最开始做ES的时候，只是做单纯做查询，后续由于业务规则，涉及到组合复杂查询，去研究了一下ES，最主要的是BoolQueryBuilderl该类的使用--must和should方法。
这里介绍一下主要几个类：
RestHighLevelClient --rest高级客户端，主方法:search(),主参数:SearchRequest,RequestOptions
SearchRequest --查询主类，主方法:source()主资源方法，主参数：SearchSourceBuilder
SearchSourceBuilder --查询主类，主要方法:query()查询条件的拼装,参数:QueryBuilder；from(),size()分页方法；sort()排序方法，参数：SortBuilder<?>
完整代码如下：
SearchRequest searchRequest = new SearchRequest(index);
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
BoolQueryBuilder mustBuilder = new BoolQueryBuilder();
BoolQueryBuilder shouldBuilder = new BoolQueryBuilder();
shouldBuilder.should(QueryBuilders.termQuery("a", esChatMessageReq.getUserId()));
shouldBuilder.should(QueryBuilders.termQuery("b", esChatMessageReq.getUserId()));
mustBuilder.must(QueryBuilders.matchQuery("c", esChatMessageReq.getMerCode())).must(shouldBuilder);
searchSourceBuilder.query(mustBuilder);
searchSourceBuilder.from((esChatMessageReq.getCurrentPage() - 1) * esChatMessageReq.getPageSize());
searchSourceBuilder.size(esChatMessageReq.getPageSize());
searchSourceBuilder.sort(new FieldSortBuilder("timeStamp").unmappedType("long").order(SortOrder.DESC));
searchRequest.source(searchSourceBuilder);
SearchResponse searchResponse = restHighLevelClient.search(searchRequest, RequestOptions.DEFAULT);
解析es数据：
SearchHits hits = searchResponse.getHits();
for (SearchHit searchHit : hits.getHits()) {
String result = searchHit.getSourceAsString();
}