I implemented an OData V2 Service with Apache Olingo V2 in connectin with JPA using EclipseLink. All requests are working fine, but when it comes to the point, where I want to access a single property via GET request from an entity set like for the following URL:
http://localhost:8080/MyODataService/XXXXXX.svc/EntitySet(12345)/Property
the response in return is:
<error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">
<code/>
<message xml:lang="de-DE">Not implemented</message>
</error>
The class which extends the ODataJPASeviceFactory looks as follows:
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import org.apache.olingo.odata2.jpa.processor.api.ODataJPAContext;
import org.apache.olingo.odata2.jpa.processor.api.ODataJPAServiceFactory;
import org.apache.olingo.odata2.jpa.processor.api.exception.ODataJPARuntimeException;
public class JPAODataServiceFactory extends ODataJPAServiceFactory
{
private static final String PERSISTENCE_UNIT_NAME = "MyPersistenceUnitName";
@Override
public ODataJPAContext initializeODataJPAContext() throws ODataJPARuntimeException
{
ODataJPAContext oDatJPAContext = this.getODataJPAContext();
try
{
EntityManagerFactory emf = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
oDatJPAContext.setEntityManagerFactory(emf);
oDatJPAContext.setPersistenceUnitName(PERSISTENCE_UNIT_NAME);
return oDatJPAContext;
} catch (Exception e)
{
throw new RuntimeException(e);
}
}
My question now is: How do I implement the functionality, so that I can do GET and POST requests not only for a whole entity set, but also for a single property of an entity set like I tried with the mentioned URL?
Accessing a single property from one entity is currently not implemented if you use the Olingo JPA Extension.
If you want to support this behaviour you can register a custom processor and only override the "readEntityComplexProperty" and "readEntitySimpleProperty" methods. There you can have your custom code where you specifically get back the value. Every method you don`t override will result in the standard Olingo functionality being executed.
Here is a tutorial on how to register a custom JPA processor: http://olingo.apache.org/doc/odata2/tutorials/CustomODataJPAProcessor.html
Here is the example on how your code can look like if you implement the functionality yourself: https://github.com/apache/olingo-odata2/blob/597465569fdd15976d0486711d4a38f93a7c6696/odata2-lib/odata-ref/src/main/java/org/apache/olingo/odata2/ref/processor/ListsProcessor.java#L592
You need to create an association between your entity sets. For example, to access the following URL: http://localhost:8080/myService.svc/Cars ('6')/Manufacturer, you need to create an assocation between your car and your manufacturer association sets. Have a look at the documentation: https://olingo.apache.org/doc/odata2/tutorials/basicread.html
Hegg,
you can use
http://localhost:8080/MyODataService/XXXXXX.svc/EntitySet(12345)/ ?$select=Property
Bye
Domenico
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