網上搜到批量查詢可以通過TransportClient實現，但官方推薦使用RestHighLevelClient實現

注意：

We plan on deprecating the TransportClient in Elasticsearch 7.0 and removing it completely in 8.0. Instead, you should be using the Java High Level REST Client, which executes HTTP requests rather than serialized Java requests.

查詢最新的RestHighLevelClient api文件

MultiSearchRequest request = new MultiSearchRequest();    
SearchRequest firstSearchRequest = new SearchRequest();   
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.matchQuery("user", "kimchy"));
firstSearchRequest.source(searchSourceBuilder);
request.add(firstSearchRequest);                          
SearchRequest secondSearchRequest 
 
= new SearchRequest();  
searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.matchQuery("user", "luca"));
secondSearchRequest.source(searchSourceBuilder);
request.add(secondSearchRequest);
MultiSearchResponse response = client.msearch(request, RequestOptions.DEFAULT);

但嘗試發現，沒有msearch這個方法，發現版本為6.1的 不支援這個方法

SearchRequestBuilder srb1 = client
    .prepareSearch().setQuery(QueryBuilders.queryStringQuery("elasticsearch")).setSize(1);
SearchRequestBuilder srb2 = client
    .prepareSearch().setQuery(QueryBuilders.matchQuery("name", "kimchy")).setSize(1);

MultiSearchResponse sr = client.prepareMultiSearch()
        .add(srb1)
        .add(srb2)
        .get();

// You will get all individual responses from MultiSearchResponse#getResponses()
long nbHits = 0;
for (MultiSearchResponse.Item item : sr.getResponses()) {
    SearchResponse response = item.getResponse();
    nbHits += response.getHits().getTotalHits();
}

只能使用TransportClient來實現

import java.io.IOException;
import java.net.InetAddress;

import org.elasticsearch.action.search.MultiSearchResponse;
import org.elasticsearch.action.search.MultiSearchResponse.Item;
import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.client.transport.TransportClient;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.transport.TransportAddress;
import org.elasticsearch.search.builder.SearchSourceBuilder;
import org.elasticsearch.transport.client.PreBuiltTransportClient;

public class App4 {
    @SuppressWarnings("resource")
    public static void main(String[] args) throws IOException {
             
            TransportClient client=new PreBuiltTransportClient(Settings.EMPTY)
                    .addTransportAddress(new TransportAddress(InetAddress.getByName("127.0.0.1"), 9300)); //1st ES Node host and port
            SearchRequest req=new SearchRequest("person");
             SearchSourceBuilder builder=new SearchSourceBuilder();
             builder.size(10);
             req.source(builder);
             
             SearchRequest req1=new SearchRequest("posts");
             SearchSourceBuilder builder1=new SearchSourceBuilder();
             builder.size(10);
             req.source(builder1);
            MultiSearchResponse bulkResponse=client.prepareMultiSearch()
                    .add(req)
                    .add(req1)
                    .get();
            
            for (Item item : bulkResponse.getResponses()) {
                if (item.isFailure()) { 
                    System.out.println(item.getFailureMessage());
                }else {
                    System.out.println("-----------------------------------------------------------------------");
                    System.out.println(item.getResponse().toString());
                }
            }
         
        /**** Done ****/
        System.out.println("Done");

    }
    
}