This page contains example interceptors that can be registered with the FHIR Storage module.
The following example shows an interceptor that can be used to enhance resources that are submitted for update by a client. In this example, for every time that a Patient resource is created or updated, we are calling a REST MDM service to fetch an EUID (an enterprise identifier for a Patient). We are then adding this EUID as an additional identifier on the list of patient identifiers.
/**
* This example interceptor fetches a set of attributes from a third-party
* REST service and uses them to enhance the resource being submitted.
*/
@SuppressWarnings("unchecked")
public class ExampleAttributeEnhancingInterceptor {
private static final Logger ourLog = LoggerFactory.getLogger(ExampleAttributeEnhancingInterceptor.class);
/**
* We are going to treat creates and updates the same way in this example, so the
* create method redirects to the update method.
*/
@Hook(Pointcut.STORAGE_PRESTORAGE_RESOURCE_CREATED)
public void resourcePreCreate(RequestDetails theRequest, IBaseResource theResource) {
resourcePreUpdate(theRequest, null, theResource);
}
/**
* For this example we are overriding the <code>resourcePreUpdate</code>
* method, which will be called when a resource is being updated. There
* are many other methods that can be overridden, but this one is
* appropriate for the desired functionality.
*
* @param theRequest Contains details about the incoming request. You may wish to cast this
* object to a {@link ca.uhn.fhir.rest.server.servlet.ServletRequestDetails},
* which is always possible when running interceptors inside Smile CDR.
* @param theOldResource The previous version of the resource, before this update was
* requested by the client.
* @param theNewResource The new version of the resource as submitted by the client. This
* object can be modified.
*/
@Hook(Pointcut.STORAGE_PRESTORAGE_RESOURCE_UPDATED)
public void resourcePreUpdate(RequestDetails theRequest, IBaseResource theOldResource, IBaseResource theNewResource) {
// This interceptor only cares about Patient resources
if (!(theNewResource instanceof Patient)) {
return;
}
Patient newResource = (Patient) theNewResource;
/*
* We want to know the primary identifier, which is the first instance of
* Patient.identifier where identifer.system = "http://example.com/mrn". If the
* client has submitted a resourece that does not have such an identifier, this
* is an error and we will throw a PreconditionFailedException (HTTP 412)
*/
String primaryIdentifier = newResource
.getIdentifier()
.stream()
.filter(t -> t.getSystem().equals("http://example.com/mrn"))
.map(t -> t.getValue())
.findFirst()
.orElseThrow(() -> new PreconditionFailedException("No MRN supplied with request"));
// We'll use a system property to pull the port number for this example. If the port
// number won't change across deployments you don't need to do this.
int port = Integer.parseInt(System.getProperty("mqm_query_port"));
// We're going to make a web service call to a simple web service that
// returns a JSON response. There are lots of ways of doing this, but
// in our example we'll make a call using the Spring RestTemplate
RestTemplate restTempate = new RestTemplate();
restTempate.setMessageConverters(Collections.singletonList(new GsonHttpMessageConverter()));
HashMap<String, Object> response = restTempate.getForObject("http://localhost:" + port + "/mdmquery?mrn=" + primaryIdentifier, HashMap.class);
// We'll log the response. Generally this isn't a good idea in a real
// production system but it's handy for debugging at first.
ourLog.info("Response: {}", response);
// Grab the existing EUID (identifier with a system of "http://example.com/euid")
// and create one if it doesn't exist
Identifier euidIdentifier = newResource
.getIdentifier()
.stream()
.filter(t -> t.getSystem().equals("http://example.com/euid"))
.findFirst()
.orElseGet(() -> newResource.addIdentifier());
// Set the identifier value using the web service response
euidIdentifier.setSystem("http://example.com/euid");
euidIdentifier.setValue((String) response.get("euid"));
}
}
The following example shows an interceptor that implements reserved tags. For this example, a reserved tag is a tag that can only be set or removed by the server itself. These tags can not be added or removed by a client, and are hidden from the client as well.
/**
* This interceptor implements the concept of "reserved tags", which are resource tags (tags in
* <code>Resource.meta.tag</code>) that are reserved for internal system use. This means that:
* <ul>
* <li>Clients can not add these tags manually</li>
* <li>Reserved tags are preserved between updates of resources that have them</li>
* <li>The reserved tags are not shown to clients and are filtered before serialization</li>
* </ul>
*
* The assumption with this interceptor is that there is a separate process that manages resource tags.
* This could be a second interceptor, or some other non-client-facing process.
*
* Note that each of the hook methods are annotated with {@literal @Hook(..., order=100)}. The assumption
* here is that a separate interceptor is managing the reserved tags. That interceptor could use
* {@literal @Hook(..., order=101)} to ensure that it comes afterward so that it can add or remove
* the reserved tags as necessary.
*/
@SuppressWarnings("unchecked")
public class TagPreservingInterceptor extends ServerOperationInterceptorAdapter {
private static final Logger ourLog = LoggerFactory.getLogger(TagPreservingInterceptor.class);
private Set<Pair> myTagsToPreserve;
/**
* Constructor
*/
public TagPreservingInterceptor() {
// This is the list of tags we want to preserve
myTagsToPreserve = Collections.unmodifiableSet(Sets.newHashSet(
Pair.of("http://my-tags", "tag1"),
Pair.of("http://my-tags", "tag2")
));
}
/**
* When a new resource is being created, don't allow the client to include any reserved tags
*
* @param theRequest Contains details about the incoming request. You may wish to cast this
* object to a {@link ca.uhn.fhir.rest.server.servlet.ServletRequestDetails},
* which is always possible when running interceptors inside Smile CDR.
* @param theResource The previous resource being created
*/
@Hook(value = Pointcut.STORAGE_PRESTORAGE_RESOURCE_CREATED, order = 100)
public void resourcePreCreate(RequestDetails theRequest, IBaseResource theResource) {
removeReservedTags(theResource);
}
/**
* For this example we are overriding the <code>resourcePreUpdate</code>
* method, which will be called when a resource is being updated. There
* are many other methods that can be overridden, but this one is
* appropriate for the desired functionality.
*
* @param theRequest Contains details about the incoming request. You may wish to cast this
* object to a {@link ca.uhn.fhir.rest.server.servlet.ServletRequestDetails},
* which is always possible when running interceptors inside Smile CDR.
* @param theOldResource The previous version of the resource, before this update was
* requested by the client.
* @param theNewResource The new version of the resource as submitted by the client. This
* object can be modified.
*/
@Hook(value = Pointcut.STORAGE_PRESTORAGE_RESOURCE_UPDATED, order = 100)
public void resourcePreUpdate(RequestDetails theRequest, IBaseResource theOldResource, IBaseResource theNewResource) {
// Filter out any reserved tags
removeReservedTags(theNewResource);
// Copy tags forward
theOldResource
.getMeta()
.getTag()
.stream()
.filter(t -> myTagsToPreserve.contains(Pair.of(t.getSystem(), t.getCode())))
.forEach(t -> theNewResource.getMeta().addTag()
.setSystem(t.getSystem())
.setCode(t.getCode())
.setDisplay(t.getDisplay()));
}
/**
* Before returning any resource to the client, strip the reserved tags
*/
@Hook(value = Pointcut.STORAGE_PRESHOW_RESOURCES)
public void preShow(IPreResourceShowDetails thePreShowDetails) {
for (IBaseResource nextResource : thePreShowDetails) {
removeReservedTags(nextResource);
}
}
private void removeReservedTags(IBaseResource theResource) {
for (Iterator<? extends IBaseCoding> iter = theResource.getMeta().getTag().iterator(); iter.hasNext(); ) {
IBaseCoding nextTag = iter.next();
String system = nextTag.getSystem();
String code = nextTag.getCode();
if (myTagsToPreserve.contains(Pair.of(system, code))) {
iter.remove();
}
}
}
}
function fhirResourcePreCreate(theRequestDetails, theResource) {
if (theResource.name[0].family === "initial-family-name") {
theResource.name[0].family = "after-pre-create";
}
}
function fhirResourceCreated(theRequestDetails, theResource) {
if (theResource.name[0].family === "after-pre-create") {
throw "the resource was created";
}
}
function fhirResourcePreUpdate(theRequestDetails, theOldResource, theNewResource) {
if (theNewResource.resourceType === 'Patient') {
if (theOldResource.name[0].family === 'old-name' && theNewResource.name[0].family === 'new-name') {
theNewResource.name[0].given[0] = 'a-given-name';
}
} else {
Log.info("Unknown resource type " + theNewResource.resourceType);
}
}
function fhirResourceUpdated(theRequestDetails, theOldResource, theNewResource) {
if (theOldResource.name[0].family === 'old-name' && theNewResource.name[0].given[0].toString() === "a-given-name") {
throw "the resource was updated";
}
}
function fhirResourcePreDelete(theRequestDetails, theResource) {
if (theResource.name[0].family === 'removed-family-name') {
theResource.name[0].given[0] = 'b-given-name';
}
}
function fhirResourceDeleted(theRequestDetails, theResource) {
if (theResource.resourceType === 'Patient') {
throw "This patient was deleted";
}
}