Method to modify elasticsearch query to get score using hits from query response with elasticsearch spring boot.

search-query-with-score.java

/*****
* Tekraze.com for more
*
*****/

///Imports
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageImpl;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;

import org.springframework.data.elasticsearch.core.ElasticsearchTemplate;
import org.springframework.data.elasticsearch.core.ResultsExtractor;
import org.springframework.data.elasticsearch.core.query.*;

import org.elasticsearch.search.SearchHit;
import org.elasticsearch.action.search.SearchResponse;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;

import static org.elasticsearch.index.query.QueryBuilders.*;


/**
* Method to modify query and get Hit Score, and total hits to get a match score
* Instead of BookDTO , you can replace with your class
* 
* @param query is any query like match query, bool query
* @param the pageable paramter containing pagination properies like page size, page number
**/
Page<BookDTO> bookPage(QueryBuilder query, Pageable pageable) {
    /*We create a query with rquired properties */
        SearchQuery searchQuery = new NativeSearchQueryBuilder()
            .withQuery(query)   // wrap the query we created like match query
            .withPageable(pageable) // if pagination required
            .withIndices(bookIndexName) // rquired name of index to search 
            .withTrackScores(true) // required to get hits and total hits
            .build();
      // THe main logic, it is to modify the results and get hits
    // extracting from response object
      Page<BookDTO> result = elasticsearchTemplate.query(searchQuery, new ResultsExtractor<Page<BookDTO>>() {
            @Override
            public Page<BookDTO> extract(SearchResponse response) {
                List<BookDTO> bookList = new LinkedList<BookDTO>();
                // Modify DTO from helper method with score
                response.getHits().forEach(hit -> bookList.add(bookDTOFromMap(hit, response)));
                // return page of recordds with score as nested property of DTO
                 return new PageImpl<BookDTO>(bookList, pageable, response.getHits().getTotalHits());
            }
        });
        return result;
    }

    /****
    **Helper method to get Matchh Score from Hits and total hits
    ** and append to the DTO propeerty/
    ****/
    BookDTO bookDTOFromMap(SearchHit hit, SearchResponse searchResponse) {
        log.debug("Method to get Book DTO from Book Map");
        // Mapper to map hit object our DDTO
        ObjectMapper objectMapper = new ObjectMapper().registerModule(new JavaTimeModule());
        BookDTO bookDTO = objectMapper.convertValue(hit.getSourceAsMap(), BookDTO.class);
        // The score calculate function
        BigDecimal matchPercentage = new BigDecimal((hit.getScore() / searchResponse.getHits().getMaxScore()) * 100)
                .setScale(2, RoundingMode.UP);
        // set the score to DTO property
        bookDTO.setMatchPercentage(matchPercentage);
        return bookDTO;
    }