Elasticsearch 在 Java 中的使用示例教程

更新時間：2024年08月20日 12:22:20 作者：boydoy1987

本文介紹了如何在Java中使用Elasticsearch,涵蓋了連接、基本CRUD 操作、復(fù)雜查詢、索引管理和聚合操作等方面的內(nèi)容,通過示例,開發(fā)者可以一步步地掌握如何在 Java 項目中集成 Elasticsearch,并利用其強(qiáng)大的搜索和分析功能來構(gòu)建高效的應(yīng)用程序,感興趣的朋友一起看看吧

1. Elasticsearch 簡介

Elasticsearch 是一個分布式搜索和分析引擎，基于 Apache Lucene 構(gòu)建，能夠?qū)崿F(xiàn)實時數(shù)據(jù)的存儲、搜索、和分析。它廣泛應(yīng)用于全文搜索、日志分析、性能監(jiān)控等領(lǐng)域。Elasticsearch 的核心概念包括文檔（document）、索引（index）、和分片（shard）。

2. 環(huán)境準(zhǔn)備

2.1 安裝 Elasticsearch

從 Elasticsearch 官方網(wǎng)站下載并安裝適合你操作系統(tǒng)的版本。

安裝完成后，通過以下命令啟動 Elasticsearch 服務(wù)：

./bin/elasticsearch

默認(rèn)情況下，Elasticsearch 運(yùn)行在 http://localhost:9200。

2.2 Java 開發(fā)環(huán)境配置

安裝 Java SDK（JDK 11 或更高版本）。
安裝 Maven 或 Gradle。
創(chuàng)建一個 Maven 項目，添加 Elasticsearch Java 客戶端的依賴。

2.3 添加 Elasticsearch 客戶端依賴

在 Maven 項目的 pom.xml 文件中添加以下依賴：

<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 文件中添加以下依賴：

dependencies {
    implementation 'co.elastic.clients:elasticsearch-java:8.10.0'
}

添加依賴后，確保項目能夠正常編譯。

3. 使用 Java 連接 Elasticsearch

接下來，我們將編寫一個簡單的 Java 程序來連接 Elasticsearch。

3.1 編寫連接代碼

創(chuàng)建一個 Java 類，例如 ElasticsearchConnection.java，并編寫以下代碼：

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 {
        // 創(chuàng)建 REST 客戶端
        RestClient restClient = RestClient.builder(
                new HttpHost("localhost", 9200, "http")).build();
        // 創(chuàng)建傳輸層
        RestClientTransport transport = new RestClientTransport(
                restClient, new JacksonJsonpMapper());
        // 創(chuàng)建 Elasticsearch 客戶端
        ElasticsearchClient client = new ElasticsearchClient(transport);
        // 獲取集群信息
        InfoResponse info = client.info();
        System.out.println("Connected to Elasticsearch cluster: " + info.clusterName());
        // 關(guān)閉客戶端
        transport.close();
    }
}

3.2 運(yùn)行代碼

編譯并運(yùn)行這個程序，如果成功，你將看到類似如下的輸出：

Connected to Elasticsearch cluster: elasticsearch

這表明你已經(jīng)成功連接到了 Elasticsearch。

4. 基本 CRUD 操作

Elasticsearch 的 CRUD 操作主要涉及對索引中的文檔進(jìn)行增（Create）、查（Read）、改（Update）、刪（Delete）操作。

4.1 創(chuàng)建索引和插入文檔

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 {
        // 創(chuàng)建 REST 客戶端
        RestClient restClient = RestClient.builder(
                new HttpHost("localhost", 9200, "http")).build();
        // 創(chuàng)建傳輸層
        RestClientTransport transport = new RestClientTransport(
                restClient, new JacksonJsonpMapper());
        // 創(chuàng)建 Elasticsearch 客戶端
        ElasticsearchClient client = new ElasticsearchClient(transport);
        // 創(chuàng)建文檔
        String json = "{ \"name\": \"John Doe\", \"age\": 30, \"city\": \"New York\" }";
        // 插入文檔到索引
        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());
        // 關(guān)閉客戶端
        transport.close();
    }
}

4.2 查詢文檔

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);
        // 查詢文檔
        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 更新文檔

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);
        // 更新文檔
        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 刪除文檔

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);
        // 刪除文檔
        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. 復(fù)雜查詢操作

Elasticsearch 提供了強(qiáng)大的查詢 DSL（Domain Specific Language），支持布爾查詢、范圍查詢、聚合查詢等。

5.1 布爾查詢

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);
        // 布爾查詢
        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 范圍查詢

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);
        // 范圍查詢：查詢 age 在 25 到 35 之間的文檔
        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. 索引管理與優(yōu)化

在 Elasticsearch 中，索引管理是非常重要的操作，合理的索引設(shè)置和優(yōu)化可以大幅提升查詢性能。

6.1 創(chuàng)建索引并設(shè)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);
        // 創(chuàng)建索引并設(shè)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 刪除索引

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);
        // 刪除索引
        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 的聚合功能非常強(qiáng)大，能夠?qū)?shù)據(jù)進(jìn)行分組統(tǒng)計、計算平均值、最大值、最小值等操作。

7.1 聚合查詢：計算年齡的平均值

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);
        // 聚合查詢：計算年齡的平均值
        SearchRequest searchRequest = new SearchRequest.Builder()
                .index("users")
                .size(0)  // 不返回文檔，只返回聚合結(jié)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. 總結(jié)

本教程詳細(xì)介紹了如何在 Java 中使用 Elasticsearch，涵蓋了連接、基本 CRUD 操作、復(fù)雜查詢、索引管理和聚合操作等方面的內(nèi)容。通過這些示例，開發(fā)者可以一步步地掌握如何在 Java 項目中集成 Elasticsearch，并利用其強(qiáng)大的搜索和分析功能來構(gòu)建高效的應(yīng)用程序。

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