When an external entity is used in an app module through the Data Hub pane, a consumed OData service document is added specifying the details of the consumed service. This is the API to the publishing app and the data associated with the entity.
2 Consumed OData Service screen
The Consumed OData Service document contains the following information:
Service name and the icon for the source application of the originating app
Version number of the consumed service
View in Data Hub Catalog link to the Service Details where you can see the full service details that are registered
Update/Switch – you can update the consumed service contract to another version that has been detected in Mendix Data Hub for the same app and service; the button will show the following, depending on what has been returned for the consumed contract in Data Hub:
Studio Pro will always show the Update option for the Consumed OData Service where you can check if an update is available. In the Data Hub search and App pane, when a different contract is detected at the service end-point, this will be indicated with an update arrow for the service. For further information on updating and switching services see the Updating or Switching a Consumed OData service section of this document.
- Update – this button is displayed so that you can Update the contract that is currently consumed (and shown in the Consumed OData Service document). You will be presented with the contract that is currently at the service end-point. It is good practice that only minor, non-breaking changes are deployed to the same end-point.
- Switch – this button is shown if other registered instances of the same service (with the same name, from the same app) are available in Data Hub and are deployed to different endpoints (for example, to another environment or because of changes that would break existing apps consuming the previous version)
In the Data Hub pane consumed services that have an available Update will have an update arrow to indicate this:
2.1 Connection Tab
The Connection tab displays the connection values for the consumed OData service:
2.2 Service URL
The Service URL displays the URL of the service endpoint:
- Click Select to select another constant for the service
Click Show to display the Constant dialog box displaying the service URL or endpoint:
Timeout is the response time for fetching the data from the service endpoint. If the endpoint has not responded after the number of seconds in Timeout (s), an exception will occur. If this happens during a microflow activity, the microflow will roll back or go into your custom error handling.
Default value: 300 seconds
2.4 Proxy Configuration
Proxy configuration allows you to configure whether to use a proxy for the request:
- Use app settings – use settings which are defined at the app level (default)
- Override – override the app-level settings for this action by specifying the host, port, user name, and password settings for the proxy
- No proxy – do not use a proxy for this service, even if there is a proxy configured at the app level
In most cases, this setting can be ignored, and the default Use app settings can be used.
The Use HTTP authentication check box specifies if basic authentication should be used. If checked, you have to specify the following details:
- User name – defines the user name that will be used for authentication
- Password – defines the password that will be used for authentication
Besides basic authentication, you can use custom authentication. For more information, see the HTTP Headers section below.
2.6 HTTP Headers
You can specify additional HTTP request headers to be passed to the endpoint in this list by clicking Add, Edit, or Delete for custom HTTP headers for authentication. Each custom header is a pair with a key and a value.
Using Headers from a Microflow, you can specify a microflow for creating a key and value pair(s) for dynamic values. The microflow must return a list of System.HttpHeader objects.
For more flexible HTTP request headers, you can select a microflow that returns a list of System.HttpHeader. This microflow may take a parameter of type System.HttpResponse. The microflow is called every time a request is made. Initially, the HTTP response parameter will be empty. If the response is 401 Unauthorized, the microflow is called with that HTTP response and another call is made with the new HTTP headers.
Custom authentication can be done with the microflow where the authentication value is retrieved (such as SSO). For further information on access and authentication, see Using Custom HTTP Header Validation for Published Entities in the Data Hub Guide.
3 Metadata Tab
In the Metadata tab, you can select a metadata file or use metadata obtained through a URL:
3.1 Metadata Editor
The metadata editor allows to open OData contracts from a file or URL. When you already consumed a contract, you can use this editor to update your existing contract with a new version from file or URL.
To open the Metadata Editor, click Edit. In the editor, you can specify a URL or file for the metadata:
The following settings are available:
- Import from – select URL or File for the location of the metadata:
- URL – click Edit to specify the URL for the metadata
- File – click Browse to select an XML metadata file
When downloading the metadata from a URL, the server may request a username and password (basic authentication). In that case, a dialog box will prompt you to enter your username and password. If the metadata file refers to other metadata files on the same server within the same realm, the username and password are re-used.
This information is not stored, so if you download the metadata from the same server again, you will have to enter your username and password again.
When you import the metadata, you can add external entities from the consumed OData service in the Data Hub Pane.
3.2 Consumed OData Service Properties
Click the Properties tab for the consumed OData service which displays the properties that were defined for the OData service document and the following additional properties:
- Entities – the URL of the metadata defining the entities and associated datasets
- Documentation – an additional description about this service for the current app
- Service name – the name of the published OData service that is consumed
- Service version – the version of the service that is consumed
- Service ID – the unique identifier of the service in the Data Hub Catalog
- Application ID – the unique identifier of the application that the service was published from in the Data Hub Catalog
- Metadata – the contents of the metadata file defining the service
- OData version – the OData version: can be OData 3 or OData 4
4 Updating or Switching a Consumed OData Service
4.1 Consuming from Service Endpoints
When you add an external entity to your app, you are consuming the entity from a specific version of a service (the service endpoint), deployed to a given environment. The metadata file or contract for the service is located at this endpoint.
The same service, deployed to a different environment will be to a different service endpoint and this will be registered as a different asset in the Data Hub Catalog. In the following example, there are three endpoints for the Sales 1.0.0 which is deployed to the production environment and the Acceptance and Test environments:
When you drag the Customer entity from CustomerApi version 1.0.0 deployed to the Acceptance environment into your app, Studio Pro will retrieve the information it requires from the contract that is at that endpoint.
4.2 Semantic Numbering for Service Versions
It is important that the publishers of the services adopt a strict revision process for any changes they make to their published OData services that are consumed by other users.
We recommend that a strict versioning system, for example semantic numbering, is used when issuing updates to services. The service version should clearly indicate the level and severity of the changes that have been made when a service is updated and deployed according to the following guidelines.
4.2.1 Minor Service Updates
Minor service updates are, for example, additional fields added to the service or new operations included which would not break any apps that consume the previous versions.
If semantic numbering is used then a minor/non-breaking change to a service can be indicated by an increase in the decimal part of the version number. For example, 1.0.11, 1.0.12, 1.1, 1.2.
Minor service updates can be deployed to the same service endpoints, thereby ensuring that all consuming apps consume the latest version of the service.
4.2.2 Major Service Updates
Major service updates are for example, when entities or attributes are removed, or input parameters are required, which would be incompatible for the consuming apps and result in the consuming app “breaking”.
When a major change has been made to a published service we recommend that the service is deployed to a different endpoint with the new service version number clearly indicating that there has been a major change—with semantic numbering this would be an incremental increase of a whole number.
In this case the new service should be registered in the Data Hub Catalog as a different service, and show up in the catalog as a separate asset. In the following example, there are 4 registered occurrences of the OrderManagementService:
There is a major service update indicated by the change in the version number from 1.0.0 to 2.0.0. Further, both major versions have also been deployed to Acceptance which also results in separately registered assets in the Data Hub Catalog at different endpoints.
Entities of non-Mendix OData services are identified with a key of one or more fields. If the key fields are changed in an update of the service, this will also be seen as a breaking change.
4.3 Update or Switch
When a change in the contract at a consumed endpoint is detected (possibly due to a minor change), or if the same named service is deployed with a major version number but to a different endpoint, the following options are available in the Consumed OData Service screen.
The Update option is available when Studio Pro detects that that the contract at the Catalog endpoint is different to the one currently consumed in the app. If the Update option is selected, the new contract will be loaded in the App.
188.8.131.52 App Pane and Data Hub Search Pane
In the App and the Data Hub Search Pane an update arrow will indicate if there is a different contract at the Catalog endpoint:
- The service version that is currently consumed is shown (in this example 1.0.0)
- Blue Update - click to open the Update Service box and update the contract to the new one. Studio Pro will retrieve the new contract at the Data Hub Catalog endpoint and this will be loaded in the app.
- The list of entities in this new version in the Data Hub are shown, including the locally consumed entities which are marked with a green check-mark. These entities are, however, greyed out to indicate that they cannot be dragged into the domain model as the contract for the previous version is currently being consumed. The only option is to click Update to retrieve the updated OData Service.
184.108.40.206 Update Service Dialog Box
When you click Update on the Consumed OData Service document or the update icon in the Data Hub and App sections, the Update dialog box is displayed.
The consumed OData service that is currently consumed in the app (1.0.0) is shown on the left, and you can click Update to retrieve the new contract from the Data Hub (2.0.0).
When an OData service is published to a different endpoint or to a different environment this will mean that it will be registered as a different asset in the Data Hub Catalog.
In the example given in the Consuming from Service Endpoints section above, if you are consuming the service from the Acceptance environment, the Consumed OData service screen will display the Switch button to enable you to consume the same service from the Production.
4.3.3 Switching Consumed Services
A published OData services that is deployed to multiple environments or is published with major service updates (and therefore deployed to a different endpoint) will be shown as separate items in the search results of the Data Hub pane.
In the following example, the consumed Orders version 1.0.0 deployed to Test environment is consumed in the app. However, the same service is deployed to the Acceptance environment:
To consume the service deployed to the Acceptance environment, follow these steps:
Click Update > Switch on the Consumed OData Service document:
On the Switch dialog box, from the drop-down list, select the service that you want to consume from (note that an endpoint is also detected that is deployed to Production) and click Switch:
The consumed service is be consumed from the new selected environment. The information on the Consumed OData Service document will display the changed service details and the Data Hub pane now displays that you are consuming from the selected environment: