实用篇-ES-RestClient查询文档

一、快速入门

上面的查询文档都是依赖kibana，在浏览器页面使用DSL语句去查询es，如何用java去查询es里面的文档(数据)呢
我们通过match_all查询来演示基本的API，注意下面演示的是 'match_all查询，也叫基础查询'
首先保证你已经做好了 '实用篇-ES-环境搭建' ，创建了名为gghotel的索引库，然后开始下面的操作。如果需要浏览器操作es，那就不需要启动kibana容器

在进行下面的操作之前，确保你已经看了前面 '实用篇-ES-RestClient操作文档' 学的 '1. RestClient案例准备'，然后在进行下面的操作

第一步: 在src/test/java/cn.itcast.hotel目录新建HotelSearchTest类，写入如下

package cn.itcast.hotel;import cn.itcast.hotel.service.IHotelService;
import org.apache.http.HttpHost;
import org.elasticsearch.action.search.SearchRequest;
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.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.io.IOException;@SpringBootTest
public class HotelIndexTest2 {private RestHighLevelClient client;@Autowiredprivate IHotelService hotelService;@Testvoid init(){System.out.println(client);}@BeforeEachvoid setUp(){this.client = new RestHighLevelClient(RestClient.builder(//指定你Centos7部署的es的主机地址HttpHost.create("http://192.168.229.129:9200")));}@AfterEachvoid tearDown() throws IOException {this.client.close();}@Testvoid testMatchAll() throws IOException {//准备RequestSearchRequest request = new SearchRequest("hotel");//组织DSL参数request.source().query(QueryBuilders.matchAllQuery());//发送请求，得到响应结果SearchResponse response = client.search(request, RequestOptions.DEFAULT);System.out.println(response);}}

第二步: 把控制台里面我们需要的数据解析出来。返回的数据很多，我们主要是解析hits里面的数据就行了

把HotelSearchTest类修改为如下，主要的修改是sout之前做了一次解析，拿到我们想要的数据

package cn.itcast.hotel;import cn.itcast.hotel.pojo.HotelDoc;
import cn.itcast.hotel.service.IHotelService;
import com.alibaba.fastjson.JSON;
import org.apache.http.HttpHost;
import org.elasticsearch.action.search.SearchRequest;
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.SearchHit;
import org.elasticsearch.search.SearchHits;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.io.IOException;@SpringBootTest
public class HotelIndexTest2 {private RestHighLevelClient client;@Autowiredprivate IHotelService hotelService;@Testvoid init(){System.out.println(client);}@BeforeEachvoid setUp(){this.client = new RestHighLevelClient(RestClient.builder(//指定你Centos7部署的es的主机地址HttpHost.create("http://192.168.229.129:9200")));}@AfterEachvoid tearDown() throws IOException {this.client.close();}@Testvoid testMatchAll() throws IOException {//准备RequestSearchRequest request = new SearchRequest("hotel");//组织DSL参数request.source().query(QueryBuilders.matchAllQuery());//发送请求，得到响应结果SearchResponse response = client.search(request, RequestOptions.DEFAULT);//下面为逐层解析json数据SearchHits searchHits = response.getHits();long total = searchHits.getTotalHits().value;System.out.println("共有" + total + "条数据");SearchHit[] hits = searchHits.getHits();for (SearchHit hit : hits) {String json = hit.getSourceAsString();//反系列化HotelDoc hotelDoc = JSON.parseObject(json, HotelDoc.class);System.out.println("hotelDoc = " + hotelDoc);}}}

二、match的三种查询

我们刚刚在第一节演示的是 match_all(也叫基本查询) 查询，下面将演示 match(也叫单字段查询) 和 multi_match(也叫多字段查询) 查询

【match 查询，也叫单字段查询】

在HotelSearchTest类添加如下

 @Testvoid testMatch() throws IOException {//准备RequestSearchRequest request = new SearchRequest("hotel");//组织DSL参数request.source().query(QueryBuilders.matchQuery("name","如家"));//发送请求，得到响应结果SearchResponse response = client.search(request, RequestOptions.DEFAULT);//下面为逐层解析json数据SearchHits searchHits = response.getHits();long total = searchHits.getTotalHits().value;System.out.println("共有" + total + "条数据");SearchHit[] hits = searchHits.getHits();for (SearchHit hit : hits) {String json = hit.getSourceAsString();//反系列化HotelDoc hotelDoc = JSON.parseObject(json, HotelDoc.class);System.out.println("hotelDoc = " + hotelDoc);}}

【multi_match 查询，也叫多字段查询】

在HotelSearchTest类添加如下

  @Testvoid testMatch() throws IOException {//准备RequestSearchRequest request = new SearchRequest("hotel");//组织DSL参数request.source().query(QueryBuilders.multiMatchQuery("如家","name","business"));//发送请求，得到响应结果SearchResponse response = client.search(request, RequestOptions.DEFAULT);//下面为逐层解析json数据SearchHits searchHits = response.getHits();long total = searchHits.getTotalHits().value;System.out.println("共有" + total + "条数据");SearchHit[] hits = searchHits.getHits();for (SearchHit hit : hits) {String json = hit.getSourceAsString();//反系列化HotelDoc hotelDoc = JSON.parseObject(json, HotelDoc.class);System.out.println("hotelDoc = " + hotelDoc);}}

总结: 要构建查询条件，只要记住一个QueryBuilders类即可

三、解析代码的抽取

我们发现对于 match、multi_match、match_all 查询，的解析部分的代码都是相同的，所以我们可以对解析部分的代码进行抽取，如下

快捷键ctrl + alt + M

  private void handleResponse(SearchResponse response) {//下面为逐层解析json数据SearchHits searchHits = response.getHits();long total = searchHits.getTotalHits().value;System.out.println("共有" + total + "条数据");SearchHit[] hits = searchHits.getHits();for (SearchHit hit : hits) {String json = hit.getSourceAsString();//反系列化HotelDoc hotelDoc = JSON.parseObject(json, HotelDoc.class);System.out.println("hotelDoc = " + hotelDoc);}}

之后我们在test中只专注于json的获取，解析的任务交给这段代码

四、bool和term、rang精确查询

原理同上

我们直接演示bool复合查询

 @Testvoid testBool() throws IOException {//准备RequestSearchRequest request = new SearchRequest("hotel");//组织DSL参数BoolQueryBuilder boolQuery = QueryBuilders.boolQuery();boolQuery.must(QueryBuilders.termQuery("city","杭州"));boolQuery.filter(QueryBuilders.rangeQuery("price").lte(250));request.source().query(boolQuery);//发送请求，得到响应结果SearchResponse response = client.search(request, RequestOptions.DEFAULT);handleResponse(response);}

五、排序和分页

 @Testvoid testPageAndSort() throws IOException {int pageNum = 1;int pageSize = 5;//准备RequestSearchRequest request = new SearchRequest("hotel");//组织DSL参数//查询所有request.source().query(QueryBuilders.matchAllQuery());//排序request.source().sort("price", SortOrder.ASC);//分页request.source().from(pageNum - 1).size(pageSize);//发送请求，得到响应结果SearchResponse response = client.search(request, RequestOptions.DEFAULT);handleResponse(response);}

六、高亮显示

高亮API包括请求DSL构建和结果解析两部分，API和对应的DSL语句如下图，下图只是构建，再下面还有解析，高亮必须由构建+解析才能实现

解析，如下图

  @Testvoid testHighLight() throws IOException {//准备RequestSearchRequest request = new SearchRequest("hotel");//组织DSL参数//查询所有request.source().query(QueryBuilders.matchQuery("name","如家"));//设置高亮匹配方式request.source().highlighter(new HighlightBuilder().field("name").requireFieldMatch(false));//发送请求，得到响应结果SearchResponse response = client.search(request, RequestOptions.DEFAULT);//下面为逐层解析json数据SearchHits searchHits = response.getHits();long total = searchHits.getTotalHits().value;System.out.println("共有" + total + "条数据");SearchHit[] hits = searchHits.getHits();for (SearchHit hit : hits) {String json = hit.getSourceAsString();//反系列化HotelDoc hotelDoc = JSON.parseObject(json, HotelDoc.class);//解析，获取高亮结果Map<String, HighlightField> highlightFields = hit.getHighlightFields();if(!CollectionUtils.isEmpty(highlightFields)){//根据字段名获取高亮结果HighlightField highlightField = highlightFields.get("name");//判断高亮字段不为空if(highlightField!=null){//获取高亮值String name = highlightField.getFragments()[0].string();//覆盖非高亮结果hotelDoc.setName(name);}}//最终输出System.out.println("hotelDoc = " + hotelDoc);}}