@Autowired
    private RestHighLevelClient client;
public List<Map<String,Object>> search(String index) {
 List<Map<String,Object>> hitList = new ArrayList();
        try {
            //搜索请求
            SearchRequest request = new SearchRequest(index);
          
            SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
            BoolQueryBuilder boolQueryBuilder = QueryBuilders.boolQuery();
           //查询某字段不为空 
           boolQueryBuilder.must(QueryBuilders.boolQuery().must((QueryBuilders.existsQuery("字段"+  ".keyword"))));
            //查询指定字段
            String[] fields = {"字段1","字段2"};
            sourceBuilder.fetchSource(fields,null);
            //把查询添加放入请求中
            sourceBuilder.query(boolQueryBuilder);
            request.source(sourceBuilder);
            //查询数量
            sourceBuilder.size(10000);
            sourceBuilder.trackTotalHits(true);
            //建立SearchResponse
            SearchResponse response;
          
            response = client.search(request, RequestOptions.DEFAULT);
            //封装查询的信息
            for (SearchHit hit : response.getHits().getHits()) {
                hitList.add(hit.getSourceAsMap());
                log.debug("查询结果:{}", hit.getSourceAsString());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return hitList;
}

主要代码：

String[] fields = {“字段1”,“字段2”};
sourceBuilder.fetchSource(fields,null);