简单查询

简单的查询语句可以采用 RestHighLevelClient 拼SearchSourceBuilder方式。

SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.size(10);
SearchRequest searchRequest = new SearchRequest(index);
searchRequest.source(searchSourceBuilder);
SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);

响应结果 SearchRespone

通过执行搜索返回的SearchResponse提供了有关搜索执行本身的详细信息以及对返回文档的访问。首先，有关于请求执行本身的有用信息，如HTTP状态代码、执行时间或请求是否提前终止或超时：

RestStatus status = searchResponse.status();
TimeValue took = searchResponse.getTook();
Boolean terminatedEarly = searchResponse.isTerminatedEarly();
boolean timedOut = searchResponse.isTimedOut();

其次，SearchResponse还提供了分片总数以及成功分片与失败分片的统计信息，提供分片级别的执行信息。也可以通过ShardSearchFailures数组迭代处理可能的故障，如下例所示：

int totalShards = searchResponse.getTotalShards();
int successfulShards = searchResponse.getSuccessfulShards();
int failedShards = searchResponse.getFailedShards();
for (ShardSearchFailure failure : searchResponse.getShardFailures()) {
    // failures should be handled here
}

取出结果

SearchHits hits = searchResponse.getHits();
long totalHits = hits.getTotalHits();
float maxScore = hits.getMaxScore();
SearchHit[] searchHits = hits.getHits();
for (SearchHit hit : searchHits) {
    // do something with the SearchHit
}

SearchHit提供对基本信息的访问，如索引、类型、docId和每次搜索命中的分数：

String index = hit.getIndex();
String type = hit.getType();
String id = hit.getId();
float score = hit.getScore();

此外，它还允许您以简单的JSON字符串或键/值对映射的形式获取文档源。在此映射中，常规字段由字段名称设置关键帧，并包含字段值。多值字段作为对象列表返回，嵌套对象作为另一个键/值映射返回。这些情况需要进行相应处理：

String sourceAsString = hit.getSourceAsString();
Map<String, Object> sourceAsMap = hit.getSourceAsMap();
String documentTitle = (String) sourceAsMap.get("title");
List<Object> users = (List<Object>) sourceAsMap.get("user");
Map<String, Object> innerObject =
        (Map<String, Object>) sourceAsMap.get("innerObject");

高亮处理

如果请求，可以从结果中的每个SearchHit检索突出显示的文本片段。命中对象提供对HighlightField实例的字段名称映射的访问，每个实例包含一个或多个突出显示的文本片段

SearchHits hits = searchResponse.getHits();
for (SearchHit hit : hits.getHits()) {
    Map<String, HighlightField> highlightFields = hit.getHighlightFields();
    HighlightField highlight = highlightFields.get("title"); 
    Text[] fragments = highlight.fragments();  
    String fragmentString = fragments[0].string();
}

取出聚合计算结果

通过Aggregations取出聚合对象，然后按名称获取聚合。

Aggregations aggregations = searchResponse.getAggregations();
Terms byCompanyAggregation = aggregations.get("by_company"); 
Bucket elasticBucket = byCompanyAggregation.getBucketByKey("Elastic"); 
Avg averageAge = elasticBucket.getAggregations().get("average_age"); 
double avg = averageAge.getValue();