I am trying to create a OData service that returns user parameters found in the databasde usr05. Those can be accessed by the ABAP statement:
GET PARAMETER ID 'XXX' FIELD YYY.
This means, that basically do not need a key value.
In SEGW it is impossible to create an entity type without one though.
The solution of course could be a dummy key field, that is simply ignored in the backend implementation.
Does anyone know a better solution?
Thanks in advance,
Eric
it is not a shame it is by design and follows the OData specification.
Every entity type must have a key.
What you can try to use instead is to use a property that is based on a so called complex type within an entity type that is used for your users.
The latter should have a key.
Like the complex type address that is used in the entity type Supplier
https://services.odata.org/OData/OData.svc/$metadata
Related
I am working on a patch for a firebird rails adapter. My goal is to make it possible to define a column as the type boolean if the domain of the column has a defined name.
I found the SqlTypeMetadata class which I am using to create FirebirdColumns in the method fetch_type_metadata in the module SchemaStatements.
But it seems that this is used only after the data is fetched so it doesn't use the defined true/false values in the query. So, right now, I am looking for a way to tell ActiveRecord the type of a column on an adapter basis. I read the files schema_definitions and schema_statements several times in case I am missing something but I couldn't find a method there... .
Where is a method that I can overwrite to make the typecasting correct?
Firebird doesn't communicate information about the domain of a column in the bind information of a prepared query. It only communicates the basic underlying datatype information. So if you have defined a domain X with underlying type CHAR(1), then Firebird will communicate it as a CHAR(1), not as X.
There is no option to obtain the domain, except by querying the metadata tables for additional information. So, what you want to achieve is either not possible, or at least it will be complicated.
I'm currently working on a OData Service(SAP Gateway), wherein the entity types are generated during the runtime. I know, that this wouldn't be as per the OData best practices, where the entity types should be static and is part of the design phase.
Questions:
1. With the request for metadata, all the entity types are generated in a method called DEFINE(provided by SAP Gateway framework). I'd like to separate the generation of each entity type, as the information required for the generation is different for each entity type. Later on, new entity types will be added, which would have a further set of instructions for the generation.
Is the Strategy pattern best for this? With this, the generation of different entity types are separated. If Strategy, then, should the Factory method return all the concrete strategies at once and let the context loop through all the strategies to generate the entity types?
Or is there any other design approach for this?
Thanks a lot in advance!
The entity types are defined in method DEFINE. The definition is nothing but creation of entity type based on a defined data structure. The code required to create entity types varies for each entity type. With runtime, I mean, the code written as the definition of entity type, is executed to form an entity type during the request for metada.
I would like to extend the types generated by the LinqToSQL TypeProvider with additional members. Is this possible? For example if the TypeProvider is pointed to a DB with a table called Company it will expose a type Company with access to the columns. As an example can I a member Company.employees to the generated type which will return all current employees from the employees table?
I don't see why you could not.. provided you have the source for the type provider!
That said, creating or extending a type provider, while not being overly complicated, is not trivial either.
So depending on how central this type generation aspect is for you, it might be best to use existing type providers, and build a layer on top of them on the 'client side'.
Once you have refined a compelling scenario where this would really yield value, then you can reuse this layer anyway.
What is your end-scenario ?
Doesn't the existing SQL Type provider cover the Company.employees case ?
It sounds like what you want to do could be accomplished by using a type extension.
Type extensions can be added to any accessible type, which should include types generated by the type provider.
In my database User table I have DataTime field called DateDeleted - which is null while user exists and is set to the proper value when user "is deleted".
I wonder if there is a way to introduce IsDeleted property for User entity so that
http://odata/service.svc/Users(1)/IsDeleted
will return true or false depending on whether DateDeleted is set or not
My research in google hasn't got any results and I am almost sure it is not possible to implement through odata. Am I right?
With the built in providers this is not possible on the WCF DS side of things. You might be able to somehow do this on the EF side (expose it as a property of the EF entity), but I'm not sure if that's possible.
On the WCF DS side, you would have to implement a custom provider in order to do this. Which may be quite a lot of work unfortunately. If you're interested see this for starters: http://blogs.msdn.com/b/alexj/archive/2010/01/07/data-service-providers-getting-started.aspx.
What Shawn refers to above is a method on the custom provider interface.
You can specify the value you want by implementing the method DataServiceQueryProvider.GetPropertyValue.
Please find the reference here:
http://msdn.microsoft.com/en-us/library/system.data.services.providers.idataservicequeryprovider.getpropertyvalue.aspx
The method takes two parameters, the entity object (a User instance) and the resource property (in this case "IsDeleted"). You can try to get the property value of "DataDeleted" from the entity object, and return the value of "IsDeleted" as you want.
I have an Entity-class having a Property of type Int32: on generating DDL using DevArt for ORACLE a NUMBER(10) column is generated. Reading and writing instances works flawlessly.
However, on fetching instances of this Entity-class sending a custom query to ExecuteStoreQuery on the ObjectContext this Property seems to be returned as System.Double, as such constructing the instances fails.
Can I hint DevArt to construct System.Int32?
Thank you.
Bart
The reason is the fact that OracleDataReader, which is used in the ExecuteStoreQuery method, has type mapping different from the one used in the Entity Framework provider.
I recommend you to use NumberMappings, I suppose you will need to map Number(10) to Int32: Number Mappings=((NUMBER,10,10,System.Int32). These changes should be persisted to the model connection string (they are duplicating the default EF mapping rules, it is necessary for the OracleDataReader from ExecuteStoreQuery).
Please let us know if the problem persists.