adapt since annotation for next ditto release;

filter out empty objects when deleting metadata;
add unit test;

Signed-off-by: Stefan <stefan.maute@bosch.io>

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

@@ -58,7 +58,7 @@ public final class DittoHeaderNotSupportedException extends DittoRuntimeExceptio
     /**
      * Definition of an optional JSON field that contains the key of the not supported header.
      *
-     * @since 2.5.0
+     * @since 3.0.0
      */
     static final JsonFieldDefinition<String> JSON_FIELD_NOT_SUPPORTED_HEADER_KEY =
             JsonFieldDefinition.ofString("notSupportedHeaderKey",
@@ -99,7 +99,7 @@ public static DittoHeaderNotSupportedException.Builder newInvalidTypeBuilder(fin
      * @param headerValue the value of the header.
      * @return the builder.
      * @throws NullPointerException if any argument is {@code null}.
-     * @since 2.5.0
+     * @since 3.0.0
      */
     public static DittoHeaderNotSupportedException.Builder newInvalidTypeBuilder(final HeaderDefinition headerDefinition,
             @Nullable final CharSequence headerValue) {
@@ -112,7 +112,7 @@ public static DittoHeaderNotSupportedException.Builder newInvalidTypeBuilder(fin
      * The returned builder is initialized with a default message and a default description.
      *
      * @return the builder.
-     * @since 2.5.0
+     * @since 3.0.0
      */
     public static DittoHeaderNotSupportedException.Builder newBuilder() {
         return new Builder();
@@ -141,7 +141,7 @@ public static DittoHeaderNotSupportedException fromJson(final JsonObject jsonObj
      * Returns the key of the not supported header if known.
      *
      * @return an Optional that either contains the key of the not supported header or is empty if the key is unknown.
-     * @since 2.5.0
+     * @since 3.0.0
      */
     public Optional<String> getNotSupportedHeaderKey() {
         return Optional.ofNullable(notSupportedHeaderKey);
@@ -210,7 +210,7 @@ private Builder(final String headerName, @Nullable final CharSequence headerValu
          *
          * @param notSupportedHeaderKey the key of the not supported header.
          * @return this builder instance for method chaining.
-         * @since 2.5.0
+         * @since 3.0.0
          */
         public Builder withNotSupportedHeaderKey(@Nullable final CharSequence notSupportedHeaderKey) {
             if (null != notSupportedHeaderKey) {

base/model/src/main/java/org/eclipse/ditto/base/model/headers/DittoHeaderDefinition.java

@@ -327,7 +327,7 @@ public enum DittoHeaderDefinition implements HeaderDefinition {
      * Key {@code "get-metadata"}, Java type: {@link String}.
      * </p>
      *
-     * @since 2.5.0
+     * @since 3.0.0
      */
     GET_METADATA("get-metadata", String.class, true, false, HeaderValueValidators.getJsonFieldSelectorValidator()),
 
@@ -337,7 +337,7 @@ public enum DittoHeaderDefinition implements HeaderDefinition {
      * Key {@code "delete-metadata"}, Java type: {@link String}.
      * </p>
      *
-     * @since 2.5.0
+     * @since 3.0.0
      */
     DELETE_METADATA("delete-metadata", String.class, true, false, HeaderValueValidators.getJsonFieldSelectorValidator()),
 
@@ -347,7 +347,7 @@ public enum DittoHeaderDefinition implements HeaderDefinition {
      * Key {@code "ditto-metadata"}, Java type: {@link JsonObject}.
      * </p>
      *
-     * @since 2.5.0
+     * @since 3.0.0
      */
     DITTO_METADATA("ditto-metadata", JsonObject.class, false, true, HeaderValueValidators.getNoOpValidator()),
 
@@ -503,7 +503,7 @@ public enum DittoHeaderDefinition implements HeaderDefinition {
      * @param readFromExternalHeaders whether Ditto reads this header from headers sent by externals.
      * @param writeToExternalHeaders whether Ditto publishes this header to externals.
      */
-    private DittoHeaderDefinition(final String theKey,
+    DittoHeaderDefinition(final String theKey,
             final Class<?> theType,
             final boolean readFromExternalHeaders,
             final boolean writeToExternalHeaders,
@@ -519,7 +519,7 @@ private DittoHeaderDefinition(final String theKey,
      * @param readFromExternalHeaders whether Ditto reads this header from headers sent by externals.
      * @param writeToExternalHeaders whether Ditto publishes this header to externals.
      */
-    private DittoHeaderDefinition(final String theKey,
+    DittoHeaderDefinition(final String theKey,
             final Class<?> theType,
             final Class<?> serializationType,
             final boolean readFromExternalHeaders,

base/model/src/main/java/org/eclipse/ditto/base/model/headers/DittoHeaders.java

@@ -352,7 +352,7 @@ static DittoHeadersBuilder newBuilder(final JsonObject jsonObject) {
      *
      * @return set of {@code JsonPointer}s to get {@code Metadata} for.
      * Changes on the returned set are not reflected back to this DittoHeaders instance.
-     * @since 2.5.0
+     * @since 3.0.0
      */
     Set<JsonPointer> getMetadataFieldsToGet();
 
@@ -361,7 +361,7 @@ static DittoHeadersBuilder newBuilder(final JsonObject jsonObject) {
      *
      * @return set of {@code JsonPointer}s to delete {@code Metadata} for.
      * Changes on the returned set are not reflected back to this DittoHeaders instance.
-     * @since 2.5.0
+     * @since 3.0.0
      */
     Set<JsonPointer> getMetadataFieldsToDelete();
 

base/model/src/main/java/org/eclipse/ditto/base/model/headers/HeaderValueValidators.java

@@ -187,7 +187,7 @@ static ValueValidator getMetadataHeadersValidator() {
      * Returns a validator for checking if a CharSequence represents a {@link org.eclipse.ditto.json.JsonFieldSelector}.
      *
      * @return the validator.
-     * @since 2.5.0
+     * @since 3.0.0
      */
     static ValueValidator getJsonFieldSelectorValidator() {
         return JsonFieldSelectorValidator.getInstance();

base/model/src/main/java/org/eclipse/ditto/base/model/headers/JsonFieldSelectorValidator.java

@@ -24,7 +24,7 @@
  * This validator parses a CharSequence to a {@link org.eclipse.ditto.json.JsonFieldSelector}.
  * If parsing fails, a {@link org.eclipse.ditto.base.model.exceptions.DittoHeaderInvalidException} with detailed description is thrown.
  *
- * @since 2.5.0
+ * @since 3.0.0
  */
 @Immutable
 final class JsonFieldSelectorValidator extends AbstractHeaderValueValidator {

concierge/service/src/main/java/org/eclipse/ditto/concierge/service/common/ConciergeConfig.java

@@ -71,7 +71,7 @@ enum ConciergeConfigValue implements KnownConfigValue {
         /**
          * The default namespace to use for creating things without specified namespace.
          *
-         * @since 2.5.0
+         * @since 3.0.0
          */
         DEFAULT_NAMESPACE("default-namespace", "org.eclipse.ditto");
 

documentation/src/main/resources/pages/ditto/basic-metadata.md

@@ -430,18 +430,18 @@ The `delete-metadata` header expects a comma separated list of metadata `{key}`.
 For example a `PATCH` request to `https://{ditto-instance}/api/2/things/{namespace}:{name}` with HTTP header `delete-metadata`
 and value `features/lamp/properties/color` will remove the complete `color` property from the thing metadata.
 
-<b>Note:</b> When deleting things or parts of a thing like feature properties or attributes, their relative metadata 
+<b>Note:</b> When deleting things or parts of a thing, like feature properties or attributes, their relative metadata 
 is also deleted.
 
 ## Wildcard usage for metadata requests
 
 When working with metadata there are some wildcards which can be used to modify, retrieve or delete metadata.
-The following table gives an overview which Wildcards can be used for what requests.
+The following table gives an overview which Wildcards can be used on top-level for what requests.
 
 | Wildcard                                | PUT/PATCH                                                              | GET                                                                          | DELETE                                                                     |
 |-----------------------------------------|------------------------------------------------------------------------|------------------------------------------------------------------------------|----------------------------------------------------------------------------|
 | `*`                                     | x                                                                      | retrieve all metadata relative to the path                                   | delete all metadata relative to the path                                   |
-| `*/key`                                 | add metadata for the given `key` to all JSON leaves                    | retrieve all metadata with `key`                                             | x                                                                          |
+| `*/key`                                 | add metadata for the given `key` to all JSON leaves                    | retrieve all metadata with `key`                                             | delete all metadata with `key`                                             |
 | `attributes/*/key`                      | add metadata for the given `key` to all attributes                     | retrieve metadata for given `key` from all attributes                        | delete metadata for given `key` from all attributes                        |
 | `features/*/properties/*/key`           | add metadata for the given `key` to all feature properties             | retrieve metadata for given `key` from all feature properties                | delete metadata for given `key` from all feature properties                |
 | `features/*/properties/{property}/key`  | add metadata for the given `key` to all features with a given property | retrieve metadata for given `key` from all features with a specific property | delete metadata for given `key` from all features with a specific property |

things/model/src/main/java/org/eclipse/ditto/things/model/signals/commands/exceptions/MetadataHeadersConflictException.java

@@ -29,7 +29,7 @@
 /**
  * Thrown if metadata of a Thing can't be modified.
  *
- * @since 2.5.0
+ * @since 3.0.0
  */
 @Immutable
 @JsonParsableException(errorCode = MetadataHeadersConflictException.ERROR_CODE)

things/model/src/main/java/org/eclipse/ditto/things/model/signals/commands/exceptions/MetadataNotModifiableException.java

@@ -29,7 +29,7 @@
 /**
  * Thrown if metadata of a Thing can't be modified.
  *
- * @since 2.5.0
+ * @since 3.0.0
  */
 @Immutable
 @JsonParsableException(errorCode = MetadataNotModifiableException.ERROR_CODE)

things/service/src/main/java/org/eclipse/ditto/things/service/persistence/actors/strategies/commands/AbstractThingCommandStrategy.java

@@ -12,7 +12,9 @@
  */
 package org.eclipse.ditto.things.service.persistence.actors.strategies.commands;
 
+import java.util.HashMap;
 import java.util.LinkedHashSet;
+import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 
@@ -23,12 +25,14 @@
 import org.eclipse.ditto.base.model.entity.metadata.MetadataBuilder;
 import org.eclipse.ditto.base.model.entity.metadata.MetadataModelFactory;
 import org.eclipse.ditto.base.model.headers.DittoHeaderDefinition;
+import org.eclipse.ditto.base.model.json.FieldType;
 import org.eclipse.ditto.base.model.signals.WithOptionalEntity;
 import org.eclipse.ditto.base.model.signals.commands.Command;
 import org.eclipse.ditto.internal.utils.headers.conditional.ConditionalHeadersValidator;
 import org.eclipse.ditto.internal.utils.persistentactors.etags.AbstractConditionHeaderCheckingCommandStrategy;
 import org.eclipse.ditto.internal.utils.persistentactors.results.Result;
 import org.eclipse.ditto.internal.utils.persistentactors.results.ResultFactory;
+import org.eclipse.ditto.json.JsonKey;
 import org.eclipse.ditto.json.JsonObject;
 import org.eclipse.ditto.json.JsonPointer;
 import org.eclipse.ditto.json.JsonValue;
@@ -219,8 +223,9 @@ private Optional<Metadata> deleteMetadata(final Metadata existingMetadata,
             final Set<JsonPointer> metadataFieldsToDelete) {
         final MetadataBuilder metadataBuilder = existingMetadata.toBuilder();
         metadataFieldsToDelete.forEach(metadataBuilder::remove);
+        final Metadata metadata = filterOutEmptyObjects(metadataBuilder);
 
-        return Optional.of(metadataBuilder.build());
+        return Optional.of(metadata);
     }
 
     @Override
@@ -268,4 +273,29 @@ private Set<JsonPointer> expandWildcardsInMetadataExpression(final Set<JsonPoint
         return resolvedMetadataPointers;
     }
 
+    private Metadata filterOutEmptyObjects(final MetadataBuilder metadataBuilder) {
+        final Metadata metadata = metadataBuilder.build();
+        final MetadataBuilder newMetadataBuilder = MetadataModelFactory.newMetadataBuilder();
+        final Map<String, JsonValue> leafs = new HashMap<>();
+        getNonEmptyLeafs(JsonPointer.empty(), metadata, leafs);
+        leafs.forEach(newMetadataBuilder::set);
+
+        return newMetadataBuilder.build();
+    }
+
+    private static void getNonEmptyLeafs(final JsonPointer path, final JsonValue entity,
+            final Map<String, JsonValue> leafs) {
+        if (entity.isObject()) {
+            final JsonObject jsonObject = entity.asObject();
+            jsonObject.stream()
+                    .filter(field -> !(field.isMarkedAs(FieldType.SPECIAL) || field.isMarkedAs(FieldType.HIDDEN)))
+                    .forEach(jsonField -> {
+                        final JsonKey key = jsonField.getKey();
+                        getNonEmptyLeafs(path.append(key.asPointer()), jsonField.getValue(), leafs);
+                    });
+        } else {
+            leafs.put(path.toString(), entity);
+        }
+    }
+
 }

things/service/src/main/java/org/eclipse/ditto/things/service/persistence/actors/strategies/commands/MetadataFromCommand.java

@@ -100,7 +100,8 @@ static MetadataFromCommand of(final Command<?> command,
                             final JsonObject mergedJson =
                                     JsonFactory.newObject(entity.asObject(),
                                             existingOrEmptyThing.toJson().get(resourcePath));
-                            return ThingsModelFactory.newThing(existingOrEmptyThing.toJson().setValue(resourcePath, mergedJson));
+                            return ThingsModelFactory.newThing(
+                                    existingOrEmptyThing.toJson().setValue(resourcePath, mergedJson));
                         } else {
                             return ThingsModelFactory.newThing(
                                     existingOrEmptyThing.toJson().setValue(resourcePath, entity));

things/service/src/test/java/org/eclipse/ditto/things/service/persistence/actors/ThingPersistenceActorTest.java

@@ -29,6 +29,7 @@
 import org.eclipse.ditto.base.model.auth.DittoAuthorizationContextType;
 import org.eclipse.ditto.base.model.entity.Revision;
 import org.eclipse.ditto.base.model.entity.metadata.Metadata;
+import org.eclipse.ditto.base.model.entity.metadata.MetadataModelFactory;
 import org.eclipse.ditto.base.model.exceptions.DittoRuntimeException;
 import org.eclipse.ditto.base.model.headers.DittoHeaderDefinition;
 import org.eclipse.ditto.base.model.headers.DittoHeaders;
@@ -1441,8 +1442,7 @@ public void modifyThingWithWildcardInMetadata() {
 
             // modify features with metadata
             underTest.tell(modifyThing, getRef());
-            expectMsgEquals(java.time.Duration.ofSeconds(3600),
-                    ETagTestUtils.modifyThingResponse(thing, thing, headers, false));
+            expectMsgEquals(ETagTestUtils.modifyThingResponse(thing, thing, headers, false));
 
             final var modifiedMetadata = JsonObject.newBuilder()
                     .set("modified", "2022-06-23T06:49:05")
@@ -1487,7 +1487,7 @@ public void retrieveFeaturesMetadataWithGetMetadataHeader() {
             final JsonObject commandJson = getJsonCommand(thing);
             final CreateThing createThing = CreateThing.fromJson(commandJson, dittoHeadersV2);
             underTest.tell(createThing, getRef());
-            expectMsgClass(java.time.Duration.ofSeconds(3600), CreateThingResponse.class);
+            expectMsgClass(CreateThingResponse.class);
 
             // retrieve thing with metadata
             final Metadata expectedMetadata = Metadata.newBuilder()
@@ -1910,6 +1910,44 @@ public void multipleMetadataHeadersResultsInException() {
         }};
     }
 
+    @Test
+    public void testRemovalOfEmptyMetadataAfterDeletion() {
+        final var thing = createThingV2WithRandomId();
+        final var putHeaders = DittoHeaders.newBuilder()
+                .putHeader(DittoHeaderDefinition.PUT_METADATA.getKey(),
+                        "[{\"key\":\"*/modified\",\"value\":\"2022-06-23T06:49:05\"}]")
+                .build();
+        final var modifyThing = ModifyThing.of(getIdOrThrow(thing), thing, null, putHeaders);
+
+        final var deleteHeaders = DittoHeaders.newBuilder()
+                .putHeader(DittoHeaderDefinition.DELETE_METADATA.getKey(), "*/modified")
+                .build();
+        final var modifyThing1 = ModifyThing.of(getIdOrThrow(thing), thing, null, deleteHeaders);
+
+        new TestKit(actorSystem) {{
+            final ActorRef underTest = createPersistenceActorFor(thing);
+
+            // create thing
+            final JsonObject commandJson = getJsonCommand(thing);
+            final CreateThing createThing = CreateThing.fromJson(commandJson, dittoHeadersV2);
+            underTest.tell(createThing, getRef());
+            expectMsgClass(CreateThingResponse.class);
+
+            // modify features with metadata
+            underTest.tell(modifyThing, getRef());
+            expectMsgEquals(ETagTestUtils.modifyThingResponse(thing, thing, putHeaders, false));
+
+            underTest.tell(modifyThing1, getRef());
+            expectMsgEquals(ETagTestUtils.modifyThingResponse(thing.toBuilder().setRevision(2).build(), thing,
+                    deleteHeaders, false));
+
+            // assert that metadata is empty
+            final Metadata expectedEmptyMetadata = MetadataModelFactory.emptyMetadata();
+
+            assertMetadataAsExpected(this, underTest, getIdOrThrow(thing), expectedEmptyMetadata);
+        }};
+    }
+
     private void assertPublishEvent(final ThingEvent<?> event) {
         final ThingEvent<?> msg = pubSubTestProbe.expectMsgClass(ThingEvent.class);
         Assertions.assertThat(msg.toJson())

thingsearch/model/src/main/java/org/eclipse/ditto/thingsearch/model/SearchModelFactory.java

@@ -65,7 +65,7 @@ public static SearchResult newSearchResult(final JsonArray items, final long nex
      * @param lastModified the last modified timestamp.
      * @return the new immutable search results object.
      * @throws NullPointerException if {@code items} is {@code null}.
-     * @since 2.5.0
+     * @since 3.0.0
      */
     public static SearchResult newSearchResult(final JsonArray items, final long nextPageOffset,
             @Nullable final Instant lastModified) {

thingsearch/model/src/main/java/org/eclipse/ditto/thingsearch/model/SearchResult.java

@@ -86,7 +86,7 @@ default SearchResultBuilder toBuilder() {
      * Get the timestamp of the last modification of the search result.
      *
      * @return the timestamp.
-     * @since 2.5.0
+     * @since 3.0.0
      */
     Optional<Instant> getLastModified();
 

thingsearch/model/src/main/java/org/eclipse/ditto/thingsearch/model/SearchResultBuilder.java

@@ -48,7 +48,7 @@ public interface SearchResultBuilder {
      *
      * @param lastModified the timestamp.
      * @return this builder.
-     * @since 2.5.0
+     * @since 3.0.0
      */
     SearchResultBuilder lastModified(@Nullable Instant lastModified);