Open Data Protocol (OData)

This article provides information about Open Data Protocol (OData) and explains how you can use OData V4 to expose updatable views.

What is OData?

OData is a standard protocol for creating and consuming data. The purpose of OData is to provide a protocol that is based on Representational State Transfer (REST) for create, read, update, and delete (CRUD) operations. OData applies web technologies such as HTTP and JavaScript Object Notation (JSON) to provide access to information from various programs. OData provides the following benefits:

• It lets developers interact with data by using RESTful web services.
• It provides a simple and uniform way to share data in a discoverable manner.
• It enables broad integration across products.
• It enables integration by using the HTTP protocol stack.

For more information about OData, see the following webpages.

The public OData service endpoint enables access to data in a consistent manner across a broad range of clients. To see a list of all the entities that are exposed, open the OData service root URL. The URL for the service root on your system has the following format: [Your organization's root URL]/data

Addressing

The following table describes the resources and the corresponding URLs in the Fleet Management sample.

OData services

We provide an OData REST endpoint. This endpoint exposes all the data entities that are marked as IsPublic in the Application Object Tree (AOT). It supports complete CRUD (create, retrieve, update, and delete) functionality that users can use to insert and retrieve data from the system. Detailed labs for this feature are on the LCS methodology.

Code examples for consuming OData services are available in the Microsoft Dynamics AX Integration GitHub repository.

Supported features from the OData specification

The following are the high-level features that are enabled for the OData service, per the OData specification.

• CRUD support is handled through HTTP verb support for POST, PATCH, PUT, and DELETE.

• Available query options are:

  • $filter
  • $count
  • $orderby
  • $skip
  • $top
  • $expand (only first-level expansion is supported)
  • $select

• The OData service supports serving driven paging with a maximum page size of 10,000.

For more information, see: OData actions that are bound to entities.

Filter details

There are built-in operators for $filter:

• Equals (eq)
• Not equals (ne)
• Greater than (gt)
• Greater than or equal (ge)
• Less than (lt)
• Less than or equal (le)
• And
• Or
• Not
• Addition (add)
• Subtraction (sub)
• Multiplication (mul)
• Division (div)
• Decimal division (divby)
• Modulo (mod)
• Precedence grouping ({ })

You can also use the Contains option with $filter requests. It has been implemented as a wildcard character. For example: http://host/service/EntitySet?$filter=StringField eq '*retail*'

The operators 'has' and 'in' are not supported.

For more information, see OData operators.

Batch requests

Batch requests are supported in the OData service. For more information, see OData batch requests.

Metadata annotations

/data/$metadata provides annotations. EnumType is support in $metadata.

Cross-company behavior

By default, OData returns only data that belongs to the user's default company. To see data from outside the user's default company, specify the ?cross-company=true query option. This option will return data from all companies that the user has access to.

Example: http://[baseURI\]/data/FleetCustomers?cross-company=true

To filter by a particular company that isn't your default company, use the following syntax:

http://[baseURI\]/data/FleetCustomers?$filter=dataAreaId eq 'usrt'&cross-company=true

Validate methods

The following table summarizes the validate methods that the OData stack calls implicitly on the corresponding data entity.

Exposing OData entities

OData entities are based on the concept of an updatable view. When the IsPublic property for an updatable view is set to TRUE, that view is exposed as a top-level OData entity.

Setting navigation properties between OData entities

Links between OData entities are described by a navigation property. Navigation properties describe the navigation from one end of an association to the other end.

Adding actions on OData entities

Actions let you inject behaviors into the data model. To add actions, add a method to the updatable view, and decorate that method with specific attributes. Here is an example.

[SysODataActionAttribute("CalcMaintenanceDuration", true)]
public int CalculateMaintenanceDuration()
{
    //do something
    return 0;
}

In this example, the SysODataActionAttribute class decorates the CalculateMaintenanceDuration method that is exposed as an action. The first argument of the attribute is the publicly exposed name of the action, and the second argument indicates whether this action is always available. Methods that are exposed as actions can return any primitive type or another public updatable view. After this method is exposed, it appears in the OData $metadata. Here is an example.

<Action Name="CalcMaintenanceDuration" IsBound="true">
    <Parameter Name="ViewMaintenance" Type="Microsoft.Dynamics.AX.Resources.ViewMaintenance"/>
    <ReturnType Type="Edm.String" />
</Action>

The following example of an OData action takes in a parameter and returns a list.

[SysODataActionAttribute("GetColors", true),
    SysODataCollectionAttribute("return", Types::Record, "CarColor")]
public List GetColorsByAvailability(boolean onlyAvailableVehicles)
{
    List returnList = new List(Types::Record);
    // do something
    return returnList;
}

In this example, the SysODataCollectionAttribute class enables OData to expose strongly typed collections from X++. This class takes in three parameters:

• The name of the parameter that is a list (Use return for the return value of the method.)
• The X++ type of the members of this list
• The public name of the OData resource that is contained in the collection

After these actions are exposed, they can be invoked from the service root URL.

You can find actions that are defined on data entities by searching for the SysODataActionAttribute attribute in the source code.

Querying or browsing an OData endpoint

OData enables an SQL-like language that lets you create rich queries against the database, so that the results include only the data items that you want. To create a query, append criteria to the resource path. For example, you can query the Customers entity collection by appending the following query options in your browser.

The OData protocol supports many similar filtering and querying options on entities. For the full set of query options, see Windows Communication Foundation.

Using Enums

Enums are under namespace Microsoft.Dynamics.DataEntities. Enums can be included in an OData query is by using the following syntax.

Microsoft.Dynamics.DataEntities.Gender'Unknown'

Microsoft.Dynamics.DataEntities.NoYes'Yes'

An example query for using the above enum values is shown below.

https://environment.cloud.onebox.dynamics.com/data/CustomersV3?\$filter=PersonGender eq Microsoft.Dynamics.DataEntities.Gender'Unknown'

https://environment.cloud.onebox.dynamics.com/data/Currencies?\$filter=ReferenceCurrencyForTriangulation eq Microsoft.Dynamics.DataEntities.NoYes'No'

The operations supported for enums are eq and ne.

Authentication

OData sits on the same authentication stack as the server. For more information about the authentication, see Service endpoints overview.

Tips and tricks

Run multiple requests in a single transaction

The OData batch framework uses changesets. Each changeset contains a list of requests that should be treated as single atomic unit. In other words, either all the requests are run successfully or, if any request fails, none of the requests are run successfully. The following example shows how to send a batch request that has a list of requests in a single changeset.

The SaveChangesOptions.BatchWithSingleChangeset option in SaveChanges() helps guarantee that all requests are bundled into a single changeset.

public static void CreateProductColors(Resources context)
{
    var productColorsCollection = new DataServiceCollection<ProductColor>(context);

    var color1 = new ProductColor();
    productColorsCollection.Add(color);
    color1.ColorId = "New Color1"; // set any other properties needed

    var color2 = new ProductColor();
    productColorsCollection.Add(color1);
    color2.ColorId = "New Color2"; // set any other properties needed

    context.SaveChanges(SaveChangesOptions.BatchWithSingleChangeset);
}

Prevent unset records from being posted when you use an OData client

When you create a new record by using an OData client, as shown in example 1, properties that aren't set are included in the body of the request, and default values are assigned to them. To prevent this behavior and post only properties that are set explicitly, use the SaveChangesOptions.PostOnlySetProperties option in SaveChanges(), as shown in example 2.

Example 1

public static void CreateVendor(Resources context)
{
    var vendorCollection = new DataServiceCollection<Vendor>(context);
    var vendor = new Vendor();
    vendorCollection.Add(vendor);
    // set properties
    context.SaveChanges();
}

Example 2

public static void CreateVendor(Resources context)
{
    var vendorCollection = new DataServiceCollection<Vendor>(context);
    var vendor = new Vendor();
    vendorCollection.Add(vendor);
    // set properties

    // Save specifying PostOnlySetProperties flag
    context.SaveChanges(SaveChangesOptions.PostOnlySetProperties);
}

Handling duplicate names between enums and entities in metadata

There are instances where enums and entities share the same name. This name duplication results in OData client code generation errors. To recover from this error, the helper code in GitHub can be used to identify duplicate name instances that must be removed. The generated metadata document can be used for further processing of the OData logic on the client side.

Array fields

OData does not support array fields in entities. This must be taken into consideration when designing entities that will be used with OData.

After restarting AOS, the first OData call may take a long time to process

The first OData call processed by an AOS that was restarted may take a long time to process because the metadata is not being cached. This latency can be avoided by warming up OData on AOS startup. For more details, see Build OData metadata cache when the AOS starts.