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>

42 files changed, 282 insertions, 236 deletions

diff --git a/infra/it/benchmark/src/main/java/io/fd/honeycomb/benchmark/util/StaticReader.java b/infra/it/benchmark/src/main/java/io/fd/honeycomb/benchmark/util/StaticReader.java
index 90e560152..76ad0e3d4 100644
--- a/infra/it/benchmark/src/main/java/io/fd/honeycomb/benchmark/util/StaticReader.java
+++ b/infra/it/benchmark/src/main/java/io/fd/honeycomb/benchmark/util/StaticReader.java
@@ -55,6 +55,11 @@ public final class StaticReader<T extends DataObject, B extends Builder<T>> impl
                 '}';
     }
 
+    @Override
+    public boolean isPresent(final InstanceIdentifier<T> id, final T built, final ReadContext ctx) {
+        return true;
+    }
+
     @Nonnull
     @Override
     public Optional<? extends DataObject> read(@Nonnull final InstanceIdentifier<? extends DataObject> id,
diff --git a/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombReadInfraTest.java b/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombReadInfraTest.java
index 5ec2b55ba..6d4c9e6f3 100644
--- a/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombReadInfraTest.java
+++ b/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombReadInfraTest.java
@@ -24,6 +24,7 @@ import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.anyListOf;
 import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.atLeastOnce;
+import static org.mockito.Mockito.atMost;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.inOrder;
@@ -36,6 +37,8 @@ import com.google.common.collect.Lists;
 import com.google.common.collect.Multimap;
 import com.google.common.util.concurrent.CheckedFuture;
 import io.fd.honeycomb.translate.impl.read.GenericListReader;
+import io.fd.honeycomb.translate.impl.read.GenericReader;
+import io.fd.honeycomb.translate.impl.read.registry.CompositeReaderRegistryBuilder;
 import io.fd.honeycomb.translate.read.ListReader;
 import io.fd.honeycomb.translate.read.ReadContext;
 import io.fd.honeycomb.translate.read.ReadFailedException;
@@ -43,8 +46,7 @@ import io.fd.honeycomb.translate.read.Reader;
 import io.fd.honeycomb.translate.read.registry.ReaderRegistry;
 import io.fd.honeycomb.translate.util.RWUtils;
 import io.fd.honeycomb.translate.util.read.ReflexiveListReaderCustomizer;
-import io.fd.honeycomb.translate.util.read.ReflexiveReader;
-import io.fd.honeycomb.translate.util.read.registry.CompositeReaderRegistryBuilder;
+import io.fd.honeycomb.translate.util.read.ReflexiveReaderCustomizer;
 import java.lang.reflect.InvocationTargetException;
 import java.util.List;
 import java.util.stream.Collectors;
@@ -185,8 +187,11 @@ public class HoneycombReadInfraTest extends AbstractInfraTest {
         }
     }
 
-    private <D extends DataObject, B extends Builder<D>> void verifyNoMoreReadInteractions(final Reader<D, B> reader) {
+    private <D extends DataObject, B extends Builder<D>> void verifyNoMoreReadInteractions(final Reader<D, B> reader)
+            throws ReadFailedException {
         verify(reader, atLeastOnce()).getManagedDataObjectType();
+        // Just mark all the isPresent calls as verified
+        verify(reader, atMost(100)).isPresent(any(InstanceIdentifier.class), any(), any());
         verifyNoMoreInteractions(reader);
     }
 
@@ -254,7 +259,8 @@ public class HoneycombReadInfraTest extends AbstractInfraTest {
     static <D extends DataObject, B extends Builder<D>> Reader<D, B> mockReader(InstanceIdentifier<D> id,
                                                                                  CurrentAttributesReader<D, B> currentAttributesReader,
                                                                                  Class<B> builderClass) {
-        final ReflexiveReader<D, B> reflex = new ReflexiveReader<D, B>(id, builderClass) {
+        final Reader<D, B> reflex = new GenericReader<D, B>(id,
+                new ReflexiveReaderCustomizer<>(id.getTargetType(), builderClass)) {
 
             @Override
             public void readCurrentAttributes(@Nonnull final InstanceIdentifier<D> id,
@@ -270,6 +276,7 @@ public class HoneycombReadInfraTest extends AbstractInfraTest {
         final Reader<D, B> mock = mock(Reader.class);
         try {
             doAnswer(i -> reflexiveAnswer(reflex, i)).when(mock).read(any(InstanceIdentifier.class), any(ReadContext.class));
+            doAnswer(i -> reflexiveAnswer(reflex, i)).when(mock).isPresent(any(InstanceIdentifier.class), any(), any());
             doAnswer(i -> reflexiveAnswer(reflex, i)).when(mock)
                     .readCurrentAttributes(any(InstanceIdentifier.class), any(builderClass), any(ReadContext.class));
             doAnswer(i -> reflexiveAnswer(reflex, i)).when(mock).merge(any(Builder.class), any(id.getTargetType()));
@@ -311,6 +318,7 @@ public class HoneycombReadInfraTest extends AbstractInfraTest {
             // not using eq(id) instead using any(InstanceIdentifier.class) due to InstanceIdentifier.equals weird behavior
             // with wildcarded instance identifiers for lists
             doAnswer(i -> reflexiveAnswer(reflex, i)).when(mock).read(any(InstanceIdentifier.class), any(ReadContext.class));
+            doAnswer(i -> reflexiveAnswer(reflex, i)).when(mock).isPresent(any(InstanceIdentifier.class), any(), any());
             doAnswer(i -> reflexiveAnswer(reflex, i)).when(mock)
                     .readCurrentAttributes(any(InstanceIdentifier.class), any(builderClass), any(ReadContext.class));
             doAnswer(i -> reflexiveAnswer(reflex, i)).when(mock).merge(any(Builder.class), any(id.getTargetType()));
diff --git a/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombSubtreeReadInfraTest.java b/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombSubtreeReadInfraTest.java
index 5bb81b477..1894f4942 100644
--- a/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombSubtreeReadInfraTest.java
+++ b/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombSubtreeReadInfraTest.java
@@ -32,7 +32,7 @@ import io.fd.honeycomb.translate.read.ReadFailedException;
 import io.fd.honeycomb.translate.read.Reader;
 import io.fd.honeycomb.translate.read.registry.ReaderRegistry;
 import io.fd.honeycomb.translate.util.read.ReflexiveListReaderCustomizer;
-import io.fd.honeycomb.translate.util.read.registry.CompositeReaderRegistryBuilder;
+import io.fd.honeycomb.translate.impl.read.registry.CompositeReaderRegistryBuilder;
 import java.util.List;
 import java.util.stream.Collectors;
 import javax.annotation.Nonnull;
diff --git a/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombWriteInfraTest.java b/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombWriteInfraTest.java
index 12ae6568d..bd51e39de 100644
--- a/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombWriteInfraTest.java
+++ b/infra/it/it-test/src/test/java/io/fd/honeycomb/data/impl/HoneycombWriteInfraTest.java
@@ -29,7 +29,7 @@ import static org.mockito.Mockito.when;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Sets;
 import io.fd.honeycomb.data.DataModification;
-import io.fd.honeycomb.translate.util.write.registry.FlatWriterRegistryBuilder;
+import io.fd.honeycomb.translate.impl.write.registry.FlatWriterRegistryBuilder;
 import io.fd.honeycomb.translate.write.WriteFailedException;
 import io.fd.honeycomb.translate.write.WriteContext;
 import io.fd.honeycomb.translate.write.Writer;
diff --git a/infra/minimal-distribution/src/main/java/io/fd/honeycomb/infra/distro/data/config/WriterRegistryProvider.java b/infra/minimal-distribution/src/main/java/io/fd/honeycomb/infra/distro/data/config/WriterRegistryProvider.java
index f3e8ce200..fa0c298fb 100644
--- a/infra/minimal-distribution/src/main/java/io/fd/honeycomb/infra/distro/data/config/WriterRegistryProvider.java
+++ b/infra/minimal-distribution/src/main/java/io/fd/honeycomb/infra/distro/data/config/WriterRegistryProvider.java
@@ -18,7 +18,7 @@ package io.fd.honeycomb.infra.distro.data.config;
 
 import com.google.inject.Inject;
 import io.fd.honeycomb.infra.distro.ProviderTrait;
-import io.fd.honeycomb.translate.util.write.registry.FlatWriterRegistryBuilder;
+import io.fd.honeycomb.translate.impl.write.registry.FlatWriterRegistryBuilder;
 import io.fd.honeycomb.translate.write.WriterFactory;
 import io.fd.honeycomb.translate.write.registry.ModifiableWriterRegistryBuilder;
 import java.util.HashSet;
diff --git a/infra/minimal-distribution/src/main/java/io/fd/honeycomb/infra/distro/data/oper/ReaderRegistryBuilderProvider.java b/infra/minimal-distribution/src/main/java/io/fd/honeycomb/infra/distro/data/oper/ReaderRegistryBuilderProvider.java
index 05177d54d..ab967e164 100644
--- a/infra/minimal-distribution/src/main/java/io/fd/honeycomb/infra/distro/data/oper/ReaderRegistryBuilderProvider.java
+++ b/infra/minimal-distribution/src/main/java/io/fd/honeycomb/infra/distro/data/oper/ReaderRegistryBuilderProvider.java
@@ -20,7 +20,7 @@ import com.google.inject.Inject;
 import io.fd.honeycomb.infra.distro.ProviderTrait;
 import io.fd.honeycomb.translate.read.ReaderFactory;
 import io.fd.honeycomb.translate.read.registry.ModifiableReaderRegistryBuilder;
-import io.fd.honeycomb.translate.util.read.registry.CompositeReaderRegistryBuilder;
+import io.fd.honeycomb.translate.impl.read.registry.CompositeReaderRegistryBuilder;
 import java.util.HashSet;
 import java.util.Set;
 
diff --git a/infra/translate-api/src/main/java/io/fd/honeycomb/translate/read/Reader.java b/infra/translate-api/src/main/java/io/fd/honeycomb/translate/read/Reader.java
index dd9944624..7138006e0 100644
--- a/infra/translate-api/src/main/java/io/fd/honeycomb/translate/read/Reader.java
+++ b/infra/translate-api/src/main/java/io/fd/honeycomb/translate/read/Reader.java
@@ -35,6 +35,21 @@ public interface Reader<D extends DataObject, B extends Builder<D>> extends Subt
     // TODO HONEYCOMB-169 make async
 
     /**
+     * Check whether the data from current reader are present or not.
+     * 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 the result value is present.
+     */
+    boolean isPresent(@Nonnull InstanceIdentifier<D> id, @Nonnull D built, @Nonnull ReadContext ctx)
+            throws ReadFailedException;
+
+    /**
      * Reads data identified by id
      *
      * @param id unique identifier of subtree to be read. The subtree must contain managed data object type. For
diff --git a/infra/translate-impl/pom.xml b/infra/translate-impl/pom.xml
index 7892e90af..b431c07f9 100644
--- a/infra/translate-impl/pom.xml
+++ b/infra/translate-impl/pom.xml
@@ -46,6 +46,13 @@
             <artifactId>translate-utils</artifactId>
             <version>${project.version}</version>
         </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>translate-utils</artifactId>
+            <version>${project.version}</version>
+            <type>test-jar</type>
+            <scope>test</scope>
+        </dependency>
 
         <dependency>
             <groupId>junit</groupId>
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericListReader.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericListReader.java
index ad93e8fe9..b06ac060f 100644
--- a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericListReader.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericListReader.java
@@ -25,7 +25,6 @@ import io.fd.honeycomb.translate.read.ReadContext;
 import io.fd.honeycomb.translate.read.ReadFailedException;
 import io.fd.honeycomb.translate.spi.read.ListReaderCustomizer;
 import io.fd.honeycomb.translate.util.RWUtils;
-import io.fd.honeycomb.translate.util.read.AbstractGenericReader;
 import java.util.ArrayList;
 import java.util.List;
 import javax.annotation.Nonnull;
@@ -48,12 +47,10 @@ import org.slf4j.LoggerFactory;
 @Beta
 @ThreadSafe
 public class GenericListReader<C extends DataObject & Identifiable<K>, K extends Identifier<C>, B extends Builder<C>>
-        extends AbstractGenericReader<C, B> implements ListReader<C, K, B> {
+        extends GenericReader<C, B> implements ListReader<C, K, B> {
 
     private static final Logger LOG = LoggerFactory.getLogger(GenericListReader.class);
 
-    protected final ListReaderCustomizer<C, K, B> customizer;
-
     /**
      * Create new {@link GenericListReader}
      *
@@ -62,8 +59,7 @@ public class GenericListReader<C extends DataObject & Identifiable<K>, K extends
      */
     public GenericListReader(@Nonnull final InstanceIdentifier<C> managedDataObjectType,
                              @Nonnull final ListReaderCustomizer<C, K, B> customizer) {
-        super(managedDataObjectType);
-        this.customizer = customizer;
+        super(managedDataObjectType, customizer);
     }
 
     @Override
@@ -92,31 +88,13 @@ public class GenericListReader<C extends DataObject & Identifiable<K>, K extends
     public List<K> getAllIds(@Nonnull final InstanceIdentifier<C> id, @Nonnull final ReadContext ctx)
             throws ReadFailedException {
         LOG.trace("{}: Getting all list ids", this);
-        final List<K> allIds = customizer.getAllIds(id, ctx);
+        final List<K> allIds = ((ListReaderCustomizer<C, K, B>) customizer).getAllIds(id, ctx);
         LOG.debug("{}: All list ids: {}", this, allIds);
         return allIds;
     }
 
     @Override
     public void merge(@Nonnull final Builder<? extends DataObject> builder, @Nonnull final List<C> readData) {
-        customizer.merge(builder, readData);
-    }
-
-    @Override
-    public void readCurrentAttributes(@Nonnull final InstanceIdentifier<C> id, @Nonnull final B builder,
-                                      @Nonnull final ReadContext ctx)
-            throws ReadFailedException {
-        try {
-            customizer.readCurrentAttributes(id, builder, ctx);
-        } catch (RuntimeException e) {
-            throw new ReadFailedException(id, e);
-        }
+        ((ListReaderCustomizer<C, K, B>) customizer).merge(builder, readData);
     }
-
-    @Nonnull
-    @Override
-    public B getBuilder(@Nonnull final InstanceIdentifier<C> id) {
-        return customizer.getBuilder(id);
-    }
-
 }
diff --git a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericReader.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericReader.java
index e76b6e9a3..2bf439f82 100644
--- a/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericReader.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/GenericReader.java
@@ -22,6 +22,7 @@ import io.fd.honeycomb.translate.read.ReadFailedException;
 import io.fd.honeycomb.translate.read.Reader;
 import io.fd.honeycomb.translate.spi.read.ReaderCustomizer;
 import io.fd.honeycomb.translate.util.read.AbstractGenericReader;
+import io.fd.honeycomb.translate.util.read.ReflexiveReaderCustomizer;
 import javax.annotation.Nonnull;
 import javax.annotation.concurrent.ThreadSafe;
 import org.opendaylight.yangtools.concepts.Builder;
@@ -73,4 +74,14 @@ public class GenericReader<C extends DataObject, B extends Builder<C>>
         customizer.merge(parentBuilder, readValue);
     }
 
+    @Override
+    public boolean isPresent(final InstanceIdentifier<C> id, final C built, final ReadContext ctx)
+            throws ReadFailedException {
+        return customizer.isPresent(id, built, ctx);
+    }
+
+    public static <C extends DataObject, B extends Builder<C>> Reader<C, B> createReflexive(
+            final InstanceIdentifier<C> id, Class<B> builderClass) {
+        return new GenericReader<>(id, new ReflexiveReaderCustomizer<>(id.getTargetType(), builderClass));
+    }
 }
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/CompositeReader.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReader.java
index b52fd09ec..ec82b3f7f 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/CompositeReader.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReader.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import static com.google.common.base.Preconditions.checkArgument;
 
@@ -31,6 +31,7 @@ import io.fd.honeycomb.translate.read.ReadFailedException;
 import io.fd.honeycomb.translate.read.Reader;
 import io.fd.honeycomb.translate.util.RWUtils;
 import io.fd.honeycomb.translate.util.read.AbstractGenericReader;
+import io.fd.honeycomb.translate.util.read.DelegatingReader;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -46,7 +47,7 @@ import org.slf4j.LoggerFactory;
 
 class CompositeReader<D extends DataObject, B extends Builder<D>>
         extends AbstractGenericReader<D, B>
-        implements Initializer<D> {
+        implements Initializer<D>, DelegatingReader<D, B> {
 
     private static final Logger LOG = LoggerFactory.getLogger(CompositeReader.class);
 
@@ -131,6 +132,11 @@ class CompositeReader<D extends DataObject, B extends Builder<D>>
     }
 
     @Override
+    public Reader<D, B> getDelegate() {
+        return delegate;
+    }
+
+    @Override
     public void readCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final B builder,
                                       @Nonnull final ReadContext ctx)
             throws ReadFailedException {
@@ -138,17 +144,6 @@ class CompositeReader<D extends DataObject, B extends Builder<D>>
         readChildren(id, ctx, builder);
     }
 
-    @Nonnull
-    @Override
-    public B getBuilder(final InstanceIdentifier<D> id) {
-        return delegate.getBuilder(id);
-    }
-
-    @Override
-    public void merge(@Nonnull final Builder<? extends DataObject> parentBuilder, @Nonnull final D readValue) {
-        delegate.merge(parentBuilder, readValue);
-    }
-
     /**
      * Wrap a Reader as a Composite Reader.
      */
@@ -181,7 +176,7 @@ class CompositeReader<D extends DataObject, B extends Builder<D>>
 
     private static class CompositeListReader<D extends DataObject & Identifiable<K>, B extends Builder<D>, K extends Identifier<D>>
             extends CompositeReader<D, B>
-            implements InitListReader<D, K, B> {
+            implements DelegatingListReader<D, K, B>, InitListReader<D, K, B> {
 
         private final ListReader<D, K, B> delegate;
 
@@ -191,6 +186,10 @@ class CompositeReader<D extends DataObject, B extends Builder<D>>
             this.delegate = reader;
         }
 
+        public ListReader<D, K, B> getDelegate() {
+            return delegate;
+        }
+
         @Nonnull
         @Override
         public List<D> readList(@Nonnull final InstanceIdentifier<D> id, @Nonnull final ReadContext ctx)
@@ -226,16 +225,5 @@ class CompositeReader<D extends DataObject, B extends Builder<D>>
                 throw new InitFailedException(id, e);
             }
         }
-
-        @Override
-        public void merge(@Nonnull final Builder<? extends DataObject> builder, @Nonnull final List<D> readData) {
-            delegate.merge(builder, readData);
-        }
-
-        @Override
-        public List<K> getAllIds(@Nonnull final InstanceIdentifier<D> id,
-                                 @Nonnull final ReadContext ctx) throws ReadFailedException {
-            return delegate.getAllIds(id, ctx);
-        }
     }
 }
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/CompositeReaderRegistry.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistry.java
index 9505a7730..d69e53765 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/CompositeReaderRegistry.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistry.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/CompositeReaderRegistryBuilder.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistryBuilder.java
index da9bbe934..290c5d4aa 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/CompositeReaderRegistryBuilder.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistryBuilder.java
@@ -14,16 +14,16 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import com.google.common.collect.ImmutableMap;
+import io.fd.honeycomb.translate.impl.read.GenericReader;
 import io.fd.honeycomb.translate.read.InitReader;
 import io.fd.honeycomb.translate.read.Reader;
 import io.fd.honeycomb.translate.read.registry.ModifiableReaderRegistryBuilder;
 import io.fd.honeycomb.translate.read.registry.ReaderRegistry;
 import io.fd.honeycomb.translate.read.registry.ReaderRegistryBuilder;
 import io.fd.honeycomb.translate.util.AbstractSubtreeManagerRegistryBuilderBuilder;
-import io.fd.honeycomb.translate.util.read.ReflexiveReader;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
@@ -54,11 +54,9 @@ public final class CompositeReaderRegistryBuilder
     @Override
     public <D extends DataObject> void addStructuralReader(@Nonnull InstanceIdentifier<D> id,
                                                            @Nonnull Class<? extends Builder<D>> builderType) {
-        add(new ReflexiveReader<>(id, builderType));
+        add(GenericReader.createReflexive(id, builderType));
     }
 
-
-
     /**
      * Create {@link CompositeReaderRegistry} with Readers ordered according to submitted relationships.
      * <p/>
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/InitSubtreeReader.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/InitSubtreeReader.java
index 4edc38f9d..809cdb214 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/InitSubtreeReader.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/InitSubtreeReader.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import io.fd.honeycomb.translate.read.InitFailedException;
 import io.fd.honeycomb.translate.read.InitListReader;
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/SubtreeReader.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/SubtreeReader.java
index 3bc76b19a..4db6dd70e 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/SubtreeReader.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/SubtreeReader.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import static com.google.common.base.Preconditions.checkArgument;
 
@@ -26,6 +26,7 @@ import io.fd.honeycomb.translate.read.ReadFailedException;
 import io.fd.honeycomb.translate.read.Reader;
 import io.fd.honeycomb.translate.util.RWUtils;
 import io.fd.honeycomb.translate.util.ReflectionUtils;
+import io.fd.honeycomb.translate.util.read.DelegatingReader;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.Collections;
@@ -45,7 +46,7 @@ import org.slf4j.LoggerFactory;
  * Simple Reader delegate for subtree Readers (Readers handling also children nodes) providing a list of all the
  * children nodes being handled.
  */
-class SubtreeReader<D extends DataObject, B extends Builder<D>> implements Reader<D, B> {
+class SubtreeReader<D extends DataObject, B extends Builder<D>> implements DelegatingReader<D, B> {
 
     private static final Logger LOG = LoggerFactory.getLogger(SubtreeReader.class);
 
@@ -103,21 +104,8 @@ class SubtreeReader<D extends DataObject, B extends Builder<D>> implements Reade
     }
 
     @Override
-    public void readCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final B builder,
-                                      @Nonnull final ReadContext ctx)
-            throws ReadFailedException {
-        delegate.readCurrentAttributes(id, builder, ctx);
-    }
-
-    @Nonnull
-    @Override
-    public B getBuilder(final InstanceIdentifier<D> id) {
-        return delegate.getBuilder(id);
-    }
-
-    @Override
-    public void merge(@Nonnull final Builder<? extends DataObject> parentBuilder, @Nonnull final D readValue) {
-        delegate.merge(parentBuilder, readValue);
+    public Reader<D, B> getDelegate() {
+        return delegate;
     }
 
     @Nonnull
@@ -209,7 +197,7 @@ class SubtreeReader<D extends DataObject, B extends Builder<D>> implements Reade
     }
 
     static class SubtreeListReader<D extends DataObject & Identifiable<K>, B extends Builder<D>, K extends Identifier<D>>
-            extends SubtreeReader<D, B> implements ListReader<D, K, B> {
+            extends SubtreeReader<D, B> implements DelegatingListReader<D, K, B>, ListReader<D, K, B> {
 
         final ListReader<D, K, B> delegate;
 
@@ -219,22 +207,9 @@ class SubtreeReader<D extends DataObject, B extends Builder<D>> implements Reade
             this.delegate = delegate;
         }
 
-        @Nonnull
-        @Override
-        public List<D> readList(@Nonnull final InstanceIdentifier<D> id, @Nonnull final ReadContext ctx)
-                throws ReadFailedException {
-            return delegate.readList(id, ctx);
-        }
-
-        @Override
-        public void merge(@Nonnull final Builder<? extends DataObject> builder, @Nonnull final List<D> readData) {
-            delegate.merge(builder, readData);
-        }
-
         @Override
-        public List<K> getAllIds(@Nonnull final InstanceIdentifier<D> id,
-                                 @Nonnull final ReadContext ctx) throws ReadFailedException {
-            return delegate.getAllIds(id, ctx);
+        public ListReader<D, K, B> getDelegate() {
+            return delegate;
         }
     }
 
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/TypeHierarchy.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/TypeHierarchy.java
index a30663221..14fc57632 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/registry/TypeHierarchy.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/read/registry/TypeHierarchy.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import static com.google.common.base.Preconditions.checkArgument;
 
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/write/registry/FlatWriterRegistry.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistry.java
index e5b829d6a..990431a15 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/write/registry/FlatWriterRegistry.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistry.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.write.registry;
+package io.fd.honeycomb.translate.impl.write.registry;
 
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/write/registry/FlatWriterRegistryBuilder.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistryBuilder.java
index 0f75de7e7..936aa3c1e 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/write/registry/FlatWriterRegistryBuilder.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistryBuilder.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.write.registry;
+package io.fd.honeycomb.translate.impl.write.registry;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableMap;
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/write/registry/SubtreeWriter.java b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/SubtreeWriter.java
index bab1da16f..fc6ecc67e 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/write/registry/SubtreeWriter.java
+++ b/infra/translate-impl/src/main/java/io/fd/honeycomb/translate/impl/write/registry/SubtreeWriter.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.write.registry;
+package io.fd.honeycomb.translate.impl.write.registry;
 
 import static com.google.common.base.Preconditions.checkArgument;
 
diff --git a/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/GenericListReaderTest.java b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/GenericListReaderTest.java
index 0dc916fb8..3ed400dba 100644
--- a/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/GenericListReaderTest.java
+++ b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/GenericListReaderTest.java
@@ -25,7 +25,6 @@ import static org.mockito.Mockito.when;
 import com.google.common.collect.Lists;
 import io.fd.honeycomb.translate.read.ReadContext;
 import io.fd.honeycomb.translate.spi.read.ListReaderCustomizer;
-import java.util.Collections;
 import java.util.List;
 import org.junit.Before;
 import org.junit.Test;
@@ -78,7 +77,7 @@ public class GenericListReaderTest {
     @Test
     public void testMerge() throws Exception {
         reader.merge(builder, data);
-        verify(customizer).merge(builder, Collections.singletonList(data));
+        verify(customizer).merge(builder, data);
     }
 
     @Test
diff --git a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/read/registry/CompositeReaderRegistryBuilderTest.java b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistryBuilderTest.java
index d742575be..4dee8e60f 100644
--- a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/read/registry/CompositeReaderRegistryBuilderTest.java
+++ b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistryBuilderTest.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
diff --git a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/read/registry/CompositeReaderRegistryTest.java b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistryTest.java
index 06cb8498f..40068e02c 100644
--- a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/read/registry/CompositeReaderRegistryTest.java
+++ b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderRegistryTest.java
@@ -14,16 +14,16 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import static io.fd.honeycomb.translate.util.DataObjects.DataObject3;
 import static io.fd.honeycomb.translate.util.DataObjects.DataObject3.DataObject31;
 import static io.fd.honeycomb.translate.util.DataObjects.DataObject4;
 import static io.fd.honeycomb.translate.util.DataObjects.DataObject4.DataObject41;
 import static org.mockito.Matchers.any;
+import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.inOrder;
 import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -37,6 +37,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.mockito.InOrder;
 import org.mockito.Mock;
+import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
 import org.opendaylight.yangtools.concepts.Builder;
 import org.opendaylight.yangtools.yang.binding.DataObject;
@@ -57,16 +58,27 @@ public class CompositeReaderRegistryTest {
         MockitoAnnotations.initMocks(this);
 
         reader31 = mockReader(DataObject31.class);
+        final Reader<DataObject3, Builder<DataObject3>> mockedReader3 = mockReader(DataObject3.class);
         rootReader3 =
-                spy(CompositeReader.createForReader(
-                        mockReader(DataObject3.class),
+                Mockito.spy(CompositeReader.createForReader(
+                        mockedReader3,
                         ImmutableMap.of(DataObject31.class, reader31)));
+        // This is a workaround. This functionality is already present in CompositeReader, however when wrapping as spy
+        // null is always returned. That's why we need to explicitly stub the method with its actual implementation.
+        // The problem is that the method is inherited as default method from an interface and mockito's spy seems to
+        // have a problem there
+        doReturn(mockedReader3.getBuilder(InstanceIdentifier.create(DataObject3.class)))
+                .when(rootReader3).getBuilder(any(InstanceIdentifier.class));
 
         reader41 = mockReader(DataObject41.class);
+        final Reader<DataObject4, Builder<DataObject4>> mockedReader4 = mockReader(DataObject4.class);
         rootReader4 =
-                spy(CompositeReader.createForReader(
-                        mockReader(DataObject4.class), ImmutableMap.of(
+                Mockito.spy(CompositeReader.createForReader(
+                        mockedReader4, ImmutableMap.of(
                                 DataObject41.class, reader41)));
+        // Workaround
+        doReturn(mockedReader4.getBuilder(InstanceIdentifier.create(DataObject4.class)))
+                .when(rootReader4).getBuilder(any(InstanceIdentifier.class));
 
         reg = new CompositeReaderRegistry(Lists.newArrayList(rootReader3, rootReader4));
     }
diff --git a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/read/registry/CompositeReaderTest.java b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderTest.java
index 9ae036013..8d4bdadda 100644
--- a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/read/registry/CompositeReaderTest.java
+++ b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/registry/CompositeReaderTest.java
@@ -14,13 +14,13 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import static io.fd.honeycomb.translate.util.DataObjects.DataObject4;
 import static io.fd.honeycomb.translate.util.DataObjects.DataObject4.DataObject41;
 import static io.fd.honeycomb.translate.util.DataObjects.DataObjectK;
 import static io.fd.honeycomb.translate.util.DataObjects.DataObjectKey;
-import static io.fd.honeycomb.translate.util.read.registry.CompositeReaderRegistryTest.mockReader;
+import static io.fd.honeycomb.translate.impl.read.registry.CompositeReaderRegistryTest.mockReader;
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.mock;
diff --git a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/read/registry/SubtreeReaderTest.java b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/registry/SubtreeReaderTest.java
index 799b9553f..d2375e6be 100644
--- a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/read/registry/SubtreeReaderTest.java
+++ b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/registry/SubtreeReaderTest.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -31,6 +31,7 @@ import io.fd.honeycomb.translate.util.DataObjects;
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mock;
+import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
 import org.opendaylight.yangtools.concepts.Builder;
 import org.opendaylight.yangtools.yang.binding.ChildOf;
@@ -49,7 +50,7 @@ public class SubtreeReaderTest {
     @Before
     public void setUp() throws Exception {
         MockitoAnnotations.initMocks(this);
-        doReturn(DataObjects.DataObject4.IID).when(delegate).getManagedDataObjectType();
+        Mockito.doReturn(DataObjects.DataObject4.IID).when(delegate).getManagedDataObjectType();
         doReturn(DataObject1.IID).when(delegateLocal).getManagedDataObjectType();
     }
 
diff --git a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/read/registry/TypeHierarchyTest.java b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/registry/TypeHierarchyTest.java
index 3b3ea3a35..bbccc488b 100644
--- a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/read/registry/TypeHierarchyTest.java
+++ b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/read/registry/TypeHierarchyTest.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.read.registry;
+package io.fd.honeycomb.translate.impl.read.registry;
 
 import static org.hamcrest.CoreMatchers.hasItem;
 import static org.hamcrest.CoreMatchers.hasItems;
diff --git a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/write/registry/FlatWriterRegistryBuilderTest.java b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistryBuilderTest.java
index 7822c8926..3a6767265 100644
--- a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/write/registry/FlatWriterRegistryBuilderTest.java
+++ b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistryBuilderTest.java
@@ -14,11 +14,10 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.write.registry;
+package io.fd.honeycomb.translate.impl.write.registry;
 
 import static org.hamcrest.CoreMatchers.anyOf;
 import static org.hamcrest.CoreMatchers.equalTo;
-import static org.hamcrest.CoreMatchers.hasItems;
 import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.is;
 import static org.junit.Assert.assertEquals;
@@ -40,6 +39,7 @@ import io.fd.honeycomb.translate.write.registry.WriterRegistry;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import org.hamcrest.CoreMatchers;
 import org.junit.Test;
 import org.opendaylight.yangtools.yang.binding.DataObject;
 import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
@@ -171,7 +171,7 @@ public class FlatWriterRegistryBuilderTest {
                 mockWriter(DataObjects.DataObject4.class));
         assertThat(forWriter, instanceOf(SubtreeWriter.class));
         assertThat(((SubtreeWriter<?>) forWriter).getHandledChildTypes().size(), is(3));
-        assertThat(((SubtreeWriter<?>) forWriter).getHandledChildTypes(), hasItems(DataObjects.DataObject4.DataObject41.IID,
+        assertThat(((SubtreeWriter<?>) forWriter).getHandledChildTypes(), CoreMatchers.hasItems(DataObjects.DataObject4.DataObject41.IID,
                 DataObjects.DataObject4.DataObject42.IID, DataObjects.DataObject4.DataObject41.DataObject411.IID));
     }
 
diff --git a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/write/registry/FlatWriterRegistryTest.java b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistryTest.java
index 5566fca47..65742df33 100644
--- a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/write/registry/FlatWriterRegistryTest.java
+++ b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/write/registry/FlatWriterRegistryTest.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.write.registry;
+package io.fd.honeycomb.translate.impl.write.registry;
 
 import static org.hamcrest.CoreMatchers.is;
 import static org.junit.Assert.assertThat;
diff --git a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/write/registry/SubtreeWriterTest.java b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/write/registry/SubtreeWriterTest.java
index 313dd34a8..ff2f83158 100644
--- a/infra/translate-utils/src/test/java/io/fd/honeycomb/translate/util/write/registry/SubtreeWriterTest.java
+++ b/infra/translate-impl/src/test/java/io/fd/honeycomb/translate/impl/write/registry/SubtreeWriterTest.java
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.fd.honeycomb.translate.util.write.registry;
+package io.fd.honeycomb.translate.impl.write.registry;
 
 import static org.hamcrest.CoreMatchers.hasItem;
 import static org.junit.Assert.assertEquals;
@@ -25,6 +25,7 @@ import com.google.common.collect.Sets;
 import io.fd.honeycomb.translate.util.DataObjects;
 import io.fd.honeycomb.translate.write.Writer;
 import java.util.Collections;
+import org.hamcrest.CoreMatchers;
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mock;
@@ -78,7 +79,7 @@ public class SubtreeWriterTest {
 
         assertEquals(writer.getManagedDataObjectType(), forWriter.getManagedDataObjectType());
         assertEquals(1, forWriter.getHandledChildTypes().size());
-        assertThat(forWriter.getHandledChildTypes(), hasItem(DataObjects.DataObject4.DataObject41.DataObject411.IID));
+        assertThat(forWriter.getHandledChildTypes(), CoreMatchers.hasItem(DataObjects.DataObject4.DataObject41.DataObject411.IID));
     }
 
 }
\ No newline at end of file
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());
+    }
 }
diff --git a/infra/translate-utils/pom.xml b/infra/translate-utils/pom.xml
index 1ac453d26..6f01a66fc 100644
--- a/infra/translate-utils/pom.xml
+++ b/infra/translate-utils/pom.xml
@@ -78,4 +78,20 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-jar-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>test-jar</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
 </project>
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/AbstractGenericReader.java b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/AbstractGenericReader.java
index 40c78b3c9..b19b72ecf 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/AbstractGenericReader.java
+++ b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/AbstractGenericReader.java
@@ -56,18 +56,15 @@ public abstract class AbstractGenericReader<D extends DataObject, B extends Buil
                                       @Nonnull final ReadContext ctx) throws ReadFailedException {
         LOG.debug("{}: Reading current: {}", this, id);
         final B builder = getBuilder(id);
-        // The empty value could be cached, but no caching is safer since we call overridden getBuilder each time
-        // and the build could produce something different (even if it shouldn't)
-        final D emptyValue = builder.build();
 
         LOG.trace("{}: Reading current attributes", this);
         readCurrentAttributes(id, builder, ctx);
 
         // Need to check whether anything was filled in to determine if data is present or not.
         final D built = builder.build();
-        final Optional<D> read = built.equals(emptyValue)
-            ? Optional.absent()
-            : Optional.of(built);
+        final Optional<D> read = isPresent(id, built, ctx)
+            ? Optional.of(built)
+            : Optional.absent();
 
         LOG.debug("{}: Current node read successfully. Result: {}", this, read);
         return read;
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/BindingBrokerReader.java b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/BindingBrokerReader.java
index b7a38e97f..e59e642c4 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/BindingBrokerReader.java
+++ b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/BindingBrokerReader.java
@@ -50,6 +50,11 @@ public final class BindingBrokerReader<D extends DataObject, B extends Builder<D
         this.datastoreType = datastoreType;
     }
 
+    @Override
+    public boolean isPresent(final InstanceIdentifier<D> id, final D built, final ReadContext ctx) {
+        throw new UnsupportedOperationException("Not supported");
+    }
+
     @Nonnull
     @Override
     public Optional<? extends DataObject> read(@Nonnull final InstanceIdentifier<? extends DataObject> id,
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/DelegatingReader.java b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/DelegatingReader.java
new file mode 100644
index 000000000..513639610
--- /dev/null
+++ b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/DelegatingReader.java
@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.translate.util.read;
+
+import com.google.common.base.Optional;
+import io.fd.honeycomb.translate.read.ListReader;
+import io.fd.honeycomb.translate.read.ReadContext;
+import io.fd.honeycomb.translate.read.ReadFailedException;
+import io.fd.honeycomb.translate.read.Reader;
+import java.util.List;
+import javax.annotation.Nonnull;
+import org.opendaylight.yangtools.concepts.Builder;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.Identifiable;
+import org.opendaylight.yangtools.yang.binding.Identifier;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+/**
+ * A trait of a delegating reader. Delegates all the calls to its delegate.
+ */
+public interface DelegatingReader<D extends DataObject, B extends Builder<D>> extends Reader<D, B> {
+
+    Reader<D, B> getDelegate();
+
+    @Nonnull
+    default Optional<? extends DataObject> read(@Nonnull final InstanceIdentifier<? extends DataObject> id,
+                                                @Nonnull final ReadContext ctx) throws ReadFailedException {
+        return getDelegate().read(id, ctx);
+    }
+
+    default void readCurrentAttributes(@Nonnull final InstanceIdentifier<D> id,
+                                      @Nonnull final B builder,
+                                      @Nonnull final ReadContext ctx) throws ReadFailedException {
+        getDelegate().readCurrentAttributes(id, builder, ctx);
+    }
+
+    @Nonnull
+    default B getBuilder(final InstanceIdentifier<D> id) {
+        return getDelegate().getBuilder(id);
+    }
+
+    default void merge(@Nonnull final Builder<? extends DataObject> parentBuilder,
+                       @Nonnull final D readValue) {
+        getDelegate().merge(parentBuilder, readValue);
+    }
+
+    @Override
+    default boolean isPresent(InstanceIdentifier<D> id, D built, final ReadContext ctx) throws ReadFailedException {
+        return getDelegate().isPresent(id, built, ctx);
+    }
+
+    @Nonnull
+    default InstanceIdentifier<D> getManagedDataObjectType() {
+        return getDelegate().getManagedDataObjectType();
+    }
+
+    /**
+     * ListReader specific delegating trait.
+     */
+    interface DelegatingListReader<D extends DataObject & Identifiable<K>, K extends Identifier<D>, B extends Builder<D>>
+            extends DelegatingReader<D, B>, ListReader<D, K, B> {
+
+        ListReader<D, K, B> getDelegate();
+
+        @Override
+        default List<K> getAllIds(@Nonnull InstanceIdentifier<D> id, @Nonnull ReadContext ctx)
+                throws ReadFailedException {
+            return getDelegate().getAllIds(id, ctx);
+        }
+
+        @Nonnull
+        @Override
+        default List<D> readList(@Nonnull final InstanceIdentifier<D> id, @Nonnull final ReadContext ctx)
+                throws ReadFailedException {
+            return getDelegate().readList(id, ctx);
+        }
+
+        @Override
+        default void merge(@Nonnull final Builder<? extends DataObject> builder,
+                           @Nonnull final List<D> readData) {
+            getDelegate().merge(builder, readData);
+        }
+
+        @Override
+        default void merge(@Nonnull final Builder<? extends DataObject> parentBuilder, @Nonnull final D readValue) {
+            getDelegate().merge(parentBuilder, readValue);
+        }
+    }
+}
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/KeepaliveReaderWrapper.java b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/KeepaliveReaderWrapper.java
index 5ab9bc59e..9a695a53c 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/KeepaliveReaderWrapper.java
+++ b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/KeepaliveReaderWrapper.java
@@ -18,11 +18,10 @@ package io.fd.honeycomb.translate.util.read;
 
 import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
-import io.fd.honeycomb.translate.read.ReadContext;
-import io.fd.honeycomb.translate.read.Reader;
 import io.fd.honeycomb.translate.MappingContext;
 import io.fd.honeycomb.translate.ModificationCache;
-import io.fd.honeycomb.translate.read.ReadFailedException;
+import io.fd.honeycomb.translate.read.ReadContext;
+import io.fd.honeycomb.translate.read.Reader;
 import java.io.Closeable;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
@@ -40,7 +39,7 @@ import org.slf4j.LoggerFactory;
  * In case a specific error occurs, Keep-alive failure listener gets notified.
  */
 public final class KeepaliveReaderWrapper<D extends DataObject, B extends Builder<D>>
-        implements Reader<D, B>, Runnable, Closeable {
+        implements DelegatingReader<D, B>,Runnable, Closeable {
 
     private static final Logger LOG = LoggerFactory.getLogger(KeepaliveReaderWrapper.class);
 
@@ -73,34 +72,6 @@ public final class KeepaliveReaderWrapper<D extends DataObject, B extends Builde
         scheduledFuture = executor.scheduleWithFixedDelay(this, delayInSeconds, delayInSeconds, TimeUnit.SECONDS);
     }
 
-    @Nonnull
-    public Optional<? extends DataObject> read(@Nonnull final InstanceIdentifier id,
-                                               @Nonnull final ReadContext ctx) throws ReadFailedException {
-        return delegate.read(id, ctx);
-    }
-
-    public void readCurrentAttributes(@Nonnull final InstanceIdentifier<D> id,
-                                      @Nonnull final B builder,
-                                      @Nonnull final ReadContext ctx) throws ReadFailedException {
-        delegate.readCurrentAttributes(id, builder, ctx);
-    }
-
-    @Nonnull
-    public B getBuilder(final InstanceIdentifier<D> id) {
-        return delegate.getBuilder(id);
-    }
-
-    public void merge(@Nonnull final Builder<? extends DataObject> parentBuilder,
-                      @Nonnull final D readValue) {
-        delegate.merge(parentBuilder, readValue);
-    }
-
-    @Nonnull
-    @Override
-    public InstanceIdentifier<D> getManagedDataObjectType() {
-        return delegate.getManagedDataObjectType();
-    }
-
     @Override
     public void run() {
         LOG.trace("Invoking keepalive");
@@ -123,6 +94,11 @@ public final class KeepaliveReaderWrapper<D extends DataObject, B extends Builde
         scheduledFuture.cancel(false);
     }
 
+    @Override
+    public Reader<D, B> getDelegate() {
+        return delegate;
+    }
+
     /**
      * Listener that gets called whenever keepalive fails as expected.
      */
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/ReflexiveReader.java b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/ReflexiveReader.java
deleted file mode 100644
index 2aa35514e..000000000
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/ReflexiveReader.java
+++ /dev/null
@@ -1,57 +0,0 @@
-/*
- * Copyright (c) 2016 Cisco and/or its affiliates.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at:
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.fd.honeycomb.translate.util.read;
-
-import io.fd.honeycomb.translate.read.ReadContext;
-import io.fd.honeycomb.translate.read.ReadFailedException;
-import javax.annotation.Nonnull;
-import org.opendaylight.yangtools.concepts.Builder;
-import org.opendaylight.yangtools.yang.binding.DataObject;
-import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
-
-/**
- * Reader that performs no read operation on its own, just fills in the hierarchy.
- * <p/>
- * Might be slow due to reflection !
- */
-public class ReflexiveReader<C extends DataObject, B extends Builder<C>> extends AbstractGenericReader<C, B> {
-
-    private final ReflexiveReaderCustomizer<C, B> customizer;
-
-    public ReflexiveReader(final InstanceIdentifier<C> identifier, final Class<B> builderClass) {
-        super(identifier);
-        this.customizer = new ReflexiveReaderCustomizer<>(identifier.getTargetType(), builderClass);
-    }
-
-    @Override
-    public void readCurrentAttributes(@Nonnull final InstanceIdentifier<C> id, @Nonnull final B builder,
-                                      @Nonnull final ReadContext ctx)
-            throws ReadFailedException {
-        customizer.readCurrentAttributes(id, builder, ctx);
-    }
-
-    @Nonnull
-    @Override
-    public B getBuilder(final InstanceIdentifier<C> id) {
-        return customizer.getBuilder(id);
-    }
-
-    @Override
-    public void merge(@Nonnull final Builder<? extends DataObject> parentBuilder, @Nonnull final C readValue) {
-        customizer.merge(parentBuilder, readValue);
-    }
-}
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/ReflexiveReaderCustomizer.java b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/ReflexiveReaderCustomizer.java
index 18e6285f3..087873306 100644
--- a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/ReflexiveReaderCustomizer.java
+++ b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/read/ReflexiveReaderCustomizer.java
@@ -33,7 +33,7 @@ import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
 /**
  * Might be slow.
  */
-class ReflexiveReaderCustomizer<C extends DataObject, B extends Builder<C>> extends NoopReaderCustomizer<C, B> {
+public class ReflexiveReaderCustomizer<C extends DataObject, B extends Builder<C>> extends NoopReaderCustomizer<C, B> {
 
     private final Class<C> typeClass;
     private final Class<B> builderClass;
diff --git a/ioam/impl/src/test/java/io/fd/honeycomb/vppioam/impl/VppIoamModuleTest.java b/ioam/impl/src/test/java/io/fd/honeycomb/vppioam/impl/VppIoamModuleTest.java
index 288122fd0..d9176d39d 100644
--- a/ioam/impl/src/test/java/io/fd/honeycomb/vppioam/impl/VppIoamModuleTest.java
+++ b/ioam/impl/src/test/java/io/fd/honeycomb/vppioam/impl/VppIoamModuleTest.java
@@ -27,13 +27,10 @@ import static org.mockito.MockitoAnnotations.initMocks;
 import com.google.inject.Guice;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
-import com.google.inject.multibindings.Multibinder;
 import com.google.inject.name.Named;
 import com.google.inject.testing.fieldbinder.Bind;
 import com.google.inject.testing.fieldbinder.BoundFieldModule;
-import io.fd.honeycomb.translate.util.read.registry.CompositeReaderRegistryBuilder;
-import io.fd.honeycomb.translate.util.write.registry.FlatWriterRegistryBuilder;
-import io.fd.honeycomb.translate.vpp.util.NamingContext;
+import io.fd.honeycomb.translate.impl.write.registry.FlatWriterRegistryBuilder;
 import io.fd.honeycomb.translate.write.WriterFactory;
 import java.util.HashSet;
 import java.util.Set;
@@ -41,11 +38,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mock;
 import org.opendaylight.controller.md.sal.binding.api.DataBroker;
-import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
 
-import io.fd.honeycomb.vppioam.impl.config.VppIoamWriterFactory;
-import io.fd.honeycomb.vppioam.impl.util.JVppIoamProvider;
-import io.fd.vpp.jvpp.ioamtrace.future.FutureJVppIoamtrace;
 import io.fd.vpp.jvpp.ioamtrace.future.FutureJVppIoamtraceFacade;
 import io.fd.vpp.jvpp.JVppRegistry;
 
diff --git a/lisp/lisp2vpp/src/test/java/io/fd/honeycomb/lisp/LispModuleTest.java b/lisp/lisp2vpp/src/test/java/io/fd/honeycomb/lisp/LispModuleTest.java
index 6d1e05ce8..20c6aa3f7 100644
--- a/lisp/lisp2vpp/src/test/java/io/fd/honeycomb/lisp/LispModuleTest.java
+++ b/lisp/lisp2vpp/src/test/java/io/fd/honeycomb/lisp/LispModuleTest.java
@@ -29,8 +29,8 @@ import com.google.inject.name.Named;
 import com.google.inject.testing.fieldbinder.Bind;
 import com.google.inject.testing.fieldbinder.BoundFieldModule;
 import io.fd.honeycomb.translate.read.ReaderFactory;
-import io.fd.honeycomb.translate.util.read.registry.CompositeReaderRegistryBuilder;
-import io.fd.honeycomb.translate.util.write.registry.FlatWriterRegistryBuilder;
+import io.fd.honeycomb.translate.impl.read.registry.CompositeReaderRegistryBuilder;
+import io.fd.honeycomb.translate.impl.write.registry.FlatWriterRegistryBuilder;
 import io.fd.honeycomb.translate.vpp.util.NamingContext;
 import io.fd.honeycomb.translate.write.WriterFactory;
 import java.util.HashSet;
diff --git a/nat/nat2vpp/src/test/java/io/fd/honeycomb/nat/NatModuleTest.java b/nat/nat2vpp/src/test/java/io/fd/honeycomb/nat/NatModuleTest.java
index 774dd6f2a..f69672e15 100644
--- a/nat/nat2vpp/src/test/java/io/fd/honeycomb/nat/NatModuleTest.java
+++ b/nat/nat2vpp/src/test/java/io/fd/honeycomb/nat/NatModuleTest.java
@@ -32,8 +32,8 @@ import com.google.inject.name.Named;
 import com.google.inject.testing.fieldbinder.Bind;
 import com.google.inject.testing.fieldbinder.BoundFieldModule;
 import io.fd.honeycomb.translate.read.ReaderFactory;
-import io.fd.honeycomb.translate.util.read.registry.CompositeReaderRegistryBuilder;
-import io.fd.honeycomb.translate.util.write.registry.FlatWriterRegistryBuilder;
+import io.fd.honeycomb.translate.impl.read.registry.CompositeReaderRegistryBuilder;
+import io.fd.honeycomb.translate.impl.write.registry.FlatWriterRegistryBuilder;
 import io.fd.honeycomb.translate.vpp.util.NamingContext;
 import io.fd.honeycomb.translate.write.WriterFactory;
 import io.fd.vpp.jvpp.snat.future.FutureJVppSnatFacade;
diff --git a/nsh/impl/src/test/java/io/fd/honeycomb/vppnsh/impl/VppNshModuleTest.java b/nsh/impl/src/test/java/io/fd/honeycomb/vppnsh/impl/VppNshModuleTest.java
index 211757474..0da2c1bc4 100644
--- a/nsh/impl/src/test/java/io/fd/honeycomb/vppnsh/impl/VppNshModuleTest.java
+++ b/nsh/impl/src/test/java/io/fd/honeycomb/vppnsh/impl/VppNshModuleTest.java
@@ -31,8 +31,8 @@ import com.google.inject.name.Named;
 import com.google.inject.testing.fieldbinder.Bind;
 import com.google.inject.testing.fieldbinder.BoundFieldModule;
 import io.fd.honeycomb.translate.read.ReaderFactory;
-import io.fd.honeycomb.translate.util.read.registry.CompositeReaderRegistryBuilder;
-import io.fd.honeycomb.translate.util.write.registry.FlatWriterRegistryBuilder;
+import io.fd.honeycomb.translate.impl.read.registry.CompositeReaderRegistryBuilder;
+import io.fd.honeycomb.translate.impl.write.registry.FlatWriterRegistryBuilder;
 import io.fd.honeycomb.translate.vpp.util.NamingContext;
 import io.fd.honeycomb.translate.write.WriterFactory;
 import io.fd.vpp.jvpp.JVppRegistry;
diff --git a/v3po/v3po2vpp/src/test/java/io/fd/honeycomb/translate/v3po/V3poModuleTest.java b/v3po/v3po2vpp/src/test/java/io/fd/honeycomb/translate/v3po/V3poModuleTest.java
index 93453dd22..19aa2c98b 100644
--- a/v3po/v3po2vpp/src/test/java/io/fd/honeycomb/translate/v3po/V3poModuleTest.java
+++ b/v3po/v3po2vpp/src/test/java/io/fd/honeycomb/translate/v3po/V3poModuleTest.java
@@ -30,8 +30,8 @@ import com.google.inject.testing.fieldbinder.Bind;
 import com.google.inject.testing.fieldbinder.BoundFieldModule;
 import io.fd.honeycomb.translate.MappingContext;
 import io.fd.honeycomb.translate.read.ReaderFactory;
-import io.fd.honeycomb.translate.util.read.registry.CompositeReaderRegistryBuilder;
-import io.fd.honeycomb.translate.util.write.registry.FlatWriterRegistryBuilder;
+import io.fd.honeycomb.translate.impl.read.registry.CompositeReaderRegistryBuilder;
+import io.fd.honeycomb.translate.impl.write.registry.FlatWriterRegistryBuilder;
 import io.fd.honeycomb.translate.write.WriterFactory;
 import java.util.HashSet;
 import java.util.Set;
diff --git a/v3po/v3po2vpp/src/test/java/io/fd/honeycomb/translate/v3po/vppstate/VppStateTest.java b/v3po/v3po2vpp/src/test/java/io/fd/honeycomb/translate/v3po/vppstate/VppStateTest.java
index cdb2b0376..cdc352ac5 100644
--- a/v3po/v3po2vpp/src/test/java/io/fd/honeycomb/translate/v3po/vppstate/VppStateTest.java
+++ b/v3po/v3po2vpp/src/test/java/io/fd/honeycomb/translate/v3po/vppstate/VppStateTest.java
@@ -35,7 +35,7 @@ import io.fd.honeycomb.translate.impl.read.GenericReader;
 import io.fd.honeycomb.translate.read.ReadContext;
 import io.fd.honeycomb.translate.read.ReadFailedException;
 import io.fd.honeycomb.translate.read.registry.ReaderRegistry;
-import io.fd.honeycomb.translate.util.read.registry.CompositeReaderRegistryBuilder;
+import io.fd.honeycomb.translate.impl.read.registry.CompositeReaderRegistryBuilder;
 import io.fd.honeycomb.vpp.test.util.NamingContextHelper;
 import io.fd.honeycomb.translate.vpp.util.NamingContext;
 import io.fd.honeycomb.vpp.test.util.FutureProducer;