Support for RESTful invocation of Business Task and Business Entity Methods
- Mike Fechner
- Peter Judge
- Martyn Kemp
Introduction
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 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 similarities. 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.
Support for return value of Business Task and Business Entity Methods
Also to facilitate the support for RESTful invocation of Business Task and Business Entity methods the Consultingwerk.OERA.ServiceInterface:InvokeTask API has been enhanced with support for returning the return value of a method to the caller. This finally allows developers to separate the request message from the response message.
The InvokeTask API is fully capable of invoking Business Entity methods as well.
Known limitations
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 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 the strongly typed Dataset's used within Business Tasks and Business Entities.
Preparing 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.
CLASS Consultingwerk.SmartComponentsDemo.OERA.SampleBusinessTask
IMPLEMENTS IBusinessService, ISupportsRestMethods:A typical implementation of the required GetRestMethods method looks like this:
/**
* Purpose: Returns the list of supported rest adresses for methods
* to the caller
* Notes:
* @return The list of supported rest methods to the caller
*/
METHOD PUBLIC ListRestMethod GetRestMethods ():
RETURN (NEW RestMethodProvider():GetRestMethods (THIS-OBJECT:GetClass())) .
END METHOD .Business Entities
Business Entities implement the GetRestMethods method by inheriting from the Consultingwerk.OERA.BusinessEntity class. It is however still required to declare the Interface in the Business Entity class header:
CLASS Consultingwerk.SmartComponentsDemo.OERA.Sports2000.CustomerBusinessEntity
INHERITS SmartBusinessEntity IMPLEMENTS IFetchDataByReference, ISupportsRestAddress, ISupportsRestMethods:Invokable methods
Valid signatures for methods that can be invoked using the RESTful interface must have the following characteristics:
Zero to five INPUT-OUTPUT datasets or dataset handles.
Zero or one INPUT parameter object. If used, the parameter object must be the last parameter defined.
A void return value, or an OOABL type that is serializable to JSON (typically using the Consultingwerk.IJsonSerializable interface).
This includes methods that take no inputs and return no values, as well as methods that have only a single dataset INPUT-OUTPUT parameter.
Defining RESTful interfaces for invokable methods
RESTful interfaces for Business Entity methods are defined by a @RestMethod annotations attached to the method (just before the METHOD block).
Arguments of the @RestMethod annotation
The annotation provides the following arguments:
Argument/Attribute | Mandatory | Description |
|---|---|---|
address | no | The URI pattern to invoke the method. When not specified the pattern /{methodName} is used by default |
ParameterClassName | no | The name of the parameter class to instantiate for calling into the method. When not specified, the OOABL type name of the parameter is used. In either case, if the type name is not instantiable - if it's an interface, enum or abstract class - then a Consultingwerk.Exceptions.InvalidValueException will be raised. |
RequestMethod | no | The http method for the call described by this annotation. When not specified, get will be assumed as the default. |
Request | no | Comma delimited list of the components from the JSON request body of the REST request. Components are "parameter" and the names of the ProDataset parameters. |
Response | yes | Comma delimited list of the components for the JSON response of the REST request. Components are "return", the names of the ProDataset parameters and the name of the parameter. If only a single ProDataset is provided, it may have additional modifiers.
|
mapHeaders | no | Comma-delimited list of HTTP header names that are set as values on the method parameter object.. The header names may have an optional mapped property name, delimited by =. For example, a value of Accept-Language=Language,Content-Disposition sets the values of the Accept-Language and Content-Disposition headers from the web request to properties named Language and Content-Disposition. |
mapCookies | no | Comma-delimited list of HTTP cookie names to be set as values on the method parameter object. The cookie names may have an optional mapped property name, similar to the mapHeaders value. For example, a value of JSESSIONID=SessionId will set the value of the JSESSIONID cookie to a property named SessionId on the parameter object. |
tags | no | Comma-separated list of tags used for grouping endpoints in Swagger documentation. |
requestParameterSchemaType | no | An alternate name to use for the (input) parameter class in the Swagger documentation. This allows details of the implementation to be hidden. If not provided, the parameter's OOABL class name is used. |
responseSchemaType | no | An alternate name to use for the return value class in the Swagger documentation. This allows details of the implementation to be hidden. If not provided, the OOABL type name of the return value is used. |
propertyFrom | no | Comma-delimited list of values indicating how property values for a parameter class should be provided. Each entry has the format <property-name>:[query|hidden] . A value of query indicates that a query string is used. A value of hidden indicates that a value for that property is not expected to be sent by a client. |
description | no | A description for the operation used in the Swagger documentation |
Every invokable method may be annotated with more than a single @RestMethod annotation to provide alternative URI's for the same method.
Arguments of the @ParameterSchema annotation
When Business Task methods are configured to return a Dataset as the method response, it's required to provide an XSD file with the ProDataset schema to be included in the method documentation, e.g.:
Argument/Attribute |
|---|