使用elasticsearch查询客户端java API获取字符串字段的不同值

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.15.1</version>
</dependency>

RestHighLevelClient client = new RestHighLevelClient(
        RestClient.builder(new HttpHost("localhost", 9200, "http")));

SearchRequest searchRequest = new SearchRequest("index_name");
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
TermsAggregationBuilder aggregationBuilder = AggregationBuilders.terms("unique_values").field("string_field");
searchSourceBuilder.aggregation(aggregationBuilder);
searchRequest.source(searchSourceBuilder);

SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);

Terms terms = searchResponse.getAggregations().get("unique_values");
List<? extends Terms.Bucket> buckets = terms.getBuckets();
for (Terms.Bucket bucket : buckets) {
    String uniqueValue = bucket.getKeyAsString();
    System.out.println(uniqueValue);
}