Odata ClientEntity错误-预期的OData实体，找到了EntitySet

Question

I'm trying to use Olingo to connect to an Odata v4 service I've tested it with the Northwind sample and the URI that gets produce works in a browser: I always get the following

error:java.lang.IllegalArgumentException:org.apache.olingo.commons.api.serialization.ODataDeserializerException:
com.fasterxml.jackson.core.JsonParseException: Expected OData Entity, found
EntitySet.

Code

ODataEntityRequest<ClientEntity> reqEntity = client.getRetrieveRequestFactory().getEntityRequest(entityURI);
                ODataRetrieveResponse<ClientEntity> entity = reqEntity.execute();
            ClientEntity ce = (ClientEntity)entity.getBody();

at last line i am getting error.

ClientEntity ce = (ClientEntity)entity.getBody();

Answer 1

This error means that you are querying a collection URL like http://services.odata.org/V4/Northwind/Northwind.svc/Categories . The response for this is the EntitySet .

However, seems that you want a single Entity . It can be got from the URL like http://services.odata.org/V4/Northwind/Northwind.svc/Categories(1) , where (1) corresponds with the ID of the Category you want to get.

2 options:

• If you want a single Entity , create a proper URI, eg ODataClientFactory.getClient().newURIBuilder("http://services.odata.org/V4/Northwind/Northwind.svc").appendEntitySetSegment("Categories").appendKeySegment(1).build() and execute a request on this (I think you can even skip the casting thing)
• If you want EntitySet , go for getEntitySetRequest against your uri and then use getBody().getEntities() on the result of the execute() method