Elasticsearch Java HighLevel REST Client（Search API）

 Elasticsearch7.4 使用 RestHighLevelClient 簡單教程

第一步：引入maven jar包      

 <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.60</version>
   </dependency>
 <dependency>

    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.4.0</version>
    <!--可註釋，有詳細日誌打印-->
    <exclusions>
        <exclusion>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
        </exclusion>
        <exclusion>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>elasticsearch-rest-client</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-client</artifactId>
    <version>7.4.0</version>
</dependency>
<dependency>
    <groupId>org.elasticsearch</groupId>
    <artifactId>elasticsearch</artifactId>
    <version>7.4.0</version>
</dependency>

測試代碼：

import com.alibaba.fastjson.JSON;
import org.apache.http.HttpHost;
import org.elasticsearch.action.get.GetRequest;
import org.elasticsearch.action.get.GetResponse;
import org.elasticsearch.action.search.ClearScrollRequest;
import org.elasticsearch.action.search.ClearScrollResponse;
import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.action.search.SearchScrollRequest;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.core.CountRequest;
import org.elasticsearch.client.core.CountResponse;
import org.elasticsearch.client.indices.GetIndexRequest;
import org.elasticsearch.common.unit.TimeValue;
import org.elasticsearch.index.query.BoolQueryBuilder;
import org.elasticsearch.index.query.MatchAllQueryBuilder;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.Scroll;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchHits;
import org.elasticsearch.search.builder.SearchSourceBuilder;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

/**
 * @description:
 * @author: z
 * @createDate: 2020/3/2 1:19 PM
 * @Version: 1.0
 */
public class EsTest {
    private static String hosts = "10.201.233.225"; // 集羣地址，多個用,隔開
    private static int port = 9200; // 使用的端口號
    private static String schema = "http"; // 使用的協議

    public  static List<HttpHost> getHostList(){
        List<HttpHost> hostList = new ArrayList<>();
        String[] hostStrs = hosts.split(",");
        for (String host : hostStrs) {
            hostList.add(new HttpHost(host, port, schema));
        }
        return hostList;
    }

    public static RestHighLevelClient getClient(){

       RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(getHostList().toArray(new HttpHost[0])));
        return client;
    }

    public static void main(String[] args) throws InterruptedException, IOException {
        try(RestHighLevelClient client = getClient()) {
            //判斷 是否存在 索引
           // boolean exists = client.indices().exists(new GetIndexRequest("student"), RequestOptions.DEFAULT);
          //  System.out.println(exists);

           // GetRequest request = new GetRequest("student","1000");
           // GetResponse response = client.get(request, RequestOptions.DEFAULT);
             //System.out.println("getById:"+response.getSource());

            //Student 屬性 id，name，gender 等
            //Student user = JSON.parseObject(new String(response.getSourceAsBytes()), Student.class);
            //System.out.println(user.getId());

            SearchRequest searchRequest = new SearchRequest("student");

            // 這個可以理解  (name = '張三' or name = '李四') and gender='man'
            BoolQueryBuilder boolQueryBuilder = QueryBuilders.boolQuery()
                   // .must(QueryBuilders.termQuery("id", "10000")) id =10000
                    // matchQuery 聯想模糊，類似百度搜索框，matchPhraseQuery 類似與sql like 模糊查詢
                    .must(QueryBuilders.boolQuery().should(QueryBuilders.matchPhraseQuery("name", "張三"))
                            .should(QueryBuilders.matchPhraseQuery("name", "李四")))
                    .must(QueryBuilders.matchPhraseQuery("gender", "man"))
                    ;
            //  searchSourceBuilder.fetchSource(new String[]{"id","ts"}, null);//查詢字段
            // searchSourceBuilder.size(2);//返回記錄數
            searchRequest.source(new SearchSourceBuilder().query(boolQueryBuilder));

            SearchResponse searchResponse =  client.search(searchRequest, RequestOptions.DEFAULT);
            SearchHits hits = searchResponse.getHits();
            System.out.println("total:"+hits.getTotalHits());

            SearchHit[] searchHits = hits.getHits();
            System.out.println("size:"+searchHits.length);

            for(SearchHit hit : searchHits) {
                System.out.println("json data:"+hit.getSourceAsString());
                System.out.println("id:"+hit.getSourceAsMap().get("ts").toString());
               // System.out.println("---"+hit.getSourceAsString());
            }

            //滾動查詢
            scroll(client);

        }catch (Exception e){
            e.printStackTrace();
        }
    }

    /**
     * 獲取總記錄數
     * @param client
     * @return
     * @throws IOException
     */
    public static long getTotal(RestHighLevelClient client) throws IOException {
        SearchRequest searchRequest = new SearchRequest("student");
        MatchAllQueryBuilder matchAllQueryBuilder =  QueryBuilders.matchAllQuery();

        SearchSourceBuilder searchSourceBuilder =  new SearchSourceBuilder();
        searchSourceBuilder.query(matchAllQueryBuilder);
        searchRequest.source(searchSourceBuilder);

        CountRequest countRequest = new CountRequest("student");
        // System.out.println(countRequest.source().toString());
        CountResponse response = client.count(countRequest, RequestOptions.DEFAULT);
        System.out.println("total:"+response.getCount());
        //打印查詢語句字符串
        System.out.println(searchSourceBuilder.toString());
        return response.getCount();
    }

    /**
     * scroll 滾動查詢
     * @param client
     */
    public static void scroll(RestHighLevelClient client) throws IOException {
        //初始化scroll
        final Scroll scroll = new Scroll(TimeValue.timeValueMinutes(1L)); //設定滾動時間間隔
        SearchRequest searchRequest = new SearchRequest("student");
        searchRequest.scroll(scroll);

        SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
        //這裏查詢所有，可以  QueryBuilders.boolQuery() QueryBuilders 設置查詢條件，
        searchSourceBuilder.query(QueryBuilders.matchAllQuery());
        searchSourceBuilder.size(2); //設定每次返回多少條數據
        searchRequest.source(searchSourceBuilder);

        System.out.println(searchSourceBuilder.toString());
        SearchResponse searchResponse = null;
        searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
        
        String scrollId = searchResponse.getScrollId();
        System.out.println(searchResponse.getHits().getTotalHits());
        SearchHit[] searchHits = searchResponse.getHits().getHits();
        System.out.println("----第一頁-----》");
        for (SearchHit searchHit : searchHits) {
            System.out.println(searchHit.getSourceAsString());
        }
        //遍歷符合搜索條件的數據，直到沒有數據
        while (searchHits != null && searchHits.length > 0) {
            SearchScrollRequest scrollRequest = new SearchScrollRequest(scrollId);
            scrollRequest.scroll(scroll);

            searchResponse = client.scroll(scrollRequest, RequestOptions.DEFAULT);

            scrollId = searchResponse.getScrollId();
            searchHits = searchResponse.getHits().getHits();
            if (searchHits != null && searchHits.length > 0) {
                System.out.println("----下一頁-----》");
                for (SearchHit searchHit : searchHits) {
                    System.out.println(searchHit.getSourceAsString());
                }
            }

        }
        //清除滾屏
        ClearScrollRequest clearScrollRequest = new ClearScrollRequest();
        //或者用setScrollIds()指定多個scrollId 
        clearScrollRequest.addScrollId(scrollId);
        ClearScrollResponse clearScrollResponse = null;

        clearScrollResponse = client.clearScroll(clearScrollRequest,RequestOptions.DEFAULT);
        boolean succeeded = clearScrollResponse.isSucceeded();
        System.out.println("succeeded:" + succeeded);
    }

}

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