ElasticSearch使用实例

当涉及到Elasticsearch的入门实例时，以下是一个详细的示例，展示了如何使用Java高级REST客户端与Elasticsearch进行交互。

1. 准备工作：
   • 安装Elasticsearch：请按照Elasticsearch官方文档中的说明安装并启动Elasticsearch。
   • 添加依赖项：在您的项目的构建文件（例如pom.xml）中，添加Elasticsearch的Java高级REST客户端的依赖项。例如，在Maven项目中，您可以添加以下依赖项：

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.15.0</version>
</dependency>

2. 创建索引：
   • 创建一个名为"my_index"的索引：

import org.elasticsearch.action.admin.indices.create.CreateIndexRequest;
import org.elasticsearch.action.admin.indices.create.CreateIndexResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.indices.GetIndexRequest;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.xcontent.XContentType;

import java.io.IOException;

public class ElasticsearchDemo {

    public static void main(String[] args) {
        try (RestHighLevelClient client = ElasticsearchClientFactory.createClient()) {
            String indexName = "my_index";

            // 检查索引是否已存在
            boolean indexExists = client.indices().exists(new GetIndexRequest(indexName), RequestOptions.DEFAULT);
            if (!indexExists) {
                // 创建索引请求
                CreateIndexRequest request = new CreateIndexRequest(indexName);

                // 设置索引的设置
                request.settings(Settings.builder()
                        .put("index.number_of_shards", 1)
                        .put("index.number_of_replicas", 1));

                // 设置索引的映射
                String mapping = "{\"properties\":{\"title\":{\"type\":\"text\"},\"content\":{\"type\":\"text\"}}}";
                request.mapping(mapping, XContentType.JSON);

                // 执行创建索引请求
                CreateIndexResponse response = client.indices().create(request, RequestOptions.DEFAULT);

                // 判断索引是否创建成功
                if (response.isAcknowledged()) {
                    System.out.println("Index created: " + indexName);
                } else {
                    System.out.println("Failed to create index: " + indexName);
                }
            } else {
                System.out.println("Index already exists: " + indexName);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3. 添加文档：
   • 向索引中添加一个文档：

import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.action.index.IndexResponse;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.indices.GetIndexRequest;
import org.elasticsearch.common.xcontent.XContentType;

import java.io.IOException;

public class ElasticsearchDemo {

    public static void main(String[] args) {
        try (RestHighLevelClient client = ElasticsearchClientFactory.createClient()) {
            String indexName = "my_index";
            String documentId = "1";

            // 检查索引是否存在
            boolean indexExists = client.indices().exists(new GetIndexRequest(indexName), RequestOptions.DEFAULT);
            if (indexExists) {
                // 创建索引请求
                IndexRequest request = new IndexRequest(indexName)
                        .id(documentId)
                        .source

("{\"title\":\"Elasticsearch Demo\",\"content\":\"This is a demo content\"}", XContentType.JSON);

                // 执行索引请求
                IndexResponse response = client.index(request, RequestOptions.DEFAULT);

                // 打印响应信息
                System.out.println("Index created with ID: " + response.getId());
            } else {
                System.out.println("Index does not exist: " + indexName);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

4. 搜索文档：
   • 从索引中搜索文档：

import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.indices.GetIndexRequest;
import org.elasticsearch.common.unit.TimeValue;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.builder.SearchSourceBuilder;

import java.io.IOException;

public class ElasticsearchDemo {

    public static void main(String[] args) {
        try (RestHighLevelClient client = ElasticsearchClientFactory.createClient()) {
            String indexName = "my_index";

            // 检查索引是否存在
            boolean indexExists = client.indices().exists(new GetIndexRequest(indexName), RequestOptions.DEFAULT);
            if (indexExists) {
                // 创建搜索请求
                SearchRequest request = new SearchRequest(indexName);

                // 构建搜索条件
                SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
                sourceBuilder.query(QueryBuilders.matchQuery("content", "demo"));
                sourceBuilder.timeout(TimeValue.timeValueSeconds(10));
                request.source(sourceBuilder);

                // 执行搜索请求
                SearchResponse response = client.search(request, RequestOptions.DEFAULT);

                // 处理搜索结果
                for (SearchHit hit : response.getHits().getHits()) {
                    System.out.println("Document ID: " + hit.getId());
                    System.out.println("Document Source: " + hit.getSourceAsString());
                    System.out.println("--------------------------------------------------");
                }
            } else {
                System.out.println("Index does not exist: " + indexName);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

以上示例代码中的操作是一个简化的示例，您可以根据您的实际需求进行相应的操作，如创建索引、添加文档、搜索文档等。

在编译和运行代码之前，请确保已添加了Elasticsearch的Java高级REST客户端的依赖项，并根据您的实际情况修改代码中的Elasticsearch服务器的主机、端口和索引名称。

希望以上示例能帮助您入门使用Elasticsearch。如需进一步了解和使用Elasticsearch，请参考官方文档和示例代码。