Elasticsearch 在 Java 中的使用示例教程
目录
- 1. Elasticsearch 简介
- 2. 环境准备
- 2.1 安装 Elasticsearch
- 2.2 Java 开发环境配置
- 2.3 添加 Elasticsearch 客户端依赖
- 3. 使用 Java 连接 Elasticsearch
- 3.1 编写连接代码
- 3.2 运行代码
- 4. 基本 CRUD 操作
- 4.1 创建索引和插入文档
- 4.2 查询文档
- 4.3 更新文档
- 4.4 删除文档
- 5. 复杂查询操作
- 5.1 布尔查询
- 5.2 范围查询
- 6. 索引管理与优化
- 6.1 创建索引并设置映射
- 6.2 删除索引
- 7. 聚合操作
- 7.1 聚合查询:计算年龄的平均值
- 8. 总结
1. Elasticsearch 简介
Elasticsearch 是一个分布式搜索和分析引擎,基于 Apache Lucene 构建,能够实现实时数据的存储、搜索、和分析。它广泛应用于全文搜索、日志分析、性能监控等领域。Elasticsearch 的核心概念包括文档(document)、索引(index)、和分片(shard)。
2. 环境准备
2.1 安装 Elasticsearch
从 Elasticsearch 官方网站 下载并安装适合你操作系统的版本。
安装完成后,通过以下命令启动 Elasticsearch 服务:
./bin/elasticsearch
默认情况下,Elasticsearch 运行在 http://localhost:9200
。
2.2 Java 开发环境配置
- 安装 Java SDK(JDK 11 或更高版本)。
- 安装 Maven 或 Gradle。
- 创建一个 Maven 项目,添加 Elasticsearch Java 客户端的依赖。
2.3 添加 Elasticsearch 客户端依赖
在 Maven 项目的 pom.XML
文件中添加以下依赖:
<dependencies> <!-- Elasticsearch Java Client --> <dependency> <groupId>co.elastic.clients</groupId> <artifactId>elasticsearch-java</artifactId> <version>8.10.0</version> </dependency> </dependencies>
如果你使用 Gradle,可以在 build.gradle
文件中添加以下依赖:
dependencies { implementation 'co.elastic.clients:elasticsearch-java:8.10.0' }
添加依赖后,确保项目能够正常编译。
3. 使用 Java 连接 Elasticsearch
接下来,我们将编写一个简单的 Java 程序来连接 Elasticsearch。
3.1 编写连接代码
创建一个 Java 类,例如 ElasticsearchConnection.java
,并编写以下代码:
import co.elastic.clients.elasticsearch.ElasticsearchClient; import co.elastic.clients.elasticsearch.core.InfoResponse; import co.elastic.clients.transport.rest_client.RestClientTransport; import co.elastic.clients.json.jackson.JacksonJsonpMapper; import org.apache.http.HttpHost; import org.elasticsearch.client.RestClient; public class ElasticsearchConnection { public static void main(String[] args) throws Exception { // 创建 REST 客户端 RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200, "http")).build(); // 创建传输层 RestClientTransport transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); // 创建 Elasticsearch 客户端 ElasticsearchClient client = new ElasticsearchClient(transport); // 获取集群信息 InfoResponse info = client.info(); System.out.println("Connected to Elasticsearch cluster: " + info.clusterName()); // 关闭客户端 transport.close(); } }
3.2 运行代码
编译并运行这个程序,如果成功,你将看到类似如下的输出:
Connected to Elasticsearch cluster: elasticsearch
这表明你已经成功连接到了 Elasticsearch。
4. 基本 CRUD 操作
Elasticsearch 的 CRUD 操作主要涉及对索引中的文档进行增(Create)、查(Read)、改(Update)、删(Delete)操作。
4.1 创建索引和插入文档
import co.elastic.clients.elasticsearch.ElasticsearchClient; import co.elastic.clients.elasticsearch.core.IndexResponse; import co.elastic.clients.transport.rest_client.RestClientTransport; import co.elastic.clients.json.jackson.JacksonJsonpMapper; import org.apache.http.HttpHost; import org.elasticsearch.client.RestClient; import co.elastic.clients.elasticsearch.core.IndexRequest; public class ElasticsearchCRUD { public static void main(String[] args) throws Exception { // 创建 REST 客户端 RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200, "http")).build(); // 创建传输层 RestClientTransport transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); // 创建 Elasticsearch 客户端 ElasticsearchClient client = new ElasticsearchClient(transport); // 创建文档 String json = "{ \"name\": \"John Doe\", \"age\": 30, \"city\": \"New York\" }"; // 插入文档到索引 IndexRequest<Object> request = new IndexRequest.Builder<>() .index("users") .id("1") .document(json) .build(); IndexResponse response = client.index(request); System.out.println("Document inserted with ID: " + response.id()); // 关闭客户端 transport.close(); } }
4.2 查询文档
import co.elastic.clients.elasticsearch.ElasticsearchClient; import co.elastic.clients.elasticsearch.core.GetResponse; import co.elastic.clients.transport.rest_client.RestClientTransport; import co.elastic.clients.json.jackson.JacksonJsonpMapper; import org.apache.http.HttpHost; import org.elasticsearch.client.RestClient; import co.elastic.clients.elasticsearch.core.GetRequest; public class ElasticsearchRead { public static void main(String[] args) throws Exception { RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200, "http")).build(); RestClientTransport transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); ElasticsearchClient client = new ElasticsearchClient(transport); // 查询文档 GetRequest getRphpequest = new GetRequest.Builder() .index("users") .id("1") .build(); GetResponse<Object> response = client.get(getRequest, Object.class); if (response.found()) { System.out.println("Document found: " + response.source()); } else { System.out.println("Document not found"); } transport.close(); } }
4.3 更新文档
import co.elastic.clients.elasticsearch.ElasticsearchClient; import co.elastic.clients.elasticsearch.core.UpdateResponse; import co.elastic.clients.transport.rest_client.RestClientTransport; import co.elastic.clients.json.jackson.JacksonJsonpMapper; import org.apache.http.HttpHost; import org.elasticsearch.client.RestClient; import co.elastic.clients.elasticsearch.core.UpdateRequest; import java.util.Map; public class ElasticsearchUpdate { public static void main(String[] args) throws Exception { RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200, "http")).build(); RestClientTransport transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); ElasticsearchClient client = new ElasticsearchClient(transport); // 更新文档 编程 Map<String, Object> updateJson = Map.of( "age", 31, "city", "San Francisco" ); UpdateRequest<Object, Map<String, Object>> updateRequest = new UpdateRequest.Builder<>() .index("users") .id("1") .doc(updateJson) .build(); UpdateResponse<Object> updateResponse = client.update(updateRequest, Object.class); System.out.println("Document updated: " + updateResponse.result()); transport.close(); } }
4.4 删除文档
import co.elastic.clients.elasticsearch.ElasticsearchClient; import co.elastic.clients.elasticsearch.core.DeleteResponse; import co.elastic.clients.transport.rest_client.RestClientTransport; import co.elastic.clients.json.jackson.JacksonJsonpMapper; import org.apache.http.HttpHost; import org.elasticsearch.client.RestClient; import co.elastic.clients.elasticsearch.core.DeleteRequest; public class ElasticsearchDelete { public static void main(String[] args) throws Exception { RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200, "httwww.devze.comp")).build(); RestClientTransport transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); ElasticsearchClient client = new ElasticsearchClient(transport); // 删除文档 DeleteRequest deleteRequest = new DeleteRequest.Builder() .index("users") .id("1") .build(); DeleteResponse deleteResponse = client.delete(deleteRequest); System.out.println("Document deleted: " + deleteResponse.result()); transport.close(); } }
5. 复杂查询操作
Elasticsearch 提供了强大的查询 DSL(Domain Specific Language),支持布尔查询、范围查询、聚合查询等。
5.1 布尔查询
import co.elastic.clients.elasticsearch.ElasticsearchClient; import co.elastic.clients.elasticsearch.core.SearchResponse; import co.elastic.clients.elasticsearch.core.search.Hit; import co.elastic.clients.transport.rest_client.RestClientTransport; import co.elastic.clients.json.jackson.JacksonJsonpMapper; import org.apache.http.HttpHost; import org.elasticsearch.client.RestClient; import co.elastic.clients.elasticsearch.core.SearchRequest; import co.elastic.clients.elasticsearch.core.search.Query; public class ElasticsearchBooleanQuery { public static void main(String[] args) throws Exception { RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200, "http")).build(); RestClientTransport transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); ElasticsearchClient client = new ElasticsearchClient(transport); // 布尔查询 SearchRequest searchRequest = new SearchRequest.Builder() .index("users") .query(Query .bool(b -> b .must(m -> m.match(match -> match.field("name").query("John Doe"))) .filter(f -> f.range(r -> r.field("age").gte(30))) )) .build(); SearchResponse<Object> searchResponse = client.search(searchRequest, Object.class); for (Hit<Object> hit : searchResponse.hits().hits()) { System.out.println("Document found: " + hit.source()); } transport.close(); } }
5.2 范围查询
import co.elastic.clients.elasticsearch.ElasticsearchClient; import co.elastic.clients.elasticsearch.core.SearchResponse; import co.elastic.clients.elasticsearch.core.search.Hit; import co.elastic.clients.transport.rest_client.RestClientTransport; import co.elastic.clients.json.jackson.JacksonJsonpMapper; import org.apache.http.HttpHost; import org.elasticsearch.client.RestClient; import co.elastic.clients.elasticsearch.core.SearchRequest; import co.elastic.clients.elasticsearch.core.search.Query; public class ElasticsearchRangeQuery { public static void main(String[] args) throws Exception { RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200, "http")).build(); RestClientTransport transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); ElasticsearchClient client = new ElasticsearchClient(transport); // 范围查询:查询 age 在 25 到 35 之间的文档 SearchRequest searchRequest = new SearchRequest.Builder() .index("users") .query(Query.range(r -> r.field("age").gte(25).lte(35))) .build(); SearchResponse<Object> searchResponse = client.search(searchRequest, Object.class); for (Hit<Object> hit : searchResponse.hits().hits()) { System.out.println("Document found: " + hit.source()); } transport.close(); } }
6. 索引管理与优化
在 Elasticsearch 中,索引管理是非常重要的操作,合理的索引设置和优化可以大幅提升查询性能。
6.1 创建索引并设置映射
import co.elastic.clients.elasticsearch.ElasticsearchClient; import co.elastic.clients.elasticsearch.indices.CreateIndexResponse; import co.elastic.clients.transport.rest_client.RestClientTransport; import co.elastic.clients.json.jackson.JacksonJsonpMapper; import org.apache.http.HttpHost; import org.elasticsearch.client.RestClient; import co.elastic.clients.elasticsearch.indices.CreateIndexRequest; public class ElasticsearchCreateIndex { public static void main(String[] args) throws Exception { RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200, "http")).build(); RestClientTranspwww.devze.comort transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); ElasticsearchClient client = new ElasticsearchClient(transport); // 创建索引并设置映射 CreateIndexRequest createIndexRequest = new CreateIndexRequest.Builder() .index("users") .mappings(m -> m .properties("name", p -> p.text(t -> t)) .properties("age", p -> p.integer(i -> i)) .properties("city", p -> p.text(t -> t)) ) .build(); CreateIndexResponse createIndexResponse = client.indices().create(createIndexRequest); if (createIndexResponse.acknowledged()) { System.out.println("Index created successfully!"); } transport.close(); } }
6.2 删除索引
import co.elastic.clients.elasticsearch.ElasticsearchClient; import co.elastic.clients.elasticsearch.indices.DeleteIndexResponse; import co.elastic.clients.transport.rest_client.RestClientTransport; import co.elastic.clients.json.jackson.JacksonJsonpMapper; import org.apache.http.HttpHost; import org.elasticsearch.client.RestClient; import co.elastic.clients.elasticsearch.indices.DeleteIndexRequest; public class ElasticsearchDeleteIndex { public static void main(String[] args) throws Exception { RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200, "http")).build(); RestClientTransport transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); ElasticsearchClient client = new ElasticsearchClient(transport); // 删除索引 DeleteIndexRequest deleteIndexRequest = new DeleteIndexRequest.Builder() .index("users") .build(); DeleteIndexResponse deleteIndexResponse = client.indices().delete(deleteIndexRequest); if (deleteIndexResponsewww.devze.com.acknowledged()) { System.out.println("Index deleted successfully!"); } transport.close(); } }
7. 聚合操作
Elasticsearch 的聚合功能非常强大,能够对数据进行分组统计、计算平均值、最大值、最小值等操作。
7.1 聚合查询:计算年龄的平均值
import co.elastic.clients.elasticsearch.ElasticsearchClient; import co.elastic.clients.elasticsearch.core.SearchResponse; import co.elastic.clients.elasticsearch.core.search.Hit; import co.elastic.clients.elasticsearch.core.search.Aggregation; import co.elastic.clients.elasticsearch.core.search.Bucket; import co.elastic.clients.transport.rest_client.RestClientTransport; import co.elastic.clients.json.jackson.JacksonJsonpMapper; import org.apache.http.HttpHost; import org.elasticsearch.client.RestClient; import co.elastic.clients.elasticsearch.core.SearchRequest; public class ElasticsearchAggregation { public static void main(String[] args) throws Exception { RestClient restClient = RestClient.builder( new HttpHost("localhost", 9200, "http")).build(); RestClientTransport transport = new RestClientTransport( restClient, new JacksonJsonpMapper()); ElasticsearchClient client = new ElasticsearchClient(transport); // 聚合查询:计算年龄的平均值 SearchRequest searchRequest = new SearchRequest.Builder() .index("users") .size(0) // 不返回文档,只返回聚合结果 .aggregations("average_age", a -> a.avg(avg -> avg.field("age"))) .build(); SearchResponse<Object> searchResponse = client.search(searchRequest, Object.class); double averageAge = searchResponse.aggregations().get("average_age").avg().value(); System.out.println("Average age: " + averageAge); transport.close(); } }
8. 总结
本教程详细介绍了如何在 Java 中使用 Elasticsearch,涵盖了连接、基本 CRUD 操作、复杂查询、索引管理和聚合操作等方面的内容。通过这些示例,开发者可以一步步地掌握如何在 Java 项目中集成 Elasticsearch,并利用其强大的搜索和分析功能来构建高效的应用程序。
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