Change App2mzs Interface and Init Delivery Pipeline

- Change app2mzs interface: output message from
  app2mzs:DeliveryRequest was app2mzs:DeliveryResponse, now its
  msg:DeliveryRequestStatus. Reason: ZD returns
  msg:DeliveryRequestStatus which is signed. Moazs does not convert
  msg:DeliveryRequestStatus into app2mzs:DeliveryResponse because the
  conversion woudl break the signature.
- App2MzsService: Make beans final and inject them with constructor;
  Refactor DeliveryRequestHandler into App2MZSService.
- DeliveryPipeline: Add Interface and a "SameThreadImplementation"
  that executes the pipeline in the same threat and can be used in
  single mode.
- DeliveryRepository: Augment interface for storing and retrieving
  request status objects; Add in-memory-implementation for status objects.
- Utils: Add helper function for coalescing multiple values

1 files changed, 33 insertions, 0 deletions

diff --git a/src/main/java/at/gv/egiz/moazs/util/NullCoalesce.java b/src/main/java/at/gv/egiz/moazs/util/NullCoalesce.java
new file mode 100644
index 0000000..4377140
--- /dev/null
+++ b/src/main/java/at/gv/egiz/moazs/util/NullCoalesce.java
@@ -0,0 +1,33 @@
+package at.gv.egiz.moazs.util;
+
+import java.util.Optional;
+
+import static java.util.Optional.ofNullable;
+
+/**
+ * Helper function for coalescing nullables value without cluttering code with if-else cascades
+ * @author les2
+ * @source https://stackoverflow.com/questions/2768054/how-to-get-the-first-non-null-value-in-java
+ */
+public class NullCoalesce {
+
+    /**
+     * @return the first not-null value
+     * @param a
+     * @param b
+     * @param <T>
+     * @return a if a != null, otherwise b.
+     */
+    public static <T> Optional<T> coalesce(T a, T b) {
+        return a != null ? ofNullable(a) : ofNullable(b);
+    }
+
+    public static <T> Optional<T> coalesce(T a, T b, T c) {
+        return a != null ? ofNullable(a) : coalesce(b,c);
+    }
+
+    public static <T> Optional<T> coalesce(T a, T b, T c, T d) {
+        return a != null ? ofNullable(a) : coalesce(b,c,d);
+    }
+
+}