Resolve "Die Statistiken sollten auch in ElasticSearch hinterlegt werden."

Related to #384 (closed)

src/main/java/at/ac/uibk/gitsearch/config/ElasticsearchConfiguration.java

@@ -4,8 +4,10 @@ import co.elastic.clients.elasticsearch.ElasticsearchClient;
 import co.elastic.clients.json.jackson.JacksonJsonpMapper;
 import co.elastic.clients.transport.ElasticsearchTransport;
 import co.elastic.clients.transport.rest_client.RestClientTransport;
+import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.databind.DeserializationContext;
 import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.SerializerProvider;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 import java.io.IOException;
 import java.net.MalformedURLException;
@@ -148,12 +150,26 @@ public class ElasticsearchConfiguration extends ElasticsearchConfigurationSuppor
         }
     }
 
+    public static class InstantTimeConverter extends com.fasterxml.jackson.databind.JsonSerializer<Instant> {
+
+        @SuppressWarnings("unused")
+        private final Logger log = LogManager.getLogger(MoreRobustLocalDateTimeConverter.class);
+
+        @Override
+        public void serialize(Instant value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
+            String s = value.toString();
+            gen.writeString(s);
+        }
+    }
+
     @Bean
     public ElasticsearchClient getElasticsearchAPIClient() throws MalformedURLException {
         // Create the transport with a Jackson mapper
         final JacksonJsonpMapper mapper = new JacksonJsonpMapper();
+
         final JavaTimeModule timeModule = new JavaTimeModule();
         timeModule.addDeserializer(LocalDateTime.class, new ElasticsearchConfiguration.MoreRobustLocalDateTimeConverter());
+        timeModule.addSerializer(Instant.class, new ElasticsearchConfiguration.InstantTimeConverter());
 
         mapper.objectMapper().registerModule(timeModule);
         mapper.objectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);