This article demonstrates how to manage Elasticsearch using the High-Level REST Client. It covers connecting to a Elasticsearch cluster, creating indices, and checking their existence.

The following example shows how to establish a connection with basic authentication and perform operations like index creation:

import org.apache.http.Header; import org.apache.http.HttpHost; import org.apache.http.auth.AuthScope; import org.apache.http.auth.UsernamePasswordCredentials; import org.apache.http.client.CredentialsProvider; import org.apache.http.impl.client.BasicCredentialsProvider; import org.apache.http.impl.nio.client.HttpAsyncClientBuilder; import org.apache.http.util.EntityUtils; import org.elasticsearch.action.admin.indices.create.CreateIndexRequest; import org.elasticsearch.action.admin.indices.create.CreateIndexResponse; import org.elasticsearch.action.admin.indices.get.GetIndexRequest; import org.elasticsearch.client.*; import org.elasticsearch.common.settings.Settings; import org.elasticsearch.common.xcontent.XContentType;

import java.io.IOException; import java.text.SimpleDateFormat; import java.util.Date; import java.util.HashMap; import java.util.Map;

public class ESTest {

public static void main(String[] args) throws IOException {
    String user = "admin";
    String pwd = "admin123";
    String host = "192.168.49.131";
    int portNum = 9200;

    final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();

    credentialsProvider.setCredentials(AuthScope.ANY,
            new UsernamePasswordCredentials(user, pwd));

    RestClientBuilder builder = RestClient.builder(new HttpHost(host, portNum));

    builder.setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
        public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
            httpClientBuilder.disableAuthCaching();
            return httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
        }
    });
    RestClient restClient = builder.build();

    RestHighLevelClient highLevelClient = new RestHighLevelClient(builder);

    Request req = new Request(
            "GET",
            "_cat/indices?v");
    Response res = restClient.performRequest(req);
    HttpHost hostInfo = res.getHost();
    int statusCode = res.getStatusLine().getStatusCode();
    Header[] headers = res.getHeaders();
    String body = EntityUtils.toString(res.getEntity());

    String indexName = "es-demo-" + getCurrentDate();

    try {
        createIndex(highLevelClient, indexName);
    } catch (Exception e){
        e.printStackTrace();
    }


    restClient.close();
    highLevelClient.close();
}

/**
 * Checks if an index already exists
 *
 * @param client Elasticsearch client instance
 * @param indexName Name of the index to check
 * @return true if index exists, false otherwise
 * @throws Exception if operation fails
 */
public static boolean doesIndexExist(RestHighLevelClient client, String indexName) throws Exception {
    GetIndexRequest request = new GetIndexRequest();
    request.indices(indexName);
    request.local(false);
    request.humanReadable(true);

    boolean exists = client.indices().exists(request);
    return exists;
}

/**
 * Creates an index with specified mappings
 *
 * @param client Elasticsearch client instance
 * @param indexName Name of the index to create
 * @param type Document type (deprecated in newer versions)
 * @param fields Field definitions for the index
 * @return true if index was created successfully
 * @throws Exception if operation fails
 */
public static boolean createIndex(RestHighLevelClient client, String indexName, String type,
                           Map<string object=""> fields) throws Exception {

    if (doesIndexExist(client, indexName)) {
        return true;
    }
    CreateIndexRequest request = new CreateIndexRequest(indexName);
    request.settings(Settings.builder().put("index.number_of_shards", 3)
            .put("index.number_of_replicas", 1));

    Map<string object=""> jsonMap = new HashMap<>();
    Map<string object=""> mapping = new HashMap<>();
    mapping.put("properties", fields);
    jsonMap.put(type, mapping);
    request.mapping(type, jsonMap);

    CreateIndexResponse createIndexResponse = client.indices().create(
            request, RequestOptions.DEFAULT);
    boolean acknowledged = createIndexResponse.isAcknowledged();
    return acknowledged;
}

/**
 * Creates an index using JSON string mapping
 *
 * @param client Elasticsearch client instance
 * @param indexName Name of the index to create
 * @return true if index was created successfully
 * @throws Exception if operation fails
 */
public static boolean createIndexWithJson(RestHighLevelClient client, String indexName)
                            throws Exception {
    if (doesIndexExist(client, indexName)) {
        return true;
    }

    CreateIndexRequest request = new CreateIndexRequest(indexName);
    request.settings(Settings.builder()
            .put("index.number_of_shards", 3)
            .put("index.number_of_replicas", 1)
    );
    request.mapping("_doc",
            "{\n" +
                    "  \"_doc\": {\n" +
                    "    \"properties\": {\n" +
                    "      \"message\": {\n" +
                    "        \"type\": \"text\"\n" +
                    "      }\n" +
                    "    }\n" +
                    "  }\n" +
                    "}",
            XContentType.JSON);
    CreateIndexResponse createIndexResponse = client.indices().create(
            request, RequestOptions.DEFAULT);
    boolean acknowledged = createIndexResponse.isAcknowledged();
    return acknowledged;
}

public static String getCurrentDate() {
    Date currentDate = new Date();
    SimpleDateFormat formatter = new SimpleDateFormat("yyyy.MM.dd");
    return formatter.format(currentDate);
}

}

</div>Maven dependencies required for this setup:

<div>```
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.4.RELEASE</version>
        <relativePath/>
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo-es</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo-es</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <dependency>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
            <version>6.4.3</version>
        </dependency>

        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>elasticsearch-rest-high-level-client</artifactId>
            <version>6.4.3</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>