HSEARCH-3725 Change GsonProvider so that there's only one implementation

We don't need multiple implementations anymore, and we'll need to
execute complex initialization code to work around a bug in Gson
(google/gson#764).

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/gson/spi/GsonProvider.java

@@ -6,21 +6,52 @@
  */
 package org.hibernate.search.backend.elasticsearch.gson.spi;
 
+import java.util.function.Supplier;
+
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
 
 /**
  * Centralizes the configuration of the Gson objects.
- *
  */
-public interface GsonProvider {
+public final class GsonProvider {
+
+	public static GsonProvider create(Supplier<GsonBuilder> builderBaseSupplier, boolean logPrettyPrinting) {
+		return new GsonProvider( builderBaseSupplier, logPrettyPrinting );
+	}
+
+	private final Gson gson;
+
+	private final Gson gsonNoSerializeNulls;
+
+	private final JsonLogHelper logHelper;
+
+	private GsonProvider(Supplier<GsonBuilder> builderBaseSupplier, boolean logPrettyPrinting) {
+		// Null serialization needs to be enabled to index null fields
+		gson = builderBaseSupplier.get()
+				.serializeNulls()
+				.create();
+
+		gsonNoSerializeNulls = builderBaseSupplier.get()
+				.create();
+
+		logHelper = JsonLogHelper.create( builderBaseSupplier.get(), logPrettyPrinting );
+	}
 
-	Gson getGson();
+	public Gson getGson() {
+		return gson;
+	}
 
 	/**
 	 * @return Same as {@link #getGson()}, but with null serialization turned off.
 	 */
-	Gson getGsonNoSerializeNulls();
+	public Gson getGsonNoSerializeNulls() {
+		return gsonNoSerializeNulls;
+	}
 
-	JsonLogHelper getLogHelper();
+	public JsonLogHelper getLogHelper() {
+		return logHelper;
+	}
 
 }

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/impl/ElasticsearchBackendFactory.java

@@ -20,7 +20,6 @@
 import org.hibernate.search.backend.elasticsearch.client.spi.ElasticsearchClientFactory;
 import org.hibernate.search.backend.elasticsearch.dialect.model.impl.ElasticsearchModelDialect;
 import org.hibernate.search.backend.elasticsearch.dialect.impl.ElasticsearchDialectFactory;
-import org.hibernate.search.backend.elasticsearch.gson.impl.DefaultGsonProvider;
 import org.hibernate.search.backend.elasticsearch.gson.spi.GsonProvider;
 import org.hibernate.search.backend.elasticsearch.logging.impl.Log;
 import org.hibernate.search.backend.elasticsearch.multitenancy.impl.DiscriminatorMultiTenancyStrategy;
@@ -85,7 +84,7 @@ public BackendImplementor<?> create(String name, BackendBuildContext buildContex
 		 * vice-versa, it doesn't need a Gson instance that was specially
 		 * configured for a particular Elasticsearch version.
 		 */
-		GsonProvider defaultGsonProvider = DefaultGsonProvider.create( GsonBuilder::new, logPrettyPrinting );
+		GsonProvider defaultGsonProvider = GsonProvider.create( GsonBuilder::new, logPrettyPrinting );
 
 		Optional<ElasticsearchVersion> configuredVersion = VERSION.get( propertySource );
 

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/impl/ElasticsearchLinkImpl.java

@@ -17,7 +17,6 @@
 import org.hibernate.search.backend.elasticsearch.client.spi.ElasticsearchClientImplementor;
 import org.hibernate.search.backend.elasticsearch.dialect.impl.ElasticsearchDialectFactory;
 import org.hibernate.search.backend.elasticsearch.dialect.protocol.impl.ElasticsearchProtocolDialect;
-import org.hibernate.search.backend.elasticsearch.gson.impl.DefaultGsonProvider;
 import org.hibernate.search.backend.elasticsearch.gson.spi.GsonProvider;
 import org.hibernate.search.backend.elasticsearch.link.impl.ElasticsearchLink;
 import org.hibernate.search.backend.elasticsearch.logging.impl.Log;
@@ -105,7 +104,7 @@ void onStart(ConfigurationPropertySource propertySource) {
 			}
 
 			ElasticsearchProtocolDialect protocolDialect = dialectFactory.createProtocolDialect( elasticsearchVersion );
-			gsonProvider = DefaultGsonProvider.create( protocolDialect::createGsonBuilderBase, logPrettyPrinting );
+			gsonProvider = GsonProvider.create( protocolDialect::createGsonBuilderBase, logPrettyPrinting );
 			jsonSyntaxHelper = protocolDialect.createJsonSyntaxHelper();
 			workBuilderFactory = protocolDialect.createWorkBuilderFactory( gsonProvider );
 			searchResultExtractorFactory = protocolDialect.createSearchResultExtractorFactory();

integrationtest/backend/elasticsearch/src/test/java/org/hibernate/search/integrationtest/backend/elasticsearch/client/ElasticsearchContentLengthIT.java

@@ -29,7 +29,7 @@
 import org.hibernate.search.backend.elasticsearch.client.spi.ElasticsearchClientImplementor;
 import org.hibernate.search.backend.elasticsearch.client.spi.ElasticsearchRequest;
 import org.hibernate.search.backend.elasticsearch.client.spi.ElasticsearchResponse;
-import org.hibernate.search.backend.elasticsearch.gson.impl.DefaultGsonProvider;
+import org.hibernate.search.backend.elasticsearch.gson.spi.GsonProvider;
 import org.hibernate.search.backend.elasticsearch.util.spi.URLEncodedString;
 import org.hibernate.search.engine.cfg.spi.ConfigurationPropertySource;
 import org.hibernate.search.engine.environment.bean.BeanHolder;
@@ -185,7 +185,7 @@ private ElasticsearchClientImplementor createClient() {
 		try ( BeanHolder<ElasticsearchClientFactory> factoryHolder =
 				beanResolver.resolve( ElasticsearchClientFactoryImpl.REFERENCE ) ) {
 			return factoryHolder.get().create(
-					backendProperties, DefaultGsonProvider.create( GsonBuilder::new, true )
+					backendProperties, GsonProvider.create( GsonBuilder::new, true )
 			);
 		}
 	}

util/internal/integrationtest/backend/elasticsearch/src/main/java/org/hibernate/search/util/impl/integrationtest/backend/elasticsearch/rule/TestElasticsearchClient.java

@@ -25,7 +25,7 @@
 import org.hibernate.search.backend.elasticsearch.client.spi.ElasticsearchClientImplementor;
 import org.hibernate.search.backend.elasticsearch.client.spi.ElasticsearchRequest;
 import org.hibernate.search.backend.elasticsearch.client.spi.ElasticsearchResponse;
-import org.hibernate.search.backend.elasticsearch.gson.impl.DefaultGsonProvider;
+import org.hibernate.search.backend.elasticsearch.gson.spi.GsonProvider;
 import org.hibernate.search.backend.elasticsearch.impl.ElasticsearchIndexNameNormalizer;
 import org.hibernate.search.backend.elasticsearch.logging.impl.ElasticsearchRequestFormatter;
 import org.hibernate.search.backend.elasticsearch.logging.impl.ElasticsearchResponseFormatter;
@@ -491,7 +491,7 @@ private void before() {
 		try ( BeanHolder<ElasticsearchClientFactory> factoryHolder =
 				beanResolver.resolve( ElasticsearchClientFactoryImpl.REFERENCE ) ) {
 			client = factoryHolder.get().create(
-					backendProperties, DefaultGsonProvider.create( GsonBuilder::new, true )
+					backendProperties, GsonProvider.create( GsonBuilder::new, true )
 			);
 		}
 	}