How can I use the OData4 service in Java using Olingo or SDL OData Framework

Question

I need to use the OData4 service from Java and based on the list of frameworks on the OData website , two options: Olingo or SDL Odata Framework . My problem is that the documentation for both of these projects is focused on writing a service that does not consume it. The Olingo site is linking to a blog post from 2014 that does not support the API with the current version, and I could not find anything on the github SDL pages.

If someone could just provide me with a simple POST / GET example using a suitable POJO object model, which would be great.

My limited understanding is that OData moves any information about the actual object model from compile time to the client runtime. I gladly ignore this and encode with a fixed object model, because the service we use will not change.

Answer 1

Client-side API documentation seems to be ignored by Olingo. But in the sample / client there is an example in the GIT repository .

Basically for GET you do the following:

String serviceUrl = "http://localhost:9080/odata-server-sample/cars.svc" String entitySetName = "Manufacturers"; ODataClient client = ODataClientFactory.getClient(); URI absoluteUri = client.newURIBuilder(serviceUri).appendEntitySetSegment(entitySetName).build(); ODataEntitySetIteratorRequest<ClientEntitySet, ClientEntity> request = client.getRetrieveRequestFactory().getEntitySetIteratorRequest(absoluteUri); // odata4 sample/server limitation not handling metadata=full request.setAccept("application/json;odata.metadata=minimal"); ODataRetrieveResponse<ClientEntitySetIterator<ClientEntitySet, ClientEntity>> response = request.execute(); ClientEntitySetIterator<ClientEntitySet, ClientEntity> iterator = response.getBody(); while (iterator.hasNext()) { ClientEntity ce = iterator.next(); System.out.println("Manufacturer name: " + ce.getProperty("Name").getPrimitiveValue()); } 

Take a look at the sample in the Olingo code base for more information on how to get metadata, handle all properties, etc.

To do a POST, you can do the following. (Note that this is not verified code, and the Car service sample is read-only.) First, you create the data as ClientEntity. You for example with

 ClientComplexValue manufacturer = of.newComplexValue("Manufacturer"); manufacturer.add(of.newPrimitiveProperty("Name", of.newPrimitiveValueBuilder().buildString("Ford"))); 

Then you send a POST request

 ODataEntityCreateRequest<ClientEntity> request = client.getCUDRequestFactory().getEntityCreateRequest(absoluteUri, manufacturer); ODataEntityCreateResponse<ClientEntity> response = request.execute(); 

So this is not with POJO classes - the result type is ClientEntity, which represents the data as name / value maps. There is already another unresolved question about this specific topic in Olingo - the creation of strongly typed POJOs for the OData client service library and I suggest that we go there to follow up on this.

Answer 2

For the SDL OData framework, you can check out this Github Test class on how to use the OData client.

The OData SDL structure is based on EDM classes and a simple example for getting all products (Product Edm Entity) will look like

 // Create and configure the client DefaultODataClient client = new DefaultODataClient(); client.configure(componentsProvider); //Build the query ODataClientQuery query = new BasicODataClientQuery.Builder().withEntityType(Product.class).build(); //Execute the query List<Object> entities = (List<Object>) client.getEntities(requestProperties, query);