ElasticSearch7.0 Java High Level Client使用教程（一：简单查询）

本文将演示如何使用ES提供的Java高级包来查询数据，首先API其实就是在底层构建一条DSL查询语句，所以我们首先看一下这条语句:

GET test*/_search
{
  "timeout": "60s",
  "query": {
    "bool": {
      "must": [
        {
          "terms": {
            "status.keyword": [
              "301",
              "302"
            ],
            "boost": 1
          }
        },
        {
          "match_phrase": {
            "args": {
              "query": "786754748671257",
              "slop": 0,
              "zero_terms_query": "NONE",
              "boost": 1
            }
          }
        },
        {
          "range": {
            "@timestamp": {
              "from": "2020-05-20T16:00:00.000Z",
              "to": "2020-05-21T16:00:00.000Z",
              "include_lower": true,
              "include_upper": false,
              "boost": 1
            }
          }
        }
      ],
      "adjust_pure_negative": true,
      "boost": 1
    }
  },
  "track_total_hits": 2147483647
}

接下来代码里的绑定查询条件部分都是围绕这条语句来写的

一 maven依赖

	<dependency>
            <groupId>org.apache.httpcomponentsgroupId>
            <artifactId>httpclientartifactId>
            <version>4.5.6version>
	dependency>
	<dependency>
            <groupId>org.elasticsearchgroupId>
            <artifactId>elasticsearchartifactId>
            <version>7.0.1version>
	dependency>
	<dependency>
            <groupId>org.elasticsearch.clientgroupId>
            <artifactId>elasticsearch-rest-high-level-clientartifactId>
            <version>7.0.1version>
	dependency>
	
	<dependency>
            <groupId>joda-timegroupId>
            <artifactId>joda-timeartifactId>
            <version>2.10.1version>
	dependency>

二 代码

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.client.*;
import org.elasticsearch.common.unit.TimeValue;
import org.elasticsearch.index.query.BoolQueryBuilder;
import org.elasticsearch.index.query.QueryBuilders;
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.IOException;
import java.text.NumberFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
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 SearchResponse 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(0);
//        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);
        // 打印dsl语句
        System.out.println("dsl is："+searchRequest.source());
		// 发起请求并接收响应
        SearchResponse searchResponse = this.client.search(searchRequest, RequestOptions.DEFAULT);
        return searchResponse;
    }

	// 解析响应
    public List<String> dslParse(SearchResponse searchResponse) {
        List<String> jsonStringList=new ArrayList<>();
        for (SearchHit hit : searchResponse.getHits().getHits()) {
            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.dslParse(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();
    }
}

程序运行后将以json格式打印出符合查询条件的数据

三

以上介绍了按条件简单查询的例子，下一篇里将会介绍如何绑定聚合条件进行聚合查询