Allow custom operations/providers in addition to interceptors (#654)

* Allow custom operations/providers to be added in the same way custom interceptors are currently loaded

* Add new property to documentation and default yaml file

* Add test for custom operation

src/main/java/ca/uhn/fhir/jpa/starter/AppProperties.java

@@ -97,12 +97,16 @@ public class AppProperties {
 
   private final List<String> custom_interceptor_classes = new ArrayList<>();
 
+	private final List<String> custom_provider_classes = new ArrayList<>();
 
 
 	public List<String> getCustomInterceptorClasses() {
     return custom_interceptor_classes;
   }
 
+	public List<String> getCustomProviderClasses() {
+		return custom_provider_classes;
+	}
 
 
 	public Boolean getOpenapi_enabled() {

src/main/java/ca/uhn/fhir/jpa/starter/common/StarterJpaConfig.java

@@ -455,6 +455,9 @@ public class StarterJpaConfig {
 			fhirServer.registerProvider(theIpsOperationProvider.get());
 		}
 
+		// register custom providers
+		registerCustomProviders(fhirServer, appContext, appProperties.getCustomProviderClasses());
+
 		return fhirServer;
 	}
 
@@ -497,6 +500,45 @@ public class StarterJpaConfig {
 		}
 	}
 
+	/**
+	 * check the properties for custom provider classes and registers them.
+	 */
+	@SuppressWarnings({"unchecked", "rawtypes"})
+	private void registerCustomProviders(
+		RestfulServer fhirServer, ApplicationContext theAppContext, List<String> customProviderClasses) {
+
+		if (customProviderClasses == null) {
+			return;
+		}
+
+		for (String className : customProviderClasses) {
+			Class clazz;
+			try {
+				clazz = Class.forName(className);
+			} catch (ClassNotFoundException e) {
+				throw new ConfigurationException("Provider class was not found on classpath: " + className, e);
+			}
+
+			// first check if the class a Bean in the app context
+			Object provider = null;
+			try {
+				provider = theAppContext.getBean(clazz);
+			} catch (NoSuchBeanDefinitionException ex) {
+				// no op - if it's not a bean we'll try to create it
+			}
+
+			// if not a bean, instantiate the interceptor via reflection
+			if (provider == null) {
+				try {
+					provider = clazz.getConstructor().newInstance();
+				} catch (Exception e) {
+					throw new ConfigurationException("Unable to instantiate provider class : " + className, e);
+				}
+			}
+			fhirServer.registerProvider(provider);
+		}
+	}
+
 	public static IServerConformanceProvider<?> calculateConformanceProvider(
 			IFhirSystemDao fhirSystemDao,
 			RestfulServer fhirServer,

src/main/resources/application.yaml

@@ -178,6 +178,11 @@ hapi:
     # or will be instantiated via reflection using an no-arg contructor; then registered with the server  
     #custom-interceptor-classes:  
 
+    # comma-separated list of fully qualified provider classes. 
+    # classes listed here will be fetched from the Spring context when combined with 'custom-bean-packages', 
+    # or will be instantiated via reflection using an no-arg contructor; then registered with the server  
+    #custom-provider-classes:  
+    
     # Threadpool size for BATCH'ed GETs in a bundle.
     #    bundle_batch_pool_size: 10
     #    bundle_batch_pool_max_size: 50