# How to integrate knnsearch In java application **URL:** \ **Category:** Elasticsearch\ **Tags:** language-clients\ **Created:** [March 5, 2022, 8:49pm UTC](https://discuss.elastic.co/t/how-to-integrate-knnsearch-in-java-application/298897 "2022-03-05T20:49:44Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![dileepkotte4529](https://avatars.discourse-cdn.com/v4/letter/d/f04885/32.png) [@dileepkotte4529](https://discuss.elastic.co/u/dileepkotte4529)\ **Post date:** [March 5, 2022, 8:49pm UTC](https://discuss.elastic.co/t/how-to-integrate-knnsearch-in-java-application/298897/1 "2022-03-05T20:49:44Z")
Hi Folks , I was tried knnsearch for vector similarity search in python it worked .But Now i need to integrate that with my spring application , I don't see much resource on it. But i tried with below code ```auto Elastic Search : 8.0.1 RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200)).build(); ElasticsearchTransport transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); ElasticsearchClient client = new ElasticsearchClient(transport); KnnSearchQuery query = new KnnSearchQuery.Builder().field("image-vector").k(1).numCandidates(100).queryVector(v).build(); KnnSearchRequest request = new KnnSearchRequest.Builder().knn(query).index("image_similarity_1million").fields("humanid").build(); client.knnSearch(request,RequestOptions.DEFAULT); ``` But i am getting exceptions ```auto Exception in thread "main" jakarta.json.JsonException: Jackson exception at co.elastic.clients.json.jackson.JacksonUtils.convertException(JacksonUtils.java:39) at co.elastic.clients.json.jackson.JacksonJsonpMapper$JacksonValueParser.deserialize(JacksonJsonpMapper.java:113) at co.elastic.clients.json.JsonpDeserializer.deserialize(JsonpDeserializer.java:75) at co.elastic.clients.json.JsonpMapperBase.deserialize(JsonpMapperBase.java:41) at co.elastic.clients.json.AttributedJsonpMapper.deserialize(AttributedJsonpMapper.java:45) at co.elastic.clients.json.JsonpDeserializer$1.deserialize(JsonpDeserializer.java:98) at co.elastic.clients.json.NamedDeserializer.deserialize(NamedDeserializer.java:64) at co.elastic.clients.json.ObjectDeserializer$FieldObjectDeserializer.deserialize(ObjectDeserializer.java:72) at co.elastic.clients.json.ObjectDeserializer.deserialize(ObjectDeserializer.java:176) at co.elastic.clients.json.ObjectDeserializer.deserialize(ObjectDeserializer.java:137) at co.elastic.clients.json.ObjectBuilderDeserializer.deserialize(ObjectBuilderDeserializer.java:85) at co.elastic.clients.json.JsonpDeserializerBase$ArrayDeserializer.deserialize(JsonpDeserializerBase.java:320) at co.elastic.clients.json.JsonpDeserializerBase$ArrayDeserializer.deserialize(JsonpDeserializerBase.java:285) at co.elastic.clients.json.JsonpDeserializer.deserialize(JsonpDeserializer.java:75) at co.elastic.clients.json.ObjectDeserializer$FieldObjectDeserializer.deserialize(ObjectDeserializer.java:72) at co.elastic.clients.json.ObjectDeserializer.deserialize(ObjectDeserializer.java:176) at co.elastic.clients.json.ObjectDeserializer.deserialize(ObjectDeserializer.java:137) at co.elastic.clients.json.JsonpDeserializer.deserialize(JsonpDeserializer.java:75) at co.elastic.clients.json.ObjectBuilderDeserializer.deserialize(ObjectBuilderDeserializer.java:79) at co.elastic.clients.json.ObjectDeserializer$FieldObjectDeserializer.deserialize(ObjectDeserializer.java:72) at co.elastic.clients.json.ObjectDeserializer.deserialize(ObjectDeserializer.java:176) at co.elastic.clients.json.ObjectDeserializer.deserialize(ObjectDeserializer.java:137) at co.elastic.clients.json.JsonpDeserializer.deserialize(JsonpDeserializer.java:75) at co.elastic.clients.json.ObjectBuilderDeserializer.deserialize(ObjectBuilderDeserializer.java:79) at co.elastic.clients.json.DelegatingDeserializer$SameType.deserialize(DelegatingDeserializer.java:43) at co.elastic.clients.transport.endpoints.EndpointWithResponseMapperAttr$1.deserialize(EndpointWithResponseMapperAttr.java:56) at co.elastic.clients.transport.rest_client.RestClientTransport.decodeResponse(RestClientTransport.java:328) at co.elastic.clients.transport.rest_client.RestClientTransport.getHighLevelResponse(RestClientTransport.java:294) at co.elastic.clients.transport.rest_client.RestClientTransport.performRequest(RestClientTransport.java:147) at co.elastic.clients.elasticsearch.ElasticsearchClient.knnSearch(ElasticsearchClient.java:1010) at Elastic.main(Elastic.java:37) Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `HUMAN` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator) at [Source: (org.apache.http.nio.entity.ContentInputStream); line: 1, column: 250] at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:67) at com.fasterxml.jackson.databind.DeserializationContext.reportBadDefinition(DeserializationContext.java:1764) at com.fasterxml.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:400) at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1209) at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1400) at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:362) at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:195) at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:322) at com.fasterxml.jackson.databind.ObjectMapper._readValue(ObjectMapper.java:4569) at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2798) at co.elastic.clients.json.jackson.JacksonJsonpMapper$JacksonValueParser.deserialize(JacksonJsonpMapper.java:111) ... 29 more ``` please help me out. ---
**Author:** ![Julie\_Tibshirani](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/julie_tibshirani/32/55628_2.png) [@Julie\_Tibshirani](https://discuss.elastic.co/u/Julie_Tibshirani)\ **Post date:** [March 9, 2022, 6:32pm UTC](https://discuss.elastic.co/t/how-to-integrate-knnsearch-in-java-application/298897/2 "2022-03-09T18:32:54Z")
Hi @dileepkotte4529 , great that you are trying out the kNN search API. I am not a Spring expert, so apologies if this is not helpful, but it looks like one of your classes called HUMAN is missing some methods required to construct it: ```auto Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `HUMAN` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator) ``` I don't see any Elasticsearch-specific issues in the stack trace. Julie ---
**Author:** ![swallez](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/swallez/32/11972_2.png) [@swallez](https://discuss.elastic.co/u/swallez)\ **Post date:** [March 10, 2022, 10:20am UTC](https://discuss.elastic.co/t/how-to-integrate-knnsearch-in-java-application/298897/3 "2022-03-10T10:20:28Z")
This line is a High Level Rest Client call: `client.knnSearch(request,RequestOptions.DEFAULT);` I guess your actual code is more like `client.knnSearch(request, SomeDocumentClass.class);` where `SomeApplicationClass` is the type to use to deserialize documents returned by the search request. The error indicates that Jackson is unable to create an instance of `HUMAN`. What does the definition of your `SomeDocumentClass` look like? ---
**Author:** ![dileepkotte4529](https://avatars.discourse-cdn.com/v4/letter/d/f04885/32.png) [@dileepkotte4529](https://discuss.elastic.co/u/dileepkotte4529)\ **Post date:** [March 10, 2022, 10:45am UTC](https://discuss.elastic.co/t/how-to-integrate-knnsearch-in-java-application/298897/4 "2022-03-10T10:45:19Z")
Yeah ! Actually I fixed that day itself . Thank you for response @swallez @Julie_Tibshirani ---
**Author:** ![swallez](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/swallez/32/11972_2.png) [@swallez](https://discuss.elastic.co/u/swallez)\ **Post date:** [March 10, 2022, 2:33pm UTC](https://discuss.elastic.co/t/how-to-integrate-knnsearch-in-java-application/298897/5 "2022-03-10T14:33:11Z")
Awesome! Thanks for the update @dileepkotte4529! ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [April 7, 2022, 2:33pm UTC](https://discuss.elastic.co/t/how-to-integrate-knnsearch-in-java-application/298897/6 "2022-04-07T14:33:27Z")
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