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;

     @Autowired
     private IHotelService hotelService;

     @Test
     void init(){
          System.out.println(client);
     }

     @BeforeEach
     void 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")
          ));
     }

     @AfterEach
     void tearDown() throws IOException {
          this.client.close();
     }


     @Test
     void testMatchAll() throws IOException {
          //准备Request
          SearchRequest 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;

     @Autowired
     private IHotelService hotelService;

     @Test
     void init(){
          System.out.println(client);
     }

     @BeforeEach
     void 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")
          ));
     }

     @AfterEach
     void tearDown() throws IOException {
          this.client.close();
     }


     @Test
     void testMatchAll() throws IOException {
          //准备Request
          SearchRequest 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

 @Test
     void testMatch() throws IOException {
          //准备Request
          SearchRequest 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

  @Test
     void testMatch() throws IOException {
          //准备Request
          SearchRequest 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

 @Test
     void testBool() throws IOException {
          //准备Request
          SearchRequest 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

 @Test
     void testPageAndSort() throws IOException {
          int pageNum = 1;
          int pageSize = 5;
          //准备Request
          SearchRequest 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

  @Test
     void testHighLight() throws IOException {
          //准备Request
          SearchRequest 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);
          }

     }