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Elasticsearch 在 Java 中的使用示例教程

开发者 https://www.devze.com 2024-08-21 10:28 出处:网络 作者: boydoy1987
目录1. Elasticsearch 简介2. 环境准备2.1 安装 Elasticsearch2.2 Java 开发环境配置2.3 添加 Elasticsearch 客户端依赖3. 使用 Java 连接 Elasticsearch3.1 编写连接代码3.2 运行代码4. 基本 CRUD 操作4.1 创建索引
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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