elasticsearch, kibana, 6.8.18 版本下的创建索引，指定timestamp，java CRUD，maven版本等

在Elasticsearch 6.8.18版本下，使用Java客户端创建索引并指定时间戳字段，可以通过以下步骤实现：

1. 在Maven项目的pom.xml中添加Elasticsearch依赖：

<dependencies>
    <!-- Elasticsearch客户端 -->
    <dependency>
        <groupId>org.elasticsearch.client</groupId>
        <artifactId>elasticsearch-rest-high-level-client</artifactId>
        <version>6.8.18</version>
    </dependency>
    <!-- Elasticsearch核心 -->
    <dependency>
        <groupId>org.elasticsearch</groupId>
        <artifactId>elasticsearch</artifactId>
        <version>6.8.18</version>
    </dependency>
</dependencies>

2. 创建索引并指定时间戳字段的Java代码：

import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.common.xcontent.XContentType;
import org.elasticsearch.ElasticsearchStatusException;
import org.elasticsearch.action.admin.indices.create.CreateIndexRequest;
 
import java.io.IOException;
 
public class ElasticsearchExample {
 
    public static void main(String[] args) throws IOException {
        // 初始化Elasticsearch客户端
        RestClientBuilder builder = RestClient.builder(new HttpHost("localhost", 9200, "http"));
        RestHighLevelClient client = new RestHighLevelClient(builder);
 
        // 创建CreateIndexRequest
        CreateIndexRequest request = new CreateIndexRequest("my_index");
 
        // 设置索引的mappings，包括时间戳字段
        String jsonMappings = "{\n" +
                "  \"mappings\": {\n" +
                "    \"_doc\": {\n" +
                "      \"_source\": {\n" +
                "        \"enabled\": false\n" +
                "      },\n" +
                "      \"properties\": {\n" +
                "        \"@timestamp\": {\n" +
                "          \"type\": \"date\",\n" +
                "          \"format\": \"strict_date_optional_time||epoch_millis\"\n" +
                "        }\n" +
                "      }\n" +
                "    }\n" +
                "  }\n" +
                "}";
        request.mapping("_doc", jsonMappings, XContentType.JSON);
 
        // 创建索引
        try {
            client.indices().create(request, RequestOptions.DEFAULT);
            System.out.println("I