针对过滤聚合、嵌套聚合和词项聚合的新Elasticsearch客户端代码

以下是针对过滤聚合、嵌套聚合和词项聚合的Elasticsearch客户端代码示例：

import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.Client;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.aggregations.AggregationBuilders;
import org.elasticsearch.search.aggregations.bucket.filter.FilterAggregationBuilder;
import org.elasticsearch.search.aggregations.bucket.nested.NestedAggregationBuilder;
import org.elasticsearch.search.aggregations.bucket.terms.TermsAggregationBuilder;

public class ElasticsearchClient {

    private static final String INDEX_NAME = "my_index";
    private static final String FILTER_FIELD = "category";
    private static final String NESTED_FIELD = "comments";
    private static final String TERM_FIELD = "username";

    private Client client;

    public ElasticsearchClient() {
        this.client = createClient();
    }

    private Client createClient() {
        // Create Elasticsearch client
    }

    public SearchResponse search() {
        FilterAggregationBuilder filterAggregation = AggregationBuilders.filter("my_filter", QueryBuilders.termQuery(FILTER_FIELD, "books"));
        NestedAggregationBuilder nestedAggregation = AggregationBuilders.nested("my_nested", NESTED_FIELD);
        TermsAggregationBuilder termsAggregation = AggregationBuilders.terms("my_terms").field(TERM_FIELD);

        nestedAggregation.subAggregation(termsAggregation);
        filterAggregation.subAggregation(nestedAggregation);

        // Execute search request with aggregations
        return client.prepareSearch(INDEX_NAME)
                .setQuery(QueryBuilders.matchAllQuery())
                .addAggregation(filterAggregation)
                .execute()
                .actionGet();
    }
}