HONEYCOMB-270 Add isPresent() to Readers/Customizers

So that they can influence whether empty data is to be considered as present

+ Move registries implementations from util to impl
+ Introduce DelegatingReader trait
+ Extend GenericReader where possible to reduce duplication

Change-Id: I5a416acd0c4eab1fbc30fcbe585719991dbe9215
Signed-off-by: Maros Marsalek <mmarsale@cisco.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/infra/translate-spi/src/main/java/io/fd/honeycomb/translate/spi/read/ReaderCustomizer.java b/infra/translate-spi/src/main/java/io/fd/honeycomb/translate/spi/read/ReaderCustomizer.java
index acfabf5bc..738431eea 100644
--- a/infra/translate-spi/src/main/java/io/fd/honeycomb/translate/spi/read/ReaderCustomizer.java
+++ b/infra/translate-spi/src/main/java/io/fd/honeycomb/translate/spi/read/ReaderCustomizer.java
@@ -57,4 +57,19 @@ public interface ReaderCustomizer<O extends DataObject, B extends Builder<O>> {
     void merge(@Nonnull final Builder<? extends DataObject> parentBuilder, @Nonnull final O readValue);
 
 
+    /**
+     * Check whether the resulting value should be added to the results or ignored.
+     * Invoked after {@link #readCurrentAttributes(InstanceIdentifier, Builder, ReadContext)}
+     *
+     * @param id Keyed instance identifier of read data
+     * @param built Read data as returned from builder
+     *              after {@link #readCurrentAttributes(InstanceIdentifier, Builder, ReadContext)} invocation
+     * @param ctx Read context
+     *
+     * @return true if value is present (even if empty)
+     */
+    default boolean isPresent(final InstanceIdentifier<O> id, final O built, final ReadContext ctx) throws ReadFailedException {
+        // Default impl = check whether read value is empty
+        return !built.equals(getBuilder(id).build());
+    }
 }