03. Elasticsearch - Java를 이용하여 Get Request

01) Dependency 설정

 

Spring boot 프로젝트 하나 만들어 테스트.

 

Elasticsearch 디펜던시 추가.

 

<!-- Elastic Search -->
<dependency>
	<groupId>org.elasticsearch</groupId>
	<artifactId>elasticsearch</artifactId>
	<version>7.12.1</version>
</dependency>
<dependency>
	<groupId>org.elasticsearch.client</groupId>
	<artifactId>elasticsearch-rest-high-level-client</artifactId>
	<version>7.12.1</version>
</dependency>

 

High level client는 Low level client를 한번 추상화해서 사용.

 

Low level client는 버전에 영향을 받지 않고 유연하지만 사용하기는 더 어려움.

 

https://www.elastic.co/guide/en/elasticsearch/client/java-rest/master/java-rest-high.html

Java High Level REST Client | Java REST Client [master] | Elastic

 

홈페이지를 통해 API를 확인할 수 있음.

 

@SpringBootApplication
public class ElasticsearchTestApplication {

	public static void main(String[] args) throws IOException {
		SpringApplication.run(ElasticsearchTestApplication.class, args);
		
		String hostname = "localhost";
		int port = 9200;
		HttpHost host = new HttpHost(hostname, port);
		System.out.println(host);
		RestClientBuilder restClientBuilder = RestClient.builder(host);
		RestHighLevelClient client = new RestHighLevelClient(restClientBuilder);
		
		String index = "gaia";
		String id = "1";
		GetRequest getRequest = new GetRequest(index, id);
		RequestOptions options = RequestOptions.DEFAULT;
		
		GetResponse response = client.get(getRequest, options);
		
		Map<String, Object> map = response.getSourceAsMap();
		System.out.println(map);
	}

}

 

해당 GetRequest를 통해 이전에 gaia Index에 1번 ID로 넣었던 데이터를 가져올 수 있었음.

 

 

싱글톤 패턴으러 ElasticUtil 만들어 호출해보기.

 

package com.example.demo;

import java.io.IOException;
import java.io.Reader;
import java.util.Map;
import java.util.Properties;

import org.apache.http.HttpHost;
import org.apache.ibatis.io.Resources;
import org.elasticsearch.action.get.GetRequest;
import org.elasticsearch.action.get.GetResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.client.RestHighLevelClient;

public class ElasticUtil {
	
	private static ElasticUtil self;
	private static RestHighLevelClient client;
	
	private ElasticUtil() throws IOException {
		
        Properties properties = new Properties();
        Reader reader = Resources.getResourceAsReader("el.properties");
        properties.load(reader);
        String hostname = properties.getProperty("el.url");
        int port = Integer.parseInt(properties.getProperty("el.port"));
        HttpHost host = new HttpHost(hostname, port);
        RestClientBuilder restClientBuilder = RestClient.builder(host);
        client = new RestHighLevelClient(restClientBuilder);
        
	}
	
	public static ElasticUtil getInstance() throws IOException {
		
		if(self == null)
			self = new ElasticUtil();
		return self;
		
	}
	
	public Map<String,Object> getReponse(String index, String id) {
		
		GetResponse response = null; 
		
		GetRequest getRequest = new GetRequest(index, id);
		RequestOptions options = RequestOptions.DEFAULT;
		try {
		response = client.get(getRequest, options);
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		return response.getSourceAsMap();
		
	}
	
}

 

 

src/main/resources 밑에 el.properties 파일을 만들고 url 및 port 정보 저장.

 

ElasticsearchTestApplication.java 에서 다음과 같이 호출.

 

package com.example.demo;

import java.io.IOException;
import java.util.Map;

import org.apache.http.HttpHost;
import org.elasticsearch.action.get.GetRequest;
import org.elasticsearch.action.get.GetResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.client.RestHighLevelClient;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class ElasticsearchTestApplication {

	public static void main(String[] args) throws IOException {
		
		String index = "gaia";
		String id = "1";
		
		ElasticUtil elastic = ElasticUtil.getInstance();
		
		Map<String, Object> map = elastic.getReponse(index, id);
		
		System.out.println(map);
		
	}

}