springboot elasticsearchresthighlevelclient 连接es

Java客户端分为低级客户端和高级客户端两种。低级客户端兼容所有版本的ES，但其需要提供JSON字符串，因此这种开发方式比较低效。高级客户端是基于低级客户端开发出来的，屏蔽了底层技术，使用户可以更专注于搜索业务，这是官方推荐的开发方式。本节介绍的Java客户端使用的是高级客户端。

演示RestHighLevelClient的使用，需要创建一个Spring Boot Web项目。该项目的依赖配置如下：

 elasticsearch 7.10.2

<!--ES客户端依赖-->
<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.10.2</version>
    <exclusions>
        <exclusion>
            <artifactId>elasticsearch-rest-client</artifactId>
            <groupId>org.elasticsearch.client</groupId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-client</artifactId>
    <version>7.10.2</version>
</dependency>
<!--ES依赖-->
<dependency>
    <groupId>org.elasticsearch</groupId>
    <artifactId>elasticsearch</artifactId>
    <version>7.10.2</version>
</dependency>

在application.yml文件中配置ES的连接信息如下：

spring:
  elasticsearch:
    rest:
      uris: 127.0.0.1:9200
      username: elasticsearch
      password:

Java客户端搜索文档

@Data
public class Hotel {

    String id;//对应于文档_id
    String index;//对应于索引名称
    Float score;//对应于文档得分

    String title; //对应于索引中的title
    String city; //对应于索引中的city
    Double price; //对应于索引中的price

}

@Service
public class EsService {

    @Autowired
    RestHighLevelClient restHighLevelClient;

    public List<Hotel> getHotelFromTitle(String keyword) {
        SearchRequest searchRequest = new SearchRequest("hotel");//客户端请求
        SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
        searchSourceBuilder.query(QueryBuilders.matchQuery("title", keyword));//构建query
        searchRequest.source(searchSourceBuilder);
        List<Hotel> resultList = new ArrayList<>();
        try {
            SearchResponse searchResponse = restHighLevelClient.search(searchRequest, RequestOptions.DEFAULT);
            RestStatus status = searchResponse.status();
            if (status != RestStatus.OK) {
                return null;
            }
            SearchHits searchHits = searchResponse.getHits();
            for (SearchHit searchHit : searchHits) {
                Hotel hotel = new Hotel();
                hotel.setId(searchHit.getId());//文档_id
                hotel.setIndex(searchHit.getIndex());//索引名称
                hotel.setScore(searchHit.getScore());//文档得分

                Map<String, Object> dataMap = searchHit.getSourceAsMap();//转换为Map
                hotel.setTitle((String) dataMap.get("title"));//设置标题
                hotel.setCity((String) dataMap.get("city"));//设置城市
                hotel.setPrice((Double) dataMap.get("price"));//设置价格
                resultList.add(hotel);
            }
            return resultList;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

}

@Slf4j
@Api(tags = "EsHotelController")
@RequestMapping("/es/hotel")
@RestController
public class EsHotelController {

    @Autowired
    EsService esService;

    @GetMapping(value = "/getHotelFromTitle")
    public String getHotelFromTitle(String title) {
        if (StringUtils.isEmpty(title)) {
            title = "再来";
        }

        List<Hotel> hotelList = esService.getHotelFromTitle(title);//调用Service完成搜索
        if (hotelList != null && hotelList.size() > 0) {//搜索到结果打印到前端
            return hotelList.toString();
        } else {
            return "no data.";
        }
    }

}

文章参考:Elasticsearch搜索引擎构建入门与实战 --> 2.2.1　Java客户端的使用