add @nullable annotations to some variables and methods;

extend javadoc;

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

thingsearch/service/src/main/java/org/eclipse/ditto/thingsearch/service/common/config/DittoSearchConfig.java

@@ -46,9 +46,9 @@ public final class DittoSearchConfig implements SearchConfig, WithConfigPath {
 
     private final DittoServiceConfig dittoServiceConfig;
     @Nullable private final String mongoHintsByNamespace;
-    private final String queryCriteriaValidator;
-    private final String searchUpdateMapper;
-    private final String searchUpdateObserver;
+    @Nullable private final String queryCriteriaValidator;
+    @Nullable private final String searchUpdateMapper;
+    @Nullable private final String searchUpdateObserver;
     private final UpdaterConfig updaterConfig;
     private final HealthCheckConfig healthCheckConfig;
     private final IndexInitializationConfig indexInitializationConfig;
@@ -88,16 +88,19 @@ public Optional<String> getMongoHintsByNamespace() {
         return Optional.ofNullable(mongoHintsByNamespace);
     }
 
+    @Nullable
     @Override
     public String getQueryValidatorImplementation() {
         return queryCriteriaValidator;
     }
 
+    @Nullable
     @Override
     public String getSearchUpdateMapperImplementation() {
         return searchUpdateMapper;
     }
 
+    @Nullable
     @Override
     public String getSearchUpdateObserverImplementation() {
         return searchUpdateObserver;

thingsearch/service/src/main/java/org/eclipse/ditto/thingsearch/service/common/config/SearchConfig.java

@@ -14,6 +14,7 @@
 
 import java.util.Optional;
 
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
 import org.eclipse.ditto.base.service.config.ServiceSpecificConfig;
@@ -37,22 +38,25 @@ public interface SearchConfig extends ServiceSpecificConfig, WithHealthCheckConf
      * {@link org.eclipse.ditto.rql.query.criteria.Criteria} of a
      * {@link org.eclipse.ditto.thingsearch.model.signals.commands.query.ThingSearchQueryCommand}.
      *
-     * @return the config.
+     * @return the query validator implementation or {@code null}.
      */
+    @Nullable
     String getQueryValidatorImplementation();
 
     /**
      * Returns the {@code SearchUpdateMapper} to be used for additional processing of search updates.
      *
-     * @return the config.
+     * @return the search update mapper implementation or {@code null}.
      */
+    @Nullable
     String getSearchUpdateMapperImplementation();
 
     /**
      * Returns the {@code SearchUpdateObserver} to be used for additional processing of search updates.
      *
-     * @return the name of the implementing class.
+     * @return the name of the implementing class or {@code null}.
      */
+    @Nullable
     String getSearchUpdateObserverImplementation();
 
     /**

thingsearch/service/src/main/java/org/eclipse/ditto/thingsearch/service/updater/actors/DefaultSearchUpdateObserver.java

@@ -12,6 +12,8 @@
  */
 package org.eclipse.ditto.thingsearch.service.updater.actors;
 
+import javax.annotation.Nullable;
+
 import org.eclipse.ditto.json.JsonObject;
 import org.eclipse.ditto.thingsearch.service.persistence.write.model.Metadata;
 
@@ -27,7 +29,7 @@ public DefaultSearchUpdateObserver(final ActorSystem system) {
     }
 
     @Override
-    public void process(final Metadata metadata, final JsonObject thingJson) {
+    public void process(final Metadata metadata, @Nullable final JsonObject thingJson) {
         // noop
     }
 }

thingsearch/service/src/main/java/org/eclipse/ditto/thingsearch/service/updater/actors/SearchUpdateObserver.java

@@ -42,17 +42,18 @@ public abstract class SearchUpdateObserver implements Extension {
     /**
      * Load a {@code SearchUpdateObserver} dynamically according to the search configuration.
      *
-     * @param actorSystem The actor system in which to load the observer.
-     * @return The thing event observer.
+     * @param actorSystem the actor system in which to load the observer.
+     * @return the thing event observer.
      */
     public static SearchUpdateObserver get(final ActorSystem actorSystem) {
         return EXTENSION_ID.get(actorSystem);
     }
 
     /**
-     * Process the given {@code ThingEvent}.
+     * Process the given {@code Metadata} and thing as {@code JsonObject}.
      *
-     * @param metadata the thing event
+     * @param metadata the metadata for the update.
+     * @param thingJson the thing used for the update as jsonObject.
      */
     public abstract void process(final Metadata metadata, @Nullable final JsonObject thingJson);
 

thingsearch/service/src/main/java/org/eclipse/ditto/thingsearch/service/updater/actors/ThingUpdater.java

@@ -251,7 +251,7 @@ private Metadata exportMetadataWithSender(final boolean shouldAcknowledge,
     /**
      * Push metadata of this updater to the queue of thing-changes to be streamed into the persistence.
      *
-     * @param updateReason TODO
+     * @param updateReason the reason why the search index is updated.
      */
     private void enqueueMetadata(final UpdateReason updateReason) {
         enqueueMetadata(exportMetadata(null, null).withUpdateReason(updateReason));