Add error handling for cds hooks servlet

src/main/java/ca/uhn/fhir/jpa/starter/cdshooks/CdsHooksServlet.java

@@ -44,7 +44,7 @@ public class CdsHooksServlet extends HttpServlet {
 	// CORS Pre-flight
 	@Override
 	protected void doOptions(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
-		//ErrorHandling.setAccessControlHeaders(resp, appProperties);
+		ErrorHandling.setAccessControlHeaders(resp, appProperties);
 		resp.setHeader("Content-Type", ContentType.APPLICATION_JSON.getMimeType());
 		resp.setHeader("X-Content-Type-Options", "nosniff");
 		resp.setStatus(HttpServletResponse.SC_OK);
@@ -59,7 +59,7 @@ public class CdsHooksServlet extends HttpServlet {
 			logger.error(request.getRequestURI());
 			throw new ServletException("This servlet is not configured to handle GET requests.");
 		}
-		//ErrorHandling.setAccessControlHeaders(response, myAppProperties);
+		ErrorHandling.setAccessControlHeaders(response, appProperties);
 		response.setHeader("Content-Type", ContentType.APPLICATION_JSON.getMimeType());
 		response.getWriter().println(new GsonBuilder().setPrettyPrinting().create().toJson(getServices()));
 	}
@@ -90,7 +90,7 @@ public class CdsHooksServlet extends HttpServlet {
 			response.setContentType("text/json;charset=UTF-8");
 			response.getWriter().println(jsonResponse);
 		} catch (BaseServerResponseException e) {
-			// ErrorHandling.handleError(response, "ERROR: Exception connecting to remote server.", e, myAppProperties);
+			ErrorHandling.handleError(response, "ERROR: Exception connecting to remote server.", e, appProperties);
 			logger.error(e.toString());
 		} catch (Exception e) {
 			logger.error(e.toString());

src/main/java/ca/uhn/fhir/jpa/starter/cdshooks/ErrorHandling.java

@@ -0,0 +1,91 @@
+package ca.uhn.fhir.jpa.starter.cdshooks;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.util.Arrays;
+
+import javax.servlet.http.HttpServletResponse;
+
+import ca.uhn.fhir.jpa.starter.AppProperties;
+import ca.uhn.fhir.rest.server.exceptions.BaseServerResponseException;
+
+public class ErrorHandling {
+
+	private ErrorHandling() {}
+
+    public static void handleError(HttpServletResponse response, String message,
+            Exception e, AppProperties myAppProperties)
+            throws IOException {
+        setAccessControlHeaders(response, myAppProperties);
+        response.setStatus(500); // This will be overwritten with the correct status code downstream if needed.
+        response.getWriter().println(message);
+        printMessageAndCause(e, response);
+        if (e instanceof BaseServerResponseException) {
+            handleServerResponseException((BaseServerResponseException) e, response);
+        } else if (e.getCause() instanceof BaseServerResponseException) {
+            handleServerResponseException((BaseServerResponseException) e.getCause(), response);
+        }
+        printStackTrack(e, response);
+    }
+
+    private static void handleServerResponseException(BaseServerResponseException e, HttpServletResponse response)
+            throws IOException {
+        switch (e.getStatusCode()) {
+            case 401:
+            case 403:
+                response.getWriter().println("Precondition Failed. Remote FHIR server returned: " + e.getStatusCode());
+                response.getWriter().println(
+                        "Ensure that the fhirAuthorization token is set or that the remote server allows unauthenticated access.");
+                response.setStatus(412);
+                break;
+            case 404:
+                response.getWriter().println("Precondition Failed. Remote FHIR server returned: " + e.getStatusCode());
+                response.getWriter().println("Ensure the resource exists on the remote server.");
+                response.setStatus(412);
+                break;
+            default:
+                response.getWriter().println("Unhandled Error in Remote FHIR server: " + e.getStatusCode());
+        }
+    }
+
+    private static void printMessageAndCause(Exception e, HttpServletResponse response) throws IOException {
+        if (e.getMessage() != null) {
+            response.getWriter().println(e.getMessage());
+        }
+
+        if (e.getCause() != null && e.getCause().getMessage() != null) {
+            response.getWriter().println(e.getCause().getMessage());
+        }
+    }
+
+    private static void printStackTrack(Exception e, HttpServletResponse response) throws IOException {
+        StringWriter sw = new StringWriter();
+        e.printStackTrace(new PrintWriter(sw));
+        String exceptionAsString = sw.toString();
+        response.getWriter().println(exceptionAsString);
+    }
+
+    public static void setAccessControlHeaders(HttpServletResponse resp, AppProperties myAppProperties) {
+        if (myAppProperties.getCors() != null) {
+            if (myAppProperties.getCors().getAllow_Credentials()) {
+                resp.setHeader("Access-Control-Allow-Origin",
+                        myAppProperties.getCors().getAllowed_origin().stream().findFirst().get());
+                resp.setHeader("Access-Control-Allow-Methods",
+                        String.join(", ", Arrays.asList("GET", "HEAD", "POST", "OPTIONS")));
+                resp.setHeader("Access-Control-Allow-Headers",
+                        String.join(", ", Arrays.asList("x-fhir-starter", "Origin",
+                                "Accept", "X-Requested-With", "Content-Type", "Authorization", "Cache-Control")));
+                resp.setHeader("Access-Control-Expose-Headers",
+                        String.join(", ", Arrays.asList("Location", "Content-Location")));
+                resp.setHeader("Access-Control-Max-Age", "86400");
+            }
+        }
+    }
+
+    public static class CdsHooksError extends RuntimeException {
+        public CdsHooksError(String message) {
+            super(message);
+        }
+    }
+}

src/main/java/ca/uhn/fhir/jpa/starter/cdshooks/StarterCdsHooksConfig.java

@@ -1,16 +1,12 @@
 package ca.uhn.fhir.jpa.starter.cdshooks;
 
 import org.hl7.fhir.instance.model.api.IBaseResource;
-import org.springframework.beans.factory.FactoryBean;
-import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
 import org.springframework.boot.web.servlet.ServletRegistrationBean;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 
-import ca.uhn.fhir.jpa.cache.IResourceChangeListenerRegistry;
-import ca.uhn.fhir.rest.server.RestfulServer;
 import ca.uhn.hapi.fhir.cdshooks.api.ICdsHooksDaoAuthorizationSvc;
 import ca.uhn.hapi.fhir.cdshooks.config.CdsHooksConfig;
 import ca.uhn.hapi.fhir.cdshooks.svc.CdsHooksContextBooter;