ElasticSearch(JAVA) LowLevelClient

• JSON형식 그대로의 쿼리를 하고 싶어서 찾아보던 중 LowLevelClient는 JSON형식 그대로 쿼리가 가능하다는 것을 알고 공부하게 되었다.
• LowlevelClient 와 HighLevelClient Query 차이

String hostname ="10.10.~.~";
    int port = 9200;
    String scheme = "http";
    HttpHost host = new HttpHost(hostname, port, scheme);
    RestClientBuilder restClientBuilder = RestClient.builder(host);

		//HighLevel Client
    RestHighLevelClient client = new RestHighLevelClient(restClientBuilder);

    //lowLevelClient
    RestClient lowLevelClient = restClientBuilder.build();

//==========================LowLevelClient================================
public void LowlevelClientQuery(){
        Map<String,String> params = Collections.emptyMap();
        String query ="{\\"query\\": {\\n" +
                "        \\"match_all\\":{}\\n" +
                "    }\\n" +
                "}";

        try {
            Request request = new Request("GET","/indexName/_search");
            request.setJsonEntity(query);
            Response response = lowLevelClient.performRequest(request);

            InputStreamReader reader = new InputStreamReader(response.getEntity().getContent());
            Stream<String> stream = new BufferedReader(reader).lines();
            String streamToString = stream.collect(Collectors.joining());

            JSONParser jsonParser = new JSONParser();
            Object obj = jsonParser.parse(streamToString);
            JSONObject jsonObject = (JSONObject) obj;
            JSONObject getHits = (JSONObject) jsonObject.get("hits");
            JSONArray hits = (JSONArray) getHits.get("hits");
            System.out.println(hits);

        } catch (IOException | ParseException e) {
            throw new RuntimeException(e);
        }

    }

//==========================HighLevelClient================================
public List<Map<String,Object>> HighLevelClientQuery(){
        List<Map<String,Object>> rules = new ArrayList<Map<String,Object>>();
        String indexName = "indexName";
        SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
        searchSourceBuilder.query(
                QueryBuilders.matchAllQuery()
        );
        searchSourceBuilder.size(1000);
        try {
            SearchRequest request = new SearchRequest(indexName);
            request.source(searchSourceBuilder);
            SearchResponse response = client.search(request, RequestOptions.DEFAULT);
            SearchHits searchHits = response.getHits();
            for(SearchHit hit : searchHits){
                Map<String, Object> result = hit.getSourceAsMap();
                rules.add(result);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        return rules;
    }