ElasticSearch7.0 Java High Level Client使用教程（二：Scroll滚动查询）

上一篇里演示了ES简单的条件查询，值得注意的是，因为ES的深分页问题，单次查询最多只能返回10000条数据，如果要查询超过1万条数据，那就要用到Scroll滚动查询

代码

import com.alibaba.fastjson.JSONObject;
import org.apache.http.HttpHost;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.action.search.SearchScrollRequest;
import org.elasticsearch.action.search.SearchScrollRequestBuilder;
import org.elasticsearch.client.*;
import org.elasticsearch.common.unit.TimeValue;
import org.elasticsearch.index.query.BoolQueryBuilder;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.Scroll;
import org.elasticsearch.search.SearchHits;
import org.elasticsearch.search.aggregations.bucket.histogram.DateHistogramAggregationBuilder;
import org.elasticsearch.common.document.DocumentField;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.builder.SearchSourceBuilder;
import org.joda.time.DateTime;

import java.io.*;
import java.text.NumberFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.concurrent.TimeUnit;

public class ESReadTest {

	// ES的用户名，密码，地址
    private final String user = "user";
    private final String password = "password";
    private final String hostname = "127.0.0.1";
    private String indexName;
    private RestHighLevelClient client;

	// 用来将北京时间转换成UTC时间
    public String getUTCStr(String date) {
        String returnDate = "";
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        try {
            returnDate = new DateTime(sdf.parse(date)).plusHours(-8).toString("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
        }
        catch (ParseException e)
        {
            e.printStackTrace();
        }
        return returnDate;
    }

	// 初始化Client
    public void iniES(String indexName){
        final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY,
                new UsernamePasswordCredentials(user, password));

        RestClientBuilder builder = RestClient.builder(
                new HttpHost(hostname, 9200))
                .setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
                    public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
                        return httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);}});
        this.client = new RestHighLevelClient(builder);
        this.indexName=indexName;
    }

	//构建请求
    public List<String> dslBulider() throws IOException {
        SearchRequest searchRequest = new SearchRequest(this.indexName);
        SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
        // hit 返回值(bool 查询返回条数)
        searchSourceBuilder.size(3000);
//        searchSourceBuilder.from(0);
		// 准确计数
        searchSourceBuilder.trackTotalHits(true);
		// 超时时间60s
        searchSourceBuilder.timeout(new TimeValue(60, TimeUnit.SECONDS));

		// 绑定查询条件
        BoolQueryBuilder boolQueryBuilder = QueryBuilders.boolQuery();
        // status字段为301或302
        boolQueryBuilder.must(QueryBuilders.termsQuery("status.keyword", new String[]{"301","302"}));
        // args字段包含786754748671257
        boolQueryBuilder.must(QueryBuilders.matchPhraseQuery("args","786754748671257"));
        // 时间大于等于2020-05-21 00:00:00，小于2020-05-22 00:00:00
        boolQueryBuilder.must(QueryBuilders.rangeQuery("@timestamp").gte(getUTCStr("2020-05-21 00:00:00")).lt(getUTCStr("2020-05-22 00:00:00")));

        // 绑定bool query
        searchSourceBuilder.query(boolQueryBuilder);
        searchRequest.source(searchSourceBuilder);
		// 开启scroll查询,设置scroll过期时间为1min
		searchRequest.scroll("1m");
        
		// 发起请求并接收响应
        SearchResponse searchResponse = this.client.search(searchRequest, RequestOptions.DEFAULT);
		
		// 初始化查询结果List
		List<String> jsonStringList=new ArrayList<>();
		// 获取第一页的查询结果
        SearchHit[] searchHits=searchResponse.getHits().getHits();
        for (SearchHit hit : searchHits) {
            jsonStringList.add(hit.getSourceAsString());
        }
		// 获取ScrollId
        String scrollId = searchResponse.getScrollId();
		// 返回结果不为空则滚动查询
        while (searchHits != null && searchHits.length > 0){
			// 初始化scroll查询
            SearchScrollRequest searchScrollRequest=new SearchScrollRequest(scrollId);
            searchScrollRequest.scroll("1m");
			// 发起请求并接收响应
            searchResponse=this.client.searchScroll(searchScrollRequest,RequestOptions.DEFAULT);
			// 更新ScrollId
            scrollId=searchResponse.getScrollId();
			// 更新查询结果
            searchHits=searchResponse.getHits().getHits();
			// 放入List
            for (SearchHit hit : searchHits) {
                jsonStringList.add(hit.getSourceAsString());
            }
        }
		
        return jsonStringList;
    }

	// 关闭Client
    public void closeES(){
        try {
            this.client.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }

	// 运行
    public void run(){
        try {
			// 初始化并传入index名
            this.iniES("test*");
			// 获取查询结果并打印
            List<String> jsonStringList = this.dslBulider();
            for (String json : jsonStringList) {
                System.out.println(json);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            this.closeES();
        }
    }

    public static void main(String[] args) {
        ESReadTest esReadTest=new ESReadTest();
        esReadTest.run();
    }
}

可以看到，实际上第一次查询返回3000条数据，同时返回一个Scroll Id，之后使用这个Scroll Id循环查询直到返回结果为空，这样就能获得所有查询结果