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How to translate Elastic Search query in Java by using the query builder?

I am trying to translate the following elastic search query in Java, using the query builder? Can someone give any ideas of it?
GET <index-name>/_search
{
“size”: 1,
“sort”: [
{
“Date”: {
“order”: “desc”
}
}
]
}

You need to use SortBuilder to sort on fields. Below request will sort Date field in desc order
RestHighLevelClient client = new RestHighLevelClient(restClientBuilder);
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.size(1).sort(new FieldSortBuilder("Date").order(SortOrder.DESC));
SearchRequest searchRequest = new SearchRequest("my-index");
searchRequest.source(searchSourceBuilder);
SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);

Java equivalent of elasticsearch CURL query?

My project had a new reqiurement of migrating all datas which are currently in postresql to elasticsearch. Successfully migrated all my datas, but I am stuck with writing java code to search for some datas in elastic search index.
Sample structure of a hit in index is attached in the below image:
I need to find average of activity.attentionLevel from the index.
I wrote something like below query to find average:
GET proktor-activities/_search
{
"aggs" : {
"avg_attention" : {
"avg" : {
"script" : "Float.parseFloat(doc['activity.attentionLevel.keyword'].value)" }
}
}
}
please help me to find java equivalent code for doing the same.
thanks in advance

Using Elastic's RestHighLevel API would be something like this:
// Create the client
RestHighLevelClient client = new RestHighLevelClient(
RestClient.builder(new HttpHost("localhost", 9200, "http")));
// Specify the aggregation request
SearchRequest searchRequest = new SearchRequest("proktor-activities");
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.aggregation(AggregationBuilders
.avg("avg_attention")
.field("activity.attentionLevel"));
searchRequest.source(searchSourceBuilder);
// Execute the aggreagation with Elasticsearch
SearchResponse response = client.search(searchRequest, RequestOptions.DEFAULT);
// Read the aggregation result
Aggregations aggregations = response.getAggregations();
Avg averageAttention = aggregations.get("avg_attention");
double result = averageAttention.getValue();
client.close(); // get done with the client
More information here.

How to use search_after in Elastic High Level Rest Client for pagination

I am using elastic RestHighLevelClient to talk to ES. I am able to query basic queries. Although i am trying to use teh search_after api to design a paginated api from my front end queries. Although query_after is simple to use in the RestLowLevelClient api, i am not able to figure how to use it in the HighLevel API.
Looks like the lucene api has SearchAfterSortedDocQuery, but i am not able to figure how to use it with the elastic search api. For example: in the code below i initialize SearchAfterSortedDocQuery query but not sure how to use it .
RestHighLevelClient client = ESRestClient.getClient();
SearchRequest searchRequest = new SearchRequest();
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.termQuery("field1",value1));
searchSourceBuilder.query(QueryBuilders.termQuery("field2",value2));
searchSourceBuilder.from(0);
searchSourceBuilder.size(limit);
SortField[] sortFields = new SortField[2];
sortFields[0]= new SortField("field1", SortField.Type.LONG);
sortFields[1]= new SortField("field2", SortField.Type.LONG);
FieldDoc fieldDoc = new FieldDoc(0,0); //Is this correct? how to initialize field doc?
fieldDoc.fields = new Object[2];
fieldDoc.fields[0] = new Long("-156034");
fieldDoc.fields[1] = new Long("2297416849");
SearchAfterSortedDocQuery query = new SearchAfterSortedDocQuery(new Sort(sortFields), fieldDoc);
searchRequest.source(searchSourceBuilder);
searchRequest.indices("index1");
try {
SearchResponse response = client.search(searchRequest, RequestOptions.DEFAULT);
System.out.println(response);
}
catch(IOException e){
System.out.println(e);
}
}

I think instead of you using SearchAfterSortedDocQuery, just set search_after in searchSourceBuilder look like below
searchSourceBuilder.searchAfter(new Object[]{sortAfterValue});
after that use SearchRequest and rest client to get the response
SearchRequest searchRequest = new SearchRequest("index");
searchRequest.types("type");
searchRequest.source(searchSourceBuilder);
SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT)
SearchHits hits = searchResponse.getHits();
final you should keep the last sort value by getSortValues() from hits to go to the next page.
hits.getAt(lastIndex).getSortValues()
Elasticsearch search_after api
hope this help.

ElasticSearch java list unique values of field

Hi I am new to elastic search and not getting how to do it in java i tried googling everywhere i am getting curl solution and i am not so comfortable in converting from curl to java.
I want to list unique values of a field and am using elasticseach6.1.2 and RestHighLevelClient so far my code is :
SearchRequest searchRequest = new SearchRequest(INDEX);
searchRequest.types(TYPE);
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.matchAllQuery());
AggregationBuilder aggregation=AggregationBuilders.missing("agg").field("source");
searchSourceBuilder.aggregation(aggregation);
searchRequest.source(searchSourceBuilder);
SearchResponse searchResponse =restHighLevelClient.search(searchRequest);
Aggregation aggrega = searchResponse.getAggregations().get("source");
StringTerms st = (StringTerms) aggrega;
System.out.println(searchResponse);
Here there is field called source i want to list unique values of that with name source,this code is returning me 5 rows with all fields am sure am doing completely wrong.

Try this for elastic version 6.x
SearchRequest searchRequest = new SearchRequest(INDEX);
searchRequest.types(TYPE);
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.matchAllQuery());
AggregationBuilder aggregation=AggregationBuilders.terms("source_aggs")
.field("source.keyword").size(size)
.order(BucketOrder.count(isAscending));
searchSourceBuilder.aggregation(aggregation);
searchRequest.source(searchSourceBuilder);
SearchResponse searchResponse =restHighLevelClient.search(searchRequest);
Aggregation aggrega = searchResponse.getAggregations().get("source_aggs");
StringTerms st = (StringTerms) aggrega;
System.out.println(searchResponse);

Elasticsearch multiple condition query using java api

There are multiple documents containing around 100 fields each. I'd like to perform a following search trough elasticsearch Java API 5.x:
There are 3 fields I'd like to use for this search i.e.
department
job
name
I'd like to search the return documents that match fields like "department: D1", "department: D2", "job: J1", "job: J2" "name: N1"
I've been trying to do it this way
String[] departments = ["d1","d2","d3"];
String[] jobs = ["j1","j2","j3"];
String[] names = ["n1"];
MultiSearchRequestBuilder requestbuilder;
requestBuilder.add(client.prepareSearch().setQuery(QueryBuilders.termsQuery("department", departments)));
requestBuilder.add(client.prepareSearch().setQuery(QueryBuilders.termsQuery("job", jobs)));
requestBuilder.add(client.prepareSearch().setQuery(QueryBuilders.termsQuery("name", names)));
MultiSearchResponse response = requestBuilder.get();
However the queries are executed as if each was an individual query, i.e. in this example when j3 exists in d4, the document with d4 will be matched aswell
How to perform the search the way I mentioned? I've been trying numerous different queries and nothing seems to work, is there something I am missing?

You don't want to use MultiSearchRequestBuilder, you simply need to combine your three constraints in a bool/filter query:
BoolQueryBuilder query = QueryBuilders.boolQuery()
.filter(QueryBuilders.termsQuery("department", departments))
.filter(QueryBuilders.termsQuery("job", jobs))
.filter(QueryBuilders.termsQuery("name", names));
SearchResponse resp = client.prepareSearch().setQuery(query).get();

For Elasticsearch 5.6.4 of using HighRestClient, add required number of sourcebuilder...
static RestHighLevelClient client = new RestHighLevelClient(RestClient.builder(new HttpHost("localhost", 9200, "http")));
public static void multisearch() throws IOException{
SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
sourceBuilder.query(QueryBuilders.termQuery("name", "vijay1"));
SearchRequest searchRequest = new SearchRequest();
searchRequest.indices("posts-1","posts-2").source(sourceBuilder);
SearchResponse searchResponse = client.search(searchRequest);
RestStatus status = searchResponse.status();
System.out.println(searchResponse.toString());