Elasticsearch 在 Java 中的使用示例教程_Java

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。

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Elasticsearch 在 Java 中的使用示例教程

2024年08月20日 • Java •我要评论