Elasticsearch 在 Java 中的使用教程

目录

Elasticsearch 简介环境准备使用 Java 连接 Elasticsearch基本 CRUD 操作复杂查询操作索引管理与优化聚合操作总结

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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 getRequest = 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        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, "http")).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();        RestClientTransport 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 (deleteIndexResponse.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。