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The support for invoking Business Tasks and Business Entity Methods through the RESTful interface is based on the requirements described in this article: RESTful services. Particularly the RestEntitiesWebHandler and the RestResourceService (as an Service a Service Instance of the IRestResourceService). 

Business Task methods and Business Entity methods are exposed as RESTful resources using the same set of annotations - and actually share a lot of similaritysimilarities. Business Entity invokable methods are typically PUBLIC VOID methods with a ProDataset INPUT-OUTPUT parameter and a (JSON serializable) parameter object. Business Task methods are typically PUBLIC VOID methods with zero to five ProDataset INPUT-OUTPUT parameters and a (JSON serializable) parameter object. 

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Due to limitations of the ABL reflection API, we currently do not support ProDatasets passed as the input to Business Task and Business Entity methods. This limitation has been accepted in our design process as we expect a majority of use-cases for RESTful invocation of Business Task and Business Entity methods just requires to return data in ProDatasets, not to receive data. So, the only input message to the invokable messages supported through the RESTful interface is the parameter object instance. 

As ABL reflection is not capable of providing the schema of the ProDataset parameters we've had to balance the requirement to provide the schema of the ProDataset parameters manually (through code in the Business Tasks) with the ease of use. The schema of ProDataset parameters is required as the loosely typed JSON messages do not allow the AVM to securely create an input ProDataset "on the fly" without losing schema compatibility with strong the strongly typed Dataset's used within Business Tasks and Business Entities. 

Preparing

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Business Tasks and Entities for RESTful invocation of methods

Business Tasks

A Business Task needs to implement the ISupportsRestMethods interface in order to support RESTful invocation. This Interface is expected by the IRestResourceService.

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RESTful interfaces for Business Entity methods are defined by an @RestMethod a @RestMethod annotations attached to the method (just before the METHOD block). 

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Every invokable methods method may be annotated with more than a single @RestMethod annotation to provide alternative URI's for the same method.

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1. For GET requests, the query string is first parsed and query string values will be used to populate the same named properties of the parameter object
2. For all other request methods, e.g. POST, the request entity (request payload) - when the request entity represents a JSON object - is used to deserialize a JSON serializable parameter object.
3. For all request methods (GET, POST, ...), the path parameter arguments are also assigned to properties of the parameter object. This is performed at the end, so that path parameters, as the strongest component of the request URI, overwrite properties assigned by query string components or deserialized form the request entity (request payload).  

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This annotation defines an endpoint for a Business Task method that will be exposed using a GET request under an URI llike like this:

http://localhost:8820/web/Entities/CalculateSumTask?Value1=17&Value2=4

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    @RestMethod (address="/GetCustomerAndInvoices", requestMethod="get",
                 parameterClassName="Consultingwerk.IntegerHolder",
                 response="poParameter,dsCustomer,dsInvoice").
    @RestMethod (address="/GetCustomerAndInvoices/~{Value}", requestMethod="get",
                 parameterClassName="Consultingwerk.IntegerHolder",
                 response="dsCustomer,dsInvoice").
    @RestMethod (address="/GetCustomerAndInvoices", requestMethod="post",
                 parameterClassName="Consultingwerk.IntegerHolder",
                 response="dsCustomer,dsInvoice").
    METHOD PUBLIC VOID GetCustomerAndInvoices (INPUT-OUTPUT DATASET dsCustomer,
                                               INPUT-OUTPUT DATASET dsInvoice,
                                               poParameter AS IntegerHolder):

This method allows clients to provide the Value property of the IntegerHolder parameter in one of the three ways:

GET http://localhost:8820/web/Entities/GetCustomerAndInvoices?Value=1

GET http://localhost:8820/web/Entities/GetCustomerAndInvoices/1

POST http://localhost:8820/web/Entities/GetCustomerAndInvoices with a JSON payload like: 

{ "Value": 2 }

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