[eclipse-ditto#903] improved cloudevents exception handling

* missing specversion lead to 500 error
* exception texts were improved

Signed-off-by: Thomas Jaeckle <thomas.jaeckle@bosch.io>

model/base/src/main/java/org/eclipse/ditto/model/base/exceptions/CloudEventMissingPayloadException.java

@@ -37,8 +37,8 @@ public final class CloudEventMissingPayloadException extends DittoRuntimeExcepti
       */
      public static final String ERROR_CODE = "cloudevent.payload.missing";
 
-     private static final String DEFAULT_MESSAGE = "The cloud event's payload is missing.";
-     private static final String DEFAULT_DESCRIPTION = "Ensure to provide payload in the cloud event.";
+     private static final String DEFAULT_MESSAGE = "The Cloud Event's payload is missing.";
+     private static final String DEFAULT_DESCRIPTION = "Ensure to provide payload in the Cloud Event.";
 
      private static final HttpStatusCode STATUS_CODE = HttpStatusCode.BAD_REQUEST;
 

model/base/src/main/java/org/eclipse/ditto/model/base/exceptions/CloudEventNotParsableException.java

@@ -38,10 +38,10 @@ public final class CloudEventNotParsableException extends DittoRuntimeException
       */
      public static final String ERROR_CODE = "cloudevent.unparsable";
 
-     private static final String DEFAULT_MESSAGE = "The event could not be parsed.";
-     private static final String MESSAGE_PATTERN = "The system was unable to parse the event: {0}";
-     private static final String DESCRIPTION =
-             "Ensure that the event is being transmitted according to the Cloud Events HTTP binding specification v1.0.";
+     private static final String DEFAULT_MESSAGE = "Unable to parse as Cloud Event.";
+     private static final String MESSAGE_PATTERN = "Unable to parse as Cloud Event because of: <{0}>";
+     private static final String DESCRIPTION = "Ensure that the event is being transmitted according to the " +
+             "Cloud Events HTTP binding specification v1.0 and that all mandatory headers were set.";
      private static final URI DEFAULT_URI =
              URI.create("https://github.com/cloudevents/spec/blob/v1.0/http-protocol-binding.md");
 

model/base/src/main/java/org/eclipse/ditto/model/base/exceptions/CloudEventUnsupportedDataSchemaException.java

@@ -38,8 +38,10 @@ public final class CloudEventUnsupportedDataSchemaException extends DittoRuntime
       */
      public static final String ERROR_CODE = "cloudevent.dataschema.unsupported";
 
-     private static final String DEFAULT_MESSAGE = "The data schema is not supported.";
-     private static final String MESSAGE_PATTERN = "The data schema <{0}> is not supported for this resource.";
+     private static final String DEFAULT_MESSAGE = "The provided Cloud Event dataschema is not supported for this " +
+             "resource.";
+     private static final String MESSAGE_PATTERN = "The provided Cloud Event dataschema <{0}> is not supported for " +
+             "this resource.";
      private static final String DESCRIPTION = "Ensure that the URI's scheme is 'ditto', so the complete dataschema " +
              "starts with 'ditto:'";
 

services/gateway/endpoints/src/main/java/org/eclipse/ditto/services/gateway/endpoints/routes/cloudevents/CloudEventsRoute.java

@@ -187,29 +187,28 @@ private CloudEvent toCloudEvent(final RequestContext ctx, final DittoHeaders dit
                     .trace("CloudEvent Ditto Headers: {}", dittoHeaders);
         }
 
-        // create a reader for the message
-        final MessageReader reader = HttpMessageFactory.createReader(acceptor -> {
-
-            // NOTE: this acceptor may be run multiple times by the message reader
-
-            // record if we saw the content type header
-            final AtomicBoolean sawContentType = new AtomicBoolean();
-            // consume the HTTP request headers
-            ctx.getRequest().getHeaders().forEach(header -> {
-                if (header.lowercaseName().equals(DittoHeaderDefinition.CONTENT_TYPE.getKey())) {
-                    sawContentType.set(true);
-                }
-                acceptor.accept(header.name(), header.value());
-            });
-
-            if (!sawContentType.get()) {
-                // we didn't see the content type in the header, so extract it from akka's request
-                acceptor.accept(DittoHeaderDefinition.CONTENT_TYPE.getKey(),
-                        ctx.getRequest().entity().getContentType().mediaType().toString());
-            }
-        }, payload.toArray());
-
         try {
+            // create a reader for the message
+            final MessageReader reader = HttpMessageFactory.createReader(acceptor -> {
+
+                // NOTE: this acceptor may be run multiple times by the message reader
+
+                // record if we saw the content type header
+                final AtomicBoolean sawContentType = new AtomicBoolean();
+                // consume the HTTP request headers
+                ctx.getRequest().getHeaders().forEach(header -> {
+                    if (header.lowercaseName().equals(DittoHeaderDefinition.CONTENT_TYPE.getKey())) {
+                        sawContentType.set(true);
+                    }
+                    acceptor.accept(header.name(), header.value());
+                });
+
+                if (!sawContentType.get()) {
+                    // we didn't see the content type in the header, so extract it from akka's request
+                    acceptor.accept(DittoHeaderDefinition.CONTENT_TYPE.getKey(),
+                            ctx.getRequest().entity().getContentType().mediaType().toString());
+                }
+            }, payload.toArray());
             return reader.toEvent();
         } catch (final CloudEventRWException | IllegalStateException e) {
             throw CloudEventNotParsableException.withDetailedInformationBuilder(e.getMessage())