are building a Delphi to Delphi solution (Delphi on the client and Delphi on the server)? You can have a dataset-oriented approach (client asks for a dataset, modifies it, changes are sent back to the server in form of delta updates) or a more general record-oriented approach (client asks for data, server sends a JSON array, client makes POST or PUT calls with modified/new data records). It also matters if you are looking for a data-centric approach (i.e. sending whole records from DB to client and back) or more interpolated approach (client commands REST server to perform operations that results in data manipulation). MARS is a lightweight library and I am trying not to dictate some aspects (more related to application than library IMO) so there are many ways to use it. Thanks for the kind words! Sincerely, Andrea

Hi, welcome to this forum and to MARS. I've worked in the past to some migration process from Datasnap to MARS (and from RemObjects to MARS too). One thing you could take advantage is that TMARSActivation class (quite the core of request / REST method execution matching) can be replaced / tweaked. This means you may change the way an http request is matched against the Delphi code to be executed to produce response. Or you may want to have a different strategy/parsing technology to fill REST method arguments from the request. Obviously this is not the easiest task in the world but may have a lot of sense especially on large projects (I've migrated large datasnap applications to MARS with minimal effort and reducing to the minimum changes in the methods code). Coming to your questions: 1) MARS can expose multiple engine (1 engine -> 1 port). Each engine can expose multiple applications. Each application can expose multiple resources. Each resource can expose multiple methods (http verbs and sub resources). You can organize resources as you like (one resource per unit, for example). I didn't get what you mean with "separate delphi project". You can deploy MARS server in several ways including ISAPI for IIS. 2) MARS serialization/deserialization mechanisms are designed to be pluggable so you can implement your own readers/writers to handle OleVariants as you prefer. 3) I have knowledge of MARS servers used in heavy load situations. Numbers are not significative because they actually depends on hardware/storage/purpose of REST methods. If you are looking for extreme performance, I would take a look to mORMot. But in 99% of my experience MARS is fast enough and REST architecture may help you to properly deal with scaling and performance boosts. Sincerely, Andrea

Hi, thanks for the kind words and sorry for the delay. I guess you are referring to QueryParam like "sort" in http://localhost:8080/rest/default/query/EMPLOYEE?sort=LAST_NAME You can use the Required attribute to let MARS check for the parameter's existence before calling the REST method. function GetDataset([QueryParam, Required] sort: string): TFDQuery; I would add a specific value in the user's token, indicating the DB to use. You'll set this value in the token at authentication time (via API key or regular login). You can see this thread for a similar approach: Keep in mind that your situation (if you store the connection name to be used inside the user's token) it's easier as you can use a connection name like 'TOKEN_CLAIM_DBCONNECTION': [Context, Connection('TOKEN_CLAIM_DBCONNECTION', True)] FD: TMARSFireDAC; And MARS will expand that connection name to the value of the DBCONNECTION name stored in the Claims of your (JWT) token. If you need some fallback mechanisms or more dynamic behavior, follow the instructions in the "FireDAC Connections" thread I linked here above. Feel free to ask whatever you need, sorry for the delay in this reply but I am abroad with family (vacation time). Sincerely, Andrea

Hi @Rafael Mattos, MARS supports JsonDataObjects but does not include them (I am thinking about changing this...). You simply need to download JsonDataObjects (https://github.com/ahausladen/JsonDataObjects) and setup your library path to compile it. Then MARS' demo should work. Let me know please. Sincerely, Andrea

It turned out it was the wildcard in the Accept header to cause this. I just pushed a fix that should also apply to your case and you may no longer need to instruct the Accept header all the times. Branch: develop, link to the commit: https://github.com/andrea-magni/MARS/commit/b8d5768b65072ff403de3c60e17688e8e95b1d9a Sincerely, Andrea

Hi @Stuart Clennett, you can add the IsReference attribute to instruct MARS not to free the object returned by the method (as it will be destroyed within the datamodule of course, as it is its owner). [GET/POST, IsReference] function GetAssessment(const id: string): TFDDataSet; Sincerely, Andrea

Hi @Stuart Clennett, I am happy you found a way to solve by yourself while I was in vacation 🙂 Your solution works but has a couple of things to consider: 1) that BeforeHandleRequest code gets executed for each incoming request (performance) 2) manipulating Parameters is not suggested as App.Parameters is like a global object (IIRC). You have an other opportunity through (yet another) undocumented MARS feature: [Context, Connection('Dynamic_MyConnection', True)] FD: TMARSFireDAC; The Connection attribute specifies the name of the connection definition to be used with the TMARSFireDAC instance injected. The name supports macros (the second argument enables macro expansion). You can rely on built-in macros (i.e. using some part of the token, params, username or similar things. A list is available here: https://github.com/andrea-magni/MARS/blob/a8d323558bd591589ef667eac326324302d167a9/Source/MARS.Data.FireDAC.pas#L528 ). Last chance of the macro-expander is looking for custom providers. You can register your own in the initialization of one of your units or in the Server.Ignition.pas file: TMARSFireDAC.AddContextValueProvider( procedure (const AActivation: IMARSActivation; const AName: string; const ADesiredType: TFieldType; out AValue: TValue) begin if SameText(AName, 'Dynamic_MyConnection') then begin if Odd(SecondOf(Now))then AValue := 'OddConnection_' + AActivation.Request.HostName else AValue := 'EvenConnection_' + AActivation.Request.HostName; end; end ); Beware: the connection name has to be this format: [PREFIX]_[SUFFIX](_[OTHER_SUFFIX]) Using 'MyConnection' won't work for instance... Pros of this approach: 1) code is executed only when needed (when the TMARSFireDAC instance gets created to be injected in your resources), all others REST endpoints won't be affected. 2) it seems more isolated to me (but this can be a personal evaluation). If you need to fix some TFDConnection instances on your datamodules, try having a TMARSFireDAC instance injected in the datamodule itself and use the FD.ConnectionDefName (already expanded once injected) to fix the ConnectionDefName of your components (OnCreate event of the datamodule should be fine, or AfterConstruction method as well). If you encounter troubles doing this, write here again: there's another hidden feature for you to fix this (when registering the datamodule as resource you can specify an anonymous method to initialize it or to call a custom constructor instead of TDatamodule.Create(AOwner)). Sincerely, Andrea

Hi @Yaron, you can register an InvokeError procedure to deal with non-matching URLs, there's a template in Server.Ignition file, line 107 (https://github.com/andrea-magni/MARS/blob/daef64912b04036917cb336c4eee34438fa993a8/Demos/MARSTemplate/Server.Ignition.pas#L107). If you uncomment that registration, you can implement whatever policy using the AActivation argument to access Request and Response objects (you can set the StatusCode, Content and ContentType of the Response object as you like). Sincerely, Andrea

I'm about to release TFormStand as a form-oriented twin of TFrameStand. To add support for TForm I had to refactor quite heavily TFrameStand code (now there is a common ancestor that is TSubjectStand and two inherited components TFrameStand and TFormStand). I am looking for: - people willing to test TFrameStand functionalities (regression tests) are still functioning; - people willing to test TFormStand Please reply to this message or contact me directly if you like to be involved. The new version is available in the TSubjectStand branch of TFrameStand GitHub repository: https://github.com/andrea-magni/TFrameStand/tree/TSubjectStand (Beware: uninstall any previous version of TFrameStand before installing the new one) Thanks Sincerely, Andrea

Unfortunately not... The TFrameStand functionalities should be the same, there are some changes due to refactoring (i.e. if you had event handlers for TFrameStand events, some argument changed type like TFrameInfo<TFrame> now being TSubjecTInfo, so you may need to adjust them on your side). TFormStand is the same concept but supporting TForm instead of TFrame. If you already have projects using TFrameStand, it would be helpful if you could confirm I broke nothing. Sincerely, Andrea

Hi, yes the HTML form should be a multipart/form-data one... Glad you solved 😉 Sincerely, Andrea

Great, please check out the new version from https://github.com/andrea-magni/TFrameStand/tree/TSubjectStand (you can use Git or download a zip file if you are not confident with Git). Just beware to uninstall any previous version of TFrameStand before proceeding. Some changes in your code may be needed especially if you used TFrameStand events. For example where you had TFrameInfo<TFrame> as event handler argument, now you'll find TSubjectInfo (that is a new superclass of TFrameInfo<T>). If you encounter issues, just drop me a line. Thanks. Sincerely, Andrea

Thanks, I relocated the blog some time ago and I set up a rewrite rule that for some reason is not working well. I changed the links and updated also the demo list. That document will change again soon however, I'll add section for TFormStand soon. Sincerely, Andrea

Hi @Yaron, you can definitely get rid of the "/rest" prefix by setting the Engine BasePath property to empty string (by default the engine has 'DefaultEngine' as Name and '/rest/ as BasePath): class constructor TServerEngine.CreateEngine; begin FEngine := TMARSEngine.Create; try // Engine configuration FEngine.BasePath := ''; // <============== FEngine.Parameters.LoadFromIniFile; // Application configuration FEngine.AddApplication('DefaultApp', '/default', [ 'Server.Resources.*']); If you want to push this thing futher, you can even think about inheriting your own TMARSActivation class and shortcut request matching by overriding FindMethodToInvoke method. HTH Sincerely, Andrea

Sorry, it's my fault: MARS supports two http layer implementor on the client side: Indy and TNetHttpClient. Handling errors has some differences across the two, so it depends if you are using a TMARSClient (Indy) or TMARSNetClient (TNetHttpClient). Either ways, you can define an OnError handler for your TMARSApplication: uses FMX.Dialogs , MARS.Core.Utils, MARS.Client.Utils , IdHttp; var LException: EMARSClientHttpException; LIdException: EIdHTTPProtocolException; begin if AException is EMARSClientHttpException then begin LException := EMARSClientHttpException(AException); ShowMEssage('Error' + LException.Message + ' Details: ' + StreamToString(LException.Content)); AHandled := True; end; if AException is EIdHttpProtocolException then begin LIdException := EIdHttpProtocolException(AException); ShowMEssage('Error' + LIdException.Message); AHandled := True; end; end; IIRC I was not able to find a way to collect error details (that are sent back from the server to the client using the body of the response) when using Indy. I am open to discuss how to improve the overall mechanism, please express your thoughts (everybody!). I'll try to update the old demos (such as HelloWorld) to include error handling at some point. Sincerely, Andrea

Change TDataSet to TFDDataSet and you'll be able to produce both TMediaType.APPLICATION_JSON and TMediaType.APPLICATION_JSON_FireDAC (MARS will match what client prefer, looking for the Accept header's value): [POST] function GetData([BodyParam] AStatement: TStatement): TFDDataSet; function THelloWorldResource.GetData(AStatement: TStatement): TFDDataSet; begin Result := FD.SetName<TFDDataSet>(FD.Query(AStatement.SQL), AStatement.Name); end; Beware to remove the explicit Produces attribute you had. You may want to use a REST debugger (I like Postman) to make a call using Accept: application/json-firedac or Accept: application/json to see the two serializations. Now you can add a TMARSClientResourceJSON to your client application, note the SpecificAccept header where I am instructing to set Accept header to application/json-firedac media type: object MARSClientResourceJSON1: TMARSClientResourceJSON Application = MARSApplication SpecificAccept = 'application/json-firedac' SpecificContentType = 'application/json' Resource = 'helloworld' end Then use the following code (TMainDataModule is a datamodule containing the REST components, TMARSClient, TMARSApplication, TMARSClientResourceJSON): uses MARS.Core.JSON, MARS.Core.Utils, MARS.Data.FireDAC.Utils; procedure TMainDataModule.RetrieveData(const ASQL, AName: string; const AOnCompleted: TProc<TFDMemTable>; const AOnError: TProc<Exception> = nil); begin MARSClientResourceJSON1.POSTAsync( procedure (ABody: TMemoryStream) var LJSON: TJSONObject; begin LJSON := TJSONObject.Create; try LJSON.WriteStringValue('SQL', ASQL); LJSON.WriteStringValue('name', AName); JSONValueToStream(LJSON, ABody); finally LJSON.Free; end; end , procedure (ARes: TMARSClientCustomResource) var LData: TArray<TFDMemTable>; begin LData := TFDDataSets.FromJSON((ARes as TMARSClientResourceJSON).Response as TJSONObject); try if (Length(LData)>0) and Assigned(AOnCompleted) then AOnCompleted(LData[0]); finally TFDDataSets.FreeAll(LData); end; end , AOnError ); end; Then you can have a call like: MainDataModule.RetrieveData('select * from EMPLOYEE', 'Employee' , procedure (ADataSet: TFDMemTable) begin FDMemTable1.Data := ADataSet.Data; // cloning dataset end , procedure (AError: Exception) begin ShowMessage(AError.ToString); end ); FDMemTable1 is a TFDMemTable to store data on the client side. Please consider: 1) code could have been more simple than this but I wanted to include the fact this call is actually made asynchronously (so if you need to transfer a large dataset or connection is not very fast, you are not going to hang your client application); 2) this is a good example how to retrieve a dataset and then have a single (synchronized) point where the resulting dataset is then cloned to a local TFDMemTable that can be easily involved in databinding (LiveBindings) without being affected by the async call. Please let me know if this helps. Sincerely, Andrea

TMARSFDResource is tightly coupled with a server side resource that has this interface: [GET, IsReference] function Retrieve: TArray<TFDDataSet>; [POST] function Update([BodyParam] const ADeltas: TArray<TFDMemTable>): TArray<TMARSFDApplyUpdatesRes>; One example of such resource is TMARSFDDataModuleResource (MARS.Data.FireDAC.DataModule.pas) that is the base class of the datamodule in FireDAC Basic demo. The logic of this resource does not allow the client to push statements to server (the Retrieve method is marked with GET verb so you don't have body available to send statements to be executed to sever side). Also, the Update method needs to know the structure (statements) of dataset in order to proprerly apply deltas to them. You can build a different resource on the same idea but adding statements as input to both methods. The Retrieve part we already covered in the previous message (using POST verb). You may want to have a PUT verb to apply updates. On the client side, you can use a TMARSClientResourceJSON and the TFDDataSets utility class (MARS.Data.FireDAC.Utils unit) to manage persistence of an array of datasets and/or an array of deltas (have a look at MARS.Client.FireDAC unit for some examples). As said, it is a bit unusual to send statements to be executed from the client to the server so there's no specific integration in MARS for this. It should not be hard to implement and all building blocks are already there. However if you find difficulties just write on this forum and I'll be happy to help. Sincerely, Andrea

Hi @Michal S., for security reasons, I decided to avoid error messaging to automatically flow to the client. Error messages may contain sensitive data and by default MARS reply with an 'Internal Server Error' message if an Exception is raised in the server code. However: 1) for debug purposes, you can switch the Build Configuration from Release to Debug and have the error message appended after the Internal Server Error string. 2) in real code, if you want the message to flow to the client use a EMARSHttpException object: function THelloWorldResource.MyMethodWithException: TJSONObject; begin Result := TJSONObject.Create; try Result.WriteStringValue('msg', 'This method will raise an exception'); // raise Exception.Create('This is my custom error message'); // this will be seen as 'Internal server error' raise EMARSHttpException.Create('This is my custom error message'); // this message will flow to the client except Result.Free; raise; end; end; HTH. Sincerely, Andrea

Hi @Yaron, if you are using MARS develop branch, you can do as the following example: uses MARS.Core.RequestAndResponse.Interfaces THelloWorldResource = class //... protected [Context] Response: IMARSResponse; public [GET, Path('cookietest')] function MyMethod(): TJSONObject; end; function THelloWorldResource.MyMethod: TJSONObject; begin Result := TJSONObject.Create; Result.WriteStringValue('msg', 'This method will also set MyCookie value to current time'); Response.SetCookie('MyCookie', TimeToStr(Now), 'localhost', '/', Now+1, True); end; If you are using MARS master branch, it should be very similar but you need to use TMARSResponse instead of IMARSResponse (and the MARS.Core.RequestAndResponse.Interfaces unit is not available). But the SetCookie method call should be the same. This example sets the MyCookie value to the current time (string) for 'localhost' domain (you may want to read the actual host from the incoming request) and for every path matching '/'. Expiration is set 1 day after the request and the Secure flag is set to True. Sincerely, Andrea

@Arnaud Bouchez great to see you chiming in here :-) @ertank I agree with Arnaud that having the client sending the SQL statements to be executed on the server is basically breaking the separation between layers in the multi-tier system and this has consequences (changes in client and/or db structure are probably deeply tied). It is easy though to implement what you are asking for: 1) find a way to send SQL statements to the server (I would probably use a JSON structure in the body of a POST request) 2) grab the list (or the single) of SQL statements from the body 3) build an array of corresponding datasets 4) return that array to the client Extra: if you need to modify data and you are building a Delphi-To-Delphi system (Delphi client, Delphi server), you can even consider then posting back delta changes to the server and have these applied as in a C/S scenario (MARS has FireDAC integration for this task, just ask if it's your case). Simple example: 0) bootstrap a new MARS server application (using MARSCmd) or use an existing one 1) include these units: Data.DB, MARS.Data.FireDAC, FireDAC.Phys.FB (or whatever physical driver is needed for your DB) 2) define data structures: TStatement = record SQL: string; name: string; end; TStatements = TArray<TStatement>; 3) define a POST method having TStatements as input and an array of datasets as output: [Path('helloworld')] THelloWorldResource = class protected [Context] FD: TMARSFireDAC; public [POST, Path('data'), Produces(TMediaType.APPLICATION_JSON)] function GetData([BodyParam] AStatements: TStatements): TArray<TDataSet>; end; implement it: function THelloWorldResource.GetData(AStatements: TStatements): TArray<TDataSet>; var LStatement: TStatement; begin Result := []; for LStatement in AStatements do Result := Result + [ FD.SetName<TDataSet>(FD.Query(LStatement.SQL), LStatement.name) ]; end; 4) make the POST call from the client side (using MARS Client or whatever other http library available): POST /rest/default/helloworld/data HTTP/1.1 Host: localhost:8080 Accept: application/json Content-Type: application/json Host: localhost:8080 [ { "SQL": "select * from EMPLOYEE order by EMP_NO", "name": "Employees" } , { "SQL": "select * from COUNTRY where COUNTRY like 'I%'", "name": "Country" } ] 5) this is what the server response will look like: { "Employees": [ { "EMP_NO": 2, "FIRST_NAME": "Robert", "LAST_NAME": "Nelson", "PHONE_EXT": "250", "HIRE_DATE": "1988-12-28T00:00:00.000+01:00", "DEPT_NO": "600", "JOB_CODE": "VP", "JOB_GRADE": 2, "JOB_COUNTRY": "USA", "SALARY": 105900, "FULL_NAME": "Nelson, Robert" }, { "EMP_NO": 4, "FIRST_NAME": "Robert", "LAST_NAME": "Vecchio", "PHONE_EXT": "233", "HIRE_DATE": "1988-12-28T00:00:00.000+01:00", "DEPT_NO": "621", "JOB_CODE": "Eng", "JOB_GRADE": 2, "JOB_COUNTRY": "USA", "SALARY": 97500, "FULL_NAME": "Vecchio, Robert" } ], "Country": [ { "COUNTRY": "Italy", "CURRENCY": "Lira" } ] } To materialize back data into datasets on the client side you can use several strategies (including the Delphi REST Client library TRESTResponseDataSetAdapter, either using REST Client library components or MARS Client library components to perform the request). If you are using FireDAC on the client side and you can afford relying on having the same FireDAC version on client and server, consider also using the TMARSFDResource component (see MARS' FireDAC Basic demo). Sincerely, Andrea

Hi @ertank, latest stable version is 1.3.2 (that currently is even with master branch). The develop branch is where development occurs and is a hundred commits ahead of the master branch currently. I would suggest you to use 1.3.2 in production and eventually check this page: https://github.com/andrea-magni/MARS/releases to see if it is still the latest from time to time. You also have there a kind-of what's changed information. If you are looking for latest features, then develop branch is there for you but beware things may change unexpectedly and bugs may be there. Sincerely, Andrea

Hi @Yaron, web applications may authenticate following several different schemas. One of them is handling authentication and authorization through a token (Authentication Bearer schema) that for convenience may also be embedded into requests through the use of a cookie. This kind of authorization/authentication schema is built-in with MARS and relies on JWT (https://jwt.io/) technology. This means I've made some work to integrate JWT in MARS and it is provided as an example of authentication/authorization mechanism but it does not mean it is mandatory to use it, you can consider it as a working example. It is also production-ready BTW. The typical use case: 1) the client (JS or whatever) should get a token from the server (make a POST request to the included TTokenResource class) 2) store the token somewhere on the client-side (or rely on the cookie that the server instructs to keep when successful authentication is done) 3) endorse the token within each client request through the Authentication header ("Bearer <TOKEN>") or rely on browser sending the cookie back to the server On the server side, you may ask MARS to provide you an instance of TMARSToken through the Dependency Injection mechanism built-in with MARS. Just add a "[Context] TheToken: TMARSToken;" field to your resource class and you'll get a valid instance (check TheToken.Verified, TheToken.UserName and other properties). Also check the Authentication demo and try to open a browser at the following URL: http://localhost:8080/rest/default/token/html You can use Chrome Developer Tools to see requests and cookies. Let me know if this helps, otherwise I may add a demo of a simple webapp using Bootstrap and performing authentication. Sincerely, Andrea

Hi @Rafael Mattos, MARS server applications can be deployed in several ways. You can go for the ones relying on Webbroker (standalone indy server) and configure SSL there. Otherwise you can go for apache module/iis ISAPI and let the web server handle encryption. Last, if you are brave enough, you may try new Delphi Cross Socket integration (develop branch) and have SSL implemented that way. I tend to leave the REST server http only and ads a reverse-proxy apache instance in front of it, implementing https there (easy, well documented, reliable). Sincerely, Andrea

Glad you worked around this. I believe (I need to replicate this and investigate a bit) the Accept header sent from Angular matches also some MARS XML serializer. Will let you know here as soon as I figure out what's happening. Thanks! Andrea

Do you have a chance to debug the server (run the server application with the debugger)? Or at least recompile the server in Debug configuration (that should give us some more error details, more than "Internal server error"). I think the problem may be that Accept value... Sincerely, Andrea