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FHIR Connectathon 7 for Java Dummies

David Hay

Last week we had a look at using the .net client to access a FHIR server as a lead up to the next connectathon. I thought it might be fun to do the same thing using the HAPI Java client (Now that it’s at release .5 – half way there!).

Now a disclaimer: I am not a Java developer – in fact I’m learning Java doing this work. In some ways I’d rather be in the .net world, but I’m a Mac user, and .net plays uneasily on that platform, so Java it is. (Yes, I know there’s Mono – it just doesn’t work for me for some reason).

I am using an IDE (be crazy otherwise) – I went for the IntelliJ IDEA IDE as I use their webstorm product for JavaScript development and like it. There’s a free version which is enough for the contents of this post, though I’ve used the full version as I use the Tomcat integration (more on that later).

So here are the steps I followed.

  1. Download the HAPI libraries and unzip to a suitable location. You can also use Maven which is what the real developers would use – a bit too much for me at the moment…
  2. Create a new console application. (Create a new project but don’t select any templates on the front page – the next page is where you can select a console app. Not the most intuitive I must admit).
  3. Create a reference to the HAPI Library, which is in the file you downloaded above. (To get there go: File > Project Structure > Libraries, click the ‘+’, select a java library and then select the folder)
  4. You also need to add a reference to the ‘dependencies’ sub-folder using the same process.
  5. Now you can add the code you need. This is what I ended up with:
import ca.uhn.fhir.context.FhirContext;
import ca.uhn.fhir.model.api.Bundle;
import ca.uhn.fhir.model.dstu.resource.Conformance;
import ca.uhn.fhir.model.dstu.resource.Patient;
import ca.uhn.fhir.model.dstu.valueset.AdministrativeGenderCodesEnum;
import ca.uhn.fhir.rest.client.IGenericClient;
import ca.uhn.fhir.rest.server.exceptions.ResourceNotFoundException;

//Code copied very substantially from http://jamesagnew.github.io/hapi-fhir/doc_rest_client.html

public class Main {

    public static void main(String[] args) {

        //create the FHIR context
        FhirContext ctx = new FhirContext();
        String serverBase = "https://fhir.orionhealth.com/blaze/fhir";
        IGenericClient client = ctx.newRestfulGenericClient(serverBase);

        // Retrieve the server's conformance statement and print its description
        Conformance conf = client.conformance();
        System.out.println(conf.getDescription().getValue());


        //Read a single patient
        //String id = "1";        //this is not found on the server, and will throw an exception
        String id = "77662";
        try {
            Patient patient = client.read(Patient.class, id);
            //Do something with patient

            // Change the patient gender
            patient.setGender(AdministrativeGenderCodesEnum.M);
            //and save...
            client.update(id, patient);

        } catch (ResourceNotFoundException ex) {
            System.out.println("No patient with the ID of " + id);
        } catch (Exception ex){
            System.out.println("Unexpected error: " + ex.getMessage());
        }

        //Create a new Patient
        Patient newPatient = new Patient();
        newPatient.addIdentifier("urn:oid:2.16.840.1.113883.2.18.2", "PRP1660");
        newPatient.addName().addFamily("Power").addGiven("Cold");
        client.create()
                .resource(newPatient)
                .encodedJson()
                .execute();

        //do a simple search
        Bundle bundle = client.search()
                .forResource(Patient.class)
                .where(Patient.NAME.matches().value("eve"))
                .execute();
        //bundle will be a HAPI bundle of patients
        System.out.println(bundle.getTitle());
        System.out.println(bundle.getEntries().size() + " matches.");

    }
}

 

One nice thing about the IDE is that it will add the ‘import’ statements for you (if you’ve set up the references in steps 3 & 4 above). Just type in the name of the class (which will auto-complete). It goes red to indicate it can’t find it, then displays a popup offering to import it. Pressing <Alt><Enter> adds the import. Cool!

So looking at the code (and comparing it with the .net version) you’ll see more similarities than differences in approach (this is by design – I love open source!), although there are differences due to the different platforms. Much of this code has been copied from the HAPI site with only minor changes to defend against charges of plagiarism…

So there you have it: Track 1 of the Connectathon done for you! No excuses! (Actually I didn’t do the history scenario – but that should easy for you now – and there’s even an example in the HAPI docs).

One thing I did note is that HAPI is quite verbose in its logging – this can be controlled using ‘LoggingInterceptors‘ – I’ll have to have a play with them next.

If I’m being honest (generally a good policy) I have to admit to an ulterior purpose in doing this myself rather than getting someone else to do it for me (as Peter kindly did for the .net version). I want to use HAPI to build a ‘proxy’ between our existing services and a FHIR interface, and as we’re a Java shop HAPI in a servlet container made the most sense. HAPI offers the basic infrastructure to build a FHIR server, which will save a lot of effort. I’ve pretty much got that working – and I’ll report on that in another post.

See you at Connectathon!

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