ElasticSearch工具类

Elasticsearch是一个开源的分布式搜索和分析引擎，它被广泛应用于全文搜索、日志分析、数据可视化等领域。Elasticsearch提供了丰富的API和功能，可以方便地进行数据索引、搜索、聚合和分析。

在使用Elasticsearch时，可以使用Java编写工具类来简化与Elasticsearch的交互。下面是一个简单的Elasticsearch工具类的示例：

import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.builder.SearchSourceBuilder;
import org.elasticsearch.search.sort.SortOrder;

import java.io.IOException;

public class ElasticsearchUtils {
    private RestHighLevelClient client;

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

    public SearchResponse search(String index, String field, String keyword) throws IOException {
        SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
        sourceBuilder.query(QueryBuilders.matchQuery(field, keyword));
        sourceBuilder.sort(field, SortOrder.DESC);

        SearchRequest searchRequest = new SearchRequest(index);
        searchRequest.source(sourceBuilder);

        return client.search(searchRequest, RequestOptions.DEFAULT);
    }

    public void close() throws IOException {
        client.close();
    }
}

上述示例中的工具类使用了Elasticsearch的Java高级客户端（RestHighLevelClient）来与Elasticsearch进行交互。其中，`search`方法用于执行搜索操作，`close`方法用于关闭与Elasticsearch的连接。