第三章 Spring Data ElasticSearch 使用

3.1 Spring Data ElasticSearch简介

3.1.1 什么是Spring Data

Spring Data是一个用于简化数据库访问，并支持云服务的开源框架。其主要目标是使得对数据的访问变得方便快捷，并支持map-reduce框架和云计算数据服务。 Spring Data可以极大的简化JPA的写法，可以在几乎不用写实现的情况下，实现对数据的访问和操作。除了CRUD外，还包括如分页、排序等一些常用的功能。

Spring Data的官网：http://projects.spring.io/spring-data/

Spring Data常用的功能模块如下：

3.1.2 什么是Spring Data ElasticSearch

Spring Data ElasticSearch 基于 spring data API 简化 elasticSearch操作，将原始操作elasticSearch的客户端API 进行封装 。Spring Data为Elasticsearch项目提供集成搜索引擎。Spring Data Elasticsearch POJO的关键功能区域为中心的模型与Elastichsearch交互文档和轻松地编写一个存储库数据访问层。

官方网站：http://projects.spring.io/spring-data-elasticsearch/

3.2 Spring Data ElasticSearch入门

1）导入Spring Data ElasticSearch坐标

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.itheima</groupId><artifactId>itheima_elasticsearch_demo3</artifactId><version>1.0-SNAPSHOT</version><dependencies><dependency><groupId>org.elasticsearch</groupId><artifactId>elasticsearch</artifactId><version>5.6.8</version></dependency><dependency><groupId>org.elasticsearch.client</groupId><artifactId>transport</artifactId><version>5.6.8</version></dependency><dependency><groupId>org.apache.logging.log4j</groupId><artifactId>log4j-to-slf4j</artifactId><version>2.9.1</version></dependency><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-api</artifactId><version>1.7.24</version></dependency><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-simple</artifactId><version>1.7.21</version></dependency><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.12</version></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId><version>2.8.1</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.8.1</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-annotations</artifactId><version>2.8.1</version></dependency><dependency><groupId>org.springframework.data</groupId><artifactId>spring-data-elasticsearch</artifactId><version>3.0.5.RELEASE</version><exclusions><exclusion><groupId>org.elasticsearch.plugin</groupId><artifactId>transport-netty4-client</artifactId></exclusion></exclusions></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-test</artifactId><version>5.0.4.RELEASE</version></dependency></dependencies></project>

2）创建applicationContext.xml配置文件，引入elasticsearch命名空间

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xmlns:elasticsearch="http://www.springframework.org/schema/data/elasticsearch"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/data/elasticsearchhttp://www.springframework.org/schema/data/elasticsearch/spring-elasticsearch-1.0.xsd"></beans>

6） 配置applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xmlns:elasticsearch="http://www.springframework.org/schema/data/elasticsearch"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/data/elasticsearchhttp://www.springframework.org/schema/data/elasticsearch/spring-elasticsearch-1.0.xsd"><!-- 扫描Dao包，自动创建实例 --><elasticsearch:repositories base-package="com.itheima.dao"/><!-- 扫描Service包，创建Service的实体 --><context:component-scan base-package="com.itheima.service"/><!-- 配置elasticSearch的连接 --><!-- 配置elasticSearch的连接 --><elasticsearch:transport-client id="client" cluster-nodes="localhost:9300" cluster-name="my-elasticsearch"/><!-- ElasticSearch模版对象 --><bean id="elasticsearchTemplate" class="org.springframework.data.elasticsearch.core.ElasticsearchTemplate"><constructor-arg name="client" ref="client"></constructor-arg></bean></beans>

管理索引库

创建一个Entity类，其实就是一个JavaBean(pojo)映射到一个Document上需要添加一个注解进行标注。

package com.itheima.es.entity;import org.springframework.data.annotation.Id;
import org.springframework.data.elasticsearch.annotations.Document;
import org.springframework.data.elasticsearch.annotations.Field;
import org.springframework.data.elasticsearch.annotations.FieldType;@Document(indexName = "sdes_blog",type = "article") //映射一个文档上
public class Article {@Id@Field(type = FieldType.Long, store = true)private long id;@Field(type = FieldType.text, store = true,analyzer = "ik_smart")private String title;@Field(type = FieldType.text, store = true,analyzer = "ik_smart")private String content;public long getId() {return id;}public void setId(long id) {this.id = id;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getContent() {return content;}public void setContent(String content) {this.content = content;}
}

创建一个Dao,是一个接口，需要继承ElasticsearchRepository接口

package com.itheima.es.repositories;import com.itheima.es.entity.Article;
import org.springframework.data.elasticsearch.repository.ElasticsearchRepository;public interface ArticleRepository extends ElasticsearchRepository<Article,Long> {}

import com.itheima.es.entity.Article;
import com.itheima.es.repositories.ArticleRepository;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.elasticsearch.core.ElasticsearchTemplate;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext.xml")
public class SpringDataElasticSearchTest {@Autowiredprivate ArticleRepository articleRepository;@Autowiredprivate ElasticsearchTemplate template;@Testpublic void createIndex() throws Exception {///创建索引，并配置映射关系template.createIndex(Article.class);//配置映射关系//template.putMapping(Article.class);}}

3.3 Spring Data ElasticSearch的常用操作

3.3.1 增删改查方法测试

package com.itheima.service;import com.itheima.domain.Article;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;public interface ArticleService {//保存public void save(Article article);//删除public void delete(Article article);//查询全部public Iterable<Article> findAll();//分页查询public Page<Article> findAll(Pageable pageable);}

添加文档

   @Testpublic void addDocument() throws Exception{//创建一个Article对象Article article = new Article();article.setId(1);article.setTitle("Maven项目对象模型");article.setContent("Maven是一个采用Java编写的开元项目管理工具.");///把文档写入索引库articleRepository.save(article);}

删除文档

 @Testpublic void deleteDocumentById() throws Exception{articleRepository.deleteById(1l);//全部删除//articleRepository.deleteAll();}

简单查询文档

@Testpublic void findAll() throws Exception{Iterable<Article> all = articleRepository.findAll();all.forEach(a-> System.out.println(a));}

@Testpublic void testFindById() throws Exception{Optional<Article> byId = articleRepository.findById(1l);Article article = byId.get();System.out.println(article);}

自定义查询方法查询

package com.itheima.es.repositories;import com.itheima.es.entity.Article;
import org.springframework.data.domain.Pageable;
import org.springframework.data.elasticsearch.repository.ElasticsearchRepository;import java.util.List;public interface ArticleRepository extends ElasticsearchRepository<Article,Long> {List<Article> findByTitle(String title);List<Article> findByTitleOrContent(String title, String content);List<Article> findByTitleOrContent(String title, String content, Pageable pageable);
}

@Testpublic void testFindByTitle() throws Exception{List<Article> maven = articleRepository.findByTitle("maven");maven.stream().forEach(a -> System.out.println(a));}@Testpublic void testFindByTitleOrContent() throws Exception{articleRepository.findByTitleOrContent("maven", "商务与投资").forEach(a -> System.out.println(a));}@Testpublic void testFindByTitleOrContent1() throws Exception{PageRequest pageRequest = PageRequest.of(1, 5);articleRepository.findByTitleOrContent("maven", "商务与投资",pageRequest).forEach(a -> System.out.println(a));}

3.3.2 常用查询命名规则

3.3.3 查询方法测试

1）dao层实现

package com.itheima.dao;import com.itheima.domain.Article;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.elasticsearch.repository.ElasticsearchRepository;
import java.util.List;public interface ArticleRepository extends ElasticsearchRepository<Article, Integer> {//根据标题查询List<Article> findByTitle(String condition);//根据标题查询(含分页)Page<Article> findByTitle(String condition, Pageable pageable);
}

2）service层实现

public interface ArticleService {//根据标题查询List<Article> findByTitle(String condition);//根据标题查询(含分页)Page<Article> findByTitle(String condition, Pageable pageable);
}

package com.itheima.service.impl;import com.itheima.dao.ArticleRepository;
import com.itheima.domain.Article;
import com.itheima.service.ArticleService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.stereotype.Service;import java.util.List;@Service
public class ArticleServiceImpl implements ArticleService {@Autowiredprivate ArticleRepository articleRepository;public List<Article> findByTitle(String condition) {return articleRepository.findByTitle(condition);}public Page<Article> findByTitle(String condition, Pageable pageable) {return articleRepository.findByTitle(condition,pageable);}}

3）测试代码

package com.itheima.test;import com.itheima.domain.Article;
import com.itheima.service.ArticleService;
import org.elasticsearch.client.transport.TransportClient;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.elasticsearch.core.ElasticsearchTemplate;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;import java.util.List;@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations="classpath:applicationContext.xml")
public class SpringDataESTest {@Autowiredprivate ArticleService articleService;@Autowiredprivate TransportClient client;@Autowiredprivate ElasticsearchTemplate elasticsearchTemplate;/条件查询*/@Testpublic void findByTitle(){String condition = "版本";List<Article> articleList = articleService.findByTitle(condition);for(Article article:articleList){System.out.println(article);}}/条件分页查询*/@Testpublic void findByTitlePage(){String condition = "版本";Pageable pageable = PageRequest.of(2,10);Page<Article> page = articleService.findByTitle(condition,pageable);for(Article article:page.getContent()){System.out.println(article);}}}

3.3 Spring Data ElasticSearch的常用操作

3.3.1 增删改查方法测试

package com.itheima.service;import com.itheima.domain.Article;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;public interface ArticleService {//保存public void save(Article article);//删除public void delete(Article article);//查询全部public Iterable<Article> findAll();//分页查询public Page<Article> findAll(Pageable pageable);}

package com.itheima.service.impl;import com.itheima.dao.ArticleRepository;
import com.itheima.domain.Article;
import com.itheima.service.ArticleService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.stereotype.Service;@Service
public class ArticleServiceImpl implements ArticleService {@Autowiredprivate ArticleRepository articleRepository;public void save(Article article) {articleRepository.save(article);}public void delete(Article article) {articleRepository.delete(article);}public Iterable<Article> findAll() {Iterable<Article> iter = articleRepository.findAll();return iter;}public Page<Article> findAll(Pageable pageable) {return articleRepository.findAll(pageable);}
}

package com.itheima.test;import com.itheima.domain.Article;
import com.itheima.service.ArticleService;
import org.elasticsearch.client.transport.TransportClient;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.elasticsearch.core.ElasticsearchTemplate;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations="classpath:applicationContext.xml")
public class SpringDataESTest {@Autowiredprivate ArticleService articleService;@Autowiredprivate TransportClient client;@Autowiredprivate ElasticsearchTemplate elasticsearchTemplate;/创建索引和映射*/@Testpublic void createIndex(){elasticsearchTemplate.createIndex(Article.class);elasticsearchTemplate.putMapping(Article.class);}/测试保存文档*/@Testpublic void saveArticle(){Article article = new Article();article.setId(100);article.setTitle("测试SpringData ElasticSearch");article.setContent("Spring Data ElasticSearch 基于 spring data API 简化 elasticSearch操作，将原始操作elasticSearch的客户端API 进行封装 \\n" +"    Spring Data为Elasticsearch Elasticsearch项目提供集成搜索引擎");articleService.save(article);}/测试保存*/@Testpublic void save(){Article article = new Article();article.setId(1001);article.setTitle("elasticSearch 3.0版本发布");article.setContent("ElasticSearch是一个基于Lucene的搜索服务器。它提供了一个分布式多用户能力的全文搜索引擎，基于RESTful web接口");articleService.save(article);}/测试更新*/@Testpublic void update(){Article article = new Article();article.setId(1001);article.setTitle("elasticSearch 3.0版本发布...更新");article.setContent("ElasticSearch是一个基于Lucene的搜索服务器。它提供了一个分布式多用户能力的全文搜索引擎，基于RESTful web接口");articleService.save(article);}/测试删除*/@Testpublic void delete(){Article article = new Article();article.setId(1001);articleService.delete(article);}/批量插入*/@Testpublic void save100(){for(int i=1;i<=100;i++){Article article = new Article();article.setId(i);article.setTitle(i+"elasticSearch 3.0版本发布..，更新");article.setContent(i+"ElasticSearch是一个基于Lucene的搜索服务器。它提供了一个分布式多用户能力的全文搜索引擎，基于RESTful web接口");articleService.save(article);}}/分页查询*/@Testpublic void findAllPage(){Pageable pageable = PageRequest.of(1,10);Page<Article> page = articleService.findAll(pageable);for(Article article:page.getContent()){System.out.println(article);}}
}

3.3.4使用Elasticsearch的原生查询对象进行查询。

@Testpublic void findByNativeQuery() {//创建一个SearchQuery对象SearchQuery searchQuery = new NativeSearchQueryBuilder()//设置查询条件，此处可以使用QueryBuilders创建多种查询.withQuery(QueryBuilders.queryStringQuery("备份节点上没有数据").defaultField("title"))//还可以设置分页信息.withPageable(PageRequest.of(1, 5))//创建SearchQuery对象.build();//使用模板对象执行查询elasticsearchTemplate.queryForList(searchQuery, Article.class).forEach(a-> System.out.println(a));}

一、使用Java客户端管理ES
1、创建索引库
步骤：1）创建一个Java工程2）添加jar包，添加maven的坐标3）编写测试方法实现创建索引库1、创建一个Settings对象，相当于是一个配置信息。主要配置集群的名称。2、创建一个客户端Client对象3、使用client对象创建一个索引库4、关闭client对象
2、使用Java客户端设置Mappings步骤：1）创建一个Settings对象2）创建一个Client对象3）创建一个mapping信息，应该是一个json数据，可以是字符串，也可以是XContextBuilder对象4）使用client向es服务器发送mapping信息5）关闭client对象
3、添加文档步骤：1）创建一个Settings对象2）创建一个Client对象3）创建一个文档对象，创建一个json格式的字符串，或者使用XContentBuilder4）使用Client对象吧文档添加到索引库中5）关闭client
4、添加文档第二种方式创建一个pojo类使用工具类把pojo转换成json字符串把文档写入索引库二、使用es客户端实现搜索
1、根据id搜索QueryBuilder queryBuilder = QueryBuilders.idsQuery().addIds("1", "2");
2、根据Term查询（关键词）QueryBuilder queryBuilder = QueryBuilders.termQuery("title", "北方");
3、QueryString查询方式（带分析的查询）QueryBuilder queryBuilder = QueryBuilders.queryStringQuery("速度与激情").defaultField("title");
查询步骤：1）创建一个Client对象2）创建一个查询对象，可以使用QueryBuilders工具类创建QueryBuilder对象。3）使用client执行查询4）得到查询的结果。5）取查询结果的总记录数6）取查询结果列表7）关闭client
4、分页的处理在client对象执行查询之前，设置分页信息。然后再执行查询//执行查询SearchResponse searchResponse = client.prepareSearch("index_hello").setTypes("article").setQuery(queryBuilder)//设置分页信息.setFrom(0)//每页显示的行数.setSize(5).get();分页需要设置两个值，一个from、sizefrom：起始的行号，从0开始。size：每页显示的记录数
5、查询结果高亮显示
（1）高亮的配置1）设置高亮显示的字段2）设置高亮显示的前缀3）设置高亮显示的后缀
（2）在client对象执行查询之前，设置高亮显示的信息。
（3）遍历结果列表时可以从结果中取高亮结果。
三、SpringDataElasticSearch
1、工程搭建1）创建一个java工程。2）把相关jar包添加到工程中。如果maven工程就添加坐标。3）创建一个spring的配置文件1、配置elasticsearch:transport-client2、elasticsearch:repositories：包扫描器，扫描dao3、配置elasticsearchTemplate对象，就是一个bean
2、管理索引库1、创建一个Entity类，其实就是一个JavaBean（pojo）映射到一个Document上需要添加一些注解进行标注。2、创建一个Dao，是一个接口，需要继承ElasticSearchRepository接口。3、编写测试代码。3、创建索引直接使用ElasticsearchTemplate对象的createIndex方法创建索引，并配置映射关系。
4、添加、更新文档1）创建一个Article对象2）使用ArticleRepository对象向索引库中添加文档。
5、删除文档直接使用ArticleRepository对象的deleteById方法直接删除。
6、查询索引库直接使用ArticleRepository对象的查询方法。
7、自定义查询方法需要根据SpringDataES的命名规则来命名。如果不设置分页信息，默认带分页，每页显示10条数据。如果设置分页信息，应该在方法中添加一个参数PageablePageable pageable = PageRequest.of(0, 15);注意：设置分页信息，默认是从0页开始。可以对搜索的内容先分词然后再进行查询。每个词之间都是and的关系。
8、使用原生的查询条件查询NativeSearchQuery对象。使用方法：1）创建一个NativeSearchQuery对象设置查询条件，QueryBuilder对象2）使用ElasticSearchTemplate对象执行查询3）取查询结果

Article

package com.itheima.es.entity;import org.springframework.data.annotation.Id;
import org.springframework.data.elasticsearch.annotations.Document;
import org.springframework.data.elasticsearch.annotations.Field;
import org.springframework.data.elasticsearch.annotations.FieldType;@Document(indexName = "sdes_blog",type = "article") //映射一个文档上
public class Article {@Id@Field(type = FieldType.Long, store = true)private long id;@Field(type = FieldType.text, store = true,analyzer = "ik_smart")private String title;@Field(type = FieldType.text, store = true,analyzer = "ik_smart")private String content;public long getId() {return id;}public void setId(long id) {this.id = id;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getContent() {return content;}public void setContent(String content) {this.content = content;}@Overridepublic String toString() {return "Article{" +"id=" + id +", title='" + title + '\\'' +", content='" + content + '\\'' +'}';}
}

ArticleRepository

package com.itheima.es.repositories;import com.itheima.es.entity.Article;
import org.springframework.data.domain.Pageable;
import org.springframework.data.elasticsearch.repository.ElasticsearchRepository;import java.util.List;public interface ArticleRepository extends ElasticsearchRepository<Article,Long> {List<Article> findByTitle(String title);List<Article> findByTitleOrContent(String title, String content);List<Article> findByTitleOrContent(String title, String content, Pageable pageable);
}

测试

import com.itheima.es.entity.Article;
import com.itheima.es.repositories.ArticleRepository;
import org.elasticsearch.index.query.QueryBuilders;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.elasticsearch.core.ElasticsearchTemplate;
import org.springframework.data.elasticsearch.core.query.NativeSearchQuery;
import org.springframework.data.elasticsearch.core.query.NativeSearchQueryBuilder;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;import java.util.List;
import java.util.Optional;@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext.xml")
public class SpringDataElasticSearchTest {@Autowiredprivate ArticleRepository articleRepository;@Autowiredprivate ElasticsearchTemplate template;@Testpublic void createIndex() throws Exception {///创建索引，并配置映射关系template.createIndex(Article.class);//配置映射关系//template.putMapping(Article.class);}@Testpublic void addDocument() throws Exception{for (int i = 10; i < 20; i++) {//创建一个Article对象Article article = new Article();article.setId(i);article.setTitle("Maven项目对象模型2"+i);article.setContent("Maven是一个采用Java编写的开元项目管理工具2."+i);///把文档写入索引库articleRepository.save(article);}}@Testpublic void deleteDocumentById() throws Exception{articleRepository.deleteById(2l);//全部删除//articleRepository.deleteAll();}@Testpublic void findAll() throws Exception{Iterable<Article> all = articleRepository.findAll();all.forEach(a-> System.out.println(a));}@Testpublic void testFindById() throws Exception{Optional<Article> byId = articleRepository.findById(1l);Article article = byId.get();System.out.println(article);}@Testpublic void testFindByTitle() throws Exception{List<Article> maven = articleRepository.findByTitle("maven");maven.stream().forEach(a -> System.out.println(a));}@Testpublic void testFindByTitleOrContent() throws Exception{articleRepository.findByTitleOrContent("maven", "商务与投资").forEach(a -> System.out.println(a));}@Testpublic void testFindByTitleOrContent1() throws Exception{PageRequest pageRequest = PageRequest.of(1, 5);articleRepository.findByTitleOrContent("maven", "商务与投资",pageRequest).forEach(a -> System.out.println(a));}@Testpublic void testNativeSearchQuery() throws Exception{//创建一个查询对象NativeSearchQuery query = new NativeSearchQueryBuilder().withQuery(QueryBuilders.queryStringQuery("maven是一个工程构建工具").defaultField("title")).withPageable(PageRequest.of(1, 5)).build();//执行查询List<Article> articles = template.queryForList(query, Article.class);articles.forEach(article -> System.out.println(article));}
}