552、Elasticsearch详细入门教程系列 -【分布式全文搜索引擎 Elasticsearch（三）】 2023.05.19

一、Elasticsearch——使用Java API实现ES中的索引、映射、文档操作

1.1 简单介绍

之前是对ES中的创建/查看/删除索引、创建定义映射、创建/查看/修改/删除文档的这些操作有了一定的了解认识，但是是通过Postman + JSON串的方法来实现的
那么之后仍然是对ES中的索引、映射、文档进行操作，只是方法换成了Java API。

1.2 案例详情

首先需要创建一个maven工程，必然要添加ES相关的依赖。
同时双击ES安装目录的bin目录下的 elasticsearch.bat ，先启动ES服务端。

• pom文件

       <dependency>
           <groupId>org.elasticsearch</groupId>
           <artifactId>elasticsearch</artifactId>
           <version>7.8.0</version>
       </dependency>
       <!-- elasticsearch 的客户端 -->
       <dependency>
           <groupId>org.elasticsearch.client</groupId>
           <artifactId>elasticsearch-rest-high-level-client</artifactId>
           <version>7.8.0</version>
       </dependency>
       <!-- elasticsearch 依赖 2.x 的 log4j -->
       <dependency>
           <groupId>org.apache.logging.log4j</groupId>
           <artifactId>log4j-api</artifactId>
           <version>2.8.2</version>
       </dependency>
       <dependency>
           <groupId>org.apache.logging.log4j</groupId>
           <artifactId>log4j-core</artifactId>
           <version>2.8.2</version>
       </dependency>
       <dependency>
           <groupId>com.fasterxml.jackson.core</groupId>
           <artifactId>jackson-databind</artifactId>
           <version>2.9.9</version>
       </dependency>
       <!-- junit 单元测试 -->
       <dependency>
           <groupId>junit</groupId>
           <artifactId>junit</artifactId>
           <version>4.12</version>
       </dependency>

1.2.1 创建ES客户端：完成与ES服务端连接

后边都是按照这个模板代码来的

package com.szh.es;

import org.apache.http.HttpHost;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;

import java.io.IOException;

/**
*
*/
public class ESTestClient {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //关闭ES客户端
       esClient.close();
   }
}

1.2.2 创建索引

//创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //创建索引 --- 请求对象
       CreateIndexRequest request = new CreateIndexRequest("user");
       //发送请求 --- 获取响应
       CreateIndexResponse response = esClient.indices().create(request, RequestOptions.DEFAULT);

       //响应状态
       boolean acknowledged = response.isAcknowledged();
       System.out.println("索引操作：" + acknowledged);

       //关闭ES客户端
       esClient.close();

1.2.3 查看索引

public class ESTestIndexSearch {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //查询索引 --- 请求对象
       GetIndexRequest request = new GetIndexRequest("user");
       //发送请求 --- 获取响应
       GetIndexResponse response = esClient.indices().get(request, RequestOptions.DEFAULT);

       //响应状态
       System.out.println(response.getAliases());
       System.out.println(response.getMappings());
       System.out.println(response.getSettings());

       //关闭ES客户端
       esClient.close();
   }
}

1.2.4 删除索引

public class ESTestIndexDelete {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //删除索引 --- 请求对象
       DeleteIndexRequest request = new DeleteIndexRequest("user");
       //发送请求 --- 获取响应
       AcknowledgedResponse response = esClient.indices().delete(request,RequestOptions.DEFAULT);

       //响应状态
       System.out.println(response.isAcknowledged());

       //关闭ES客户端
       esClient.close();
   }
}

1.2.5 创建文档

索引有了，就相当于有了数据库。接下来就需要向数据库中建表、添加数据。建表自然要有表结构（有哪些属性、这些属性分别都是什么数据类型），也就是ES中的映射，在Java代码中就可以采用实体类来实现。

public class User {

   private String name;
   private String sex;
   private Integer age;

   //getter and setter
}

public class ESTestDocInsert {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //创建文档 --- 请求对象
       IndexRequest request = new IndexRequest();
       //设置索引及索引中文档的唯一性标识id（如果不指定，则ES会默认随机生成一个id）
       request.index("user").id("1001");

       //创建数据对象（文档内容）
       User user = new User();
       user.setName("张起灵");
       user.setSex("man");
       user.setAge(21);

       //向ES中插入数据，必须将数据格式转换为JSON
       ObjectMapper objectMapper = new ObjectMapper();
       String userJson = objectMapper.writeValueAsString(user);
       request.source(userJson, XContentType.JSON);

       //发送请求 --- 获取响应
       IndexResponse response = esClient.index(request, RequestOptions.DEFAULT);
       System.out.println(response.getResult());

       //关闭ES客户端
       esClient.close();
   }
}

1.2.6 修改文档

public class ESTestDocUpdate {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //修改文档 --- 请求对象
       UpdateRequest request = new UpdateRequest();
       //配置修改参数 --- 表示要修改user索引中id为1001的文档内容
       request.index("user").id("1001");
       //将修改后的内容，以JSON格式写入请求体中
       request.doc(XContentType.JSON,"age",18);

       //发送请求 --- 获取响应
       UpdateResponse response = esClient.update(request,RequestOptions.DEFAULT);
       System.out.println(response.getResult());

       //关闭ES客户端
       esClient.close();
   }
}

1.2.7 查看文档

public class ESTestDocSearch {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //查询文档 --- 请求对象
       GetRequest request = new GetRequest();
       //设置请求参数 --- 表示要查询user索引中id为1001的文档内容
       request.index("user").id("1001");

       //发送请求 --- 获取响应
       GetResponse response = esClient.get(request,RequestOptions.DEFAULT);
       System.out.println(response.getSourceAsString());

       //关闭ES客户端
       esClient.close();
   }
}

1.2.8 删除文档

public class ESTestDocDelete {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //删除文档 --- 请求对象
       DeleteRequest request = new DeleteRequest();
       //设置请求参数 --- 表示要删除user索引中id为1001的文档
       request.index("user").id("1001");
       
       //发送请求 --- 获取响应
       DeleteResponse response = esClient.delete(request,RequestOptions.DEFAULT);
       System.out.println(response.getResult());

       //关闭ES客户端
       esClient.close();
   }
}

1.2.9 批量创建文档

public class ESTestDocInsertBatch {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //批量新增文档 --- 请求对象
       BulkRequest request = new BulkRequest();
       //以JSON格式批量新增文档 --- 存入请求体中
       request.add(new IndexRequest().index("user").id("1001").source(XContentType.JSON, "name", "张起灵","sex","boy","age",21));
       request.add(new IndexRequest().index("user").id("1002").source(XContentType.JSON, "name", "小哥","sex","boy","age",18));
       request.add(new IndexRequest().index("user").id("1003").source(XContentType.JSON, "name", "小宋","sex","boy","age",20));

       //发送请求 --- 获取响应
       BulkResponse response = esClient.bulk(request, RequestOptions.DEFAULT);
       System.out.println(response.getTook());

       //关闭ES客户端
       esClient.close();
   }
}

1.2.10 批量删除文档

public class ESTestDocDeleteBatch {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //批量删除文档 --- 请求对象
       BulkRequest request = new BulkRequest();
       //将要删除的文档id存入请求体中
       request.add(new DeleteRequest().index("user").id("1001"));
       request.add(new DeleteRequest().index("user").id("1002"));
       request.add(new DeleteRequest().index("user").id("1003"));

       //发送请求 --- 获取响应
       BulkResponse response = esClient.bulk(request,RequestOptions.DEFAULT);
       System.out.println(response.getTook());
       System.out.println(response.getItems());

       //关闭ES客户端
       esClient.close();
   }
}

1.2.11 全量查询

因为上面两个代码案例分别进行了批量创建、批量删除。所以这里首先执行一次批量创建的代码，确保索引中有多条数据供我们查询。

public class ESTestDocInsertBatch {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //批量新增文档 --- 请求对象
       BulkRequest request = new BulkRequest();
       //以JSON格式批量新增文档 --- 存入请求体中
       request.add(new IndexRequest().index("user").id("1001").source(XContentType.JSON, "name", "张起灵","sex","boy","age",21));
       request.add(new IndexRequest().index("user").id("1002").source(XContentType.JSON, "name", "小哥","sex","boy","age",18));
       request.add(new IndexRequest().index("user").id("1003").source(XContentType.JSON, "name", "小宋","sex","boy","age",20));
       request.add(new IndexRequest().index("user").id("1004").source(XContentType.JSON, "name", "冷少","sex","boy","age",25));
       request.add(new IndexRequest().index("user").id("1005").source(XContentType.JSON, "name", "Java软件工程师","sex","girl","age",40));

       //发送请求 --- 获取响应
       BulkResponse response = esClient.bulk(request, RequestOptions.DEFAULT);
       System.out.println(response.getTook());

       //关闭ES客户端
       esClient.close();
   }
}

下面首先进行全量查询操作。

public class ESTestDocQuery {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //1.查询索引中的全部文档 --- matchAllQuery 全量查询
       //创建搜索请求对象
       SearchRequest request = new SearchRequest();
       //设置参数 --- 表示查询哪个索引中的文档内容
       request.indices("user");
       //构建查询的请求体 --- 存入搜索请求对象中
       request.source(new SearchSourceBuilder().query(QueryBuilders.matchAllQuery()));

       //发送请求 --- 获取响应
       SearchResponse response = esClient.search(request,RequestOptions.DEFAULT);
       //获取查询到的结果集
       SearchHits hits = response.getHits();
       System.out.println(hits.getTotalHits()); //结果集的条数
       System.out.println(response.getTook());  //总耗时
       //遍历结果集
       for (SearchHit hit : hits) {
           System.out.println(hit.getSourceAsString());
       }

       //关闭ES客户端
       esClient.close();
   }
}

1.2.12 条件查询

做匹配查询，查询年龄age=21的文档内容。

public class ESTestDocQuery {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //2.条件查询--- termQuery age=21
       //创建搜索请求对象
       SearchRequest request = new SearchRequest();
       //设置参数 --- 表示查询哪个索引中的文档内容
       request.indices("user");
       //构建查询的请求体 --- 存入搜索请求对象中
       request.source(new SearchSourceBuilder().query(QueryBuilders.termQuery("age",21)));

       //发送请求 --- 获取响应
       SearchResponse response = esClient.search(request,RequestOptions.DEFAULT);
       //获取查询到的结果集
       SearchHits hits = response.getHits();
       System.out.println(hits.getTotalHits()); //结果集的条数
       System.out.println(response.getTook());  //总耗时
       //遍历结果集
       for (SearchHit hit : hits) {
           System.out.println(hit.getSourceAsString());
       }

       //关闭ES客户端
       esClient.close();
   }
}

1.2.13 分页查询

做全量查询，对查询结果进行分页显示，每页2条数据，查询第1页。
查看第几页：（页码 - 1）*每页条数

public class ESTestDocQuery {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //3.分页查询
       //创建搜索请求对象
       SearchRequest request = new SearchRequest();
       //设置参数 --- 表示查询哪个索引中的文档内容
       request.indices("user");
       //构建查询的请求体
       SearchSourceBuilder builder = new SearchSourceBuilder().query(QueryBuilders.matchAllQuery());
       builder.from(0);
       builder.size(2);
       //将构建好的查询请求体存入搜索请求对象中
       request.source(builder);

       //发送请求 --- 获取响应
       SearchResponse response = esClient.search(request,RequestOptions.DEFAULT);
       //获取查询到的结果集
       SearchHits hits = response.getHits();
       System.out.println(hits.getTotalHits()); //结果集的条数
       System.out.println(response.getTook());  //总耗时
       //遍历结果集
       for (SearchHit hit : hits) {
           System.out.println(hit.getSourceAsString());
       }

       //关闭ES客户端
       esClient.close();
   }
}

1.2.14 排序查询

做全量查询，对查询结果中的年龄age字段做降序排序。

public class ESTestDocQuery {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //4.对查询结果进行排序
       //创建搜索请求对象
       SearchRequest request = new SearchRequest();
       //设置参数 --- 表示查询哪个索引中的文档内容
       request.indices("user");
       //构建查询的请求体
       SearchSourceBuilder builder = new SearchSourceBuilder().query(QueryBuilders.matchAllQuery());
       builder.sort("age", SortOrder.DESC);
       //将构建好的查询请求体存入搜索请求对象中
       request.source(builder);

       //发送请求 --- 获取响应
       SearchResponse response = esClient.search(request,RequestOptions.DEFAULT);
       //获取查询到的结果集
       SearchHits hits = response.getHits();
       System.out.println(hits.getTotalHits()); //结果集的条数
       System.out.println(response.getTook());  //总耗时
       //遍历结果集
       for (SearchHit hit : hits) {
           System.out.println(hit.getSourceAsString());
       }

       //关闭ES客户端
       esClient.close();
   }
}

1.2.15 过滤字段查询

做全量查询，同时排除性别sex字段。

public class ESTestDocQuery {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //5.过滤字段
       //创建搜索请求对象
       SearchRequest request = new SearchRequest();
       //设置参数 --- 表示查询哪个索引中的文档内容
       request.indices("user");
       //构建查询的请求体
       SearchSourceBuilder builder = new SearchSourceBuilder().query(QueryBuilders.matchAllQuery());
       String[] excludes = {"sex"};
       String[] includes = {};
       builder.fetchSource(includes,excludes);
       //将构建好的查询请求体存入搜索请求对象中
       request.source(builder);

       //发送请求 --- 获取响应
       SearchResponse response = esClient.search(request,RequestOptions.DEFAULT);
       //获取查询到的结果集
       SearchHits hits = response.getHits();
       System.out.println(hits.getTotalHits()); //结果集的条数
       System.out.println(response.getTook());  //总耗时
       //遍历结果集
       for (SearchHit hit : hits) {
           System.out.println(hit.getSourceAsString());
       }

       //关闭ES客户端
       esClient.close();
   }
}

1.2.16 组合条件查询

查询年龄 age=18 或者 name=张起灵 的文档内容。

public class ESTestDocQuery {
   public static void main(String[] args) throws IOException {
       //创建ES客户端
       RestHighLevelClient esClient = new RestHighLevelClient(
               RestClient.builder(new HttpHost("localhost",9200,"http"))
       );

       //6.组合查询
       //创建搜索请求对象
       SearchRequest request = new SearchRequest();
       //设置参数 --- 表示查询哪个索引中的文档内容
       request.indices("user");
       //构建查询的请求体
       SearchSourceBuilder builder = new SearchSourceBuilder();
       BoolQueryBuilder boolQueryBuilder = QueryBuilders.boolQuery();
       boolQueryBuilder.should(QueryBuilders.matchQuery("age",18));
       boolQueryBuilder.should(QueryBuilders.matchQuery("name","张起灵"));
       builder.query(boolQueryBuilder);
       //将构建好的查询请求体存入搜索请求对象中
       request.source(builder);

       //发送请求 --- 获取响应
       SearchResponse response = esClient.search(request,RequestOptions.DEFAULT);
       //获取查询到的结果集
       SearchHits hits = response.getHits();
       System.out.println(hits.getTotalHits()); //结果集的条数
       System.out.println(response.getTook());  //总耗时
       //遍历结果集
       for (SearchHit hit : hits) {
           System.out.println(hit.getSourceAsString());
       }

       //关闭ES客户端
       esClient.close();
   }
}

 RestClient.builder(new HttpHost("localhost",9200,"http"))

二、参考链接

[01] 分布式全文搜索引擎 Elasticsearch文章来源地址https://www.toymoban.com/news/detail-474575.html

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