HttpClient를 이용해 GET request 보내기

HttpClient를 이용해 GET request 보내기

Apache HttpClient를 이용하면 간편하게 HTTP request를 보낼 수 있습니다.

간혹 웹 서버를 만들면서 다른 서버로 보터 request를 보내 response 받아 데이터를 처리해야

할 때가 있는데 이 때 HttpClient를 이용하면 간단하게 구현 가능합니다.

Mavan을 이용한 dependency 설정

<dependency>
	<groupId>org.apache.httpcomponents</groupId>
	<artifactId>httpclient</artifactId>
	<version>4.4</version>
</dependency>

*Maven과 같은 빌드툴 이용하지 않는다면 https://hc.apache.org/downloads.cgi을 통해 직접 jar파일을 다운 후 

빌드 패스에 추가해주시면 됩니다.

Dependency 설정을 하셨다면 이제 어떤 순서대로 코딩할지 살펴보겠습니다.

1. ClosableHttpClient 인스턴스를 생성

2. HTTP request type에 따른 HttpGet/HttpPost 인스턴스 생성

3. addHeader 메서드를 이용해 헤더정보 추가

4. request를 execute해서 CloseableHttpResponse 얻기

5. response 출력

6. close 메서드를 통해 연결 종료

1. ClosableHttpClient 인스턴스 생성

public class Httpclient1 {
    
    private static final String USER_AGENT = "Mozila/5.0";
    private static final String GET_URL = "http://www.google.com";    
 
    public static void sendGet() throws ClientProtocolException, IOException {
        
        //http client 생성
        CloseableHttpClient httpClient = HttpClients.createDefault();
    }
}

2. HTTP request type에 따른 HttpGet/HttpPost 인스턴스 생성

public class Httpclient1 {
    
    private static final String USER_AGENT = "Mozila/5.0";
    private static final String GET_URL = "http://www.google.com";    
 
    public static void sendGet() throws ClientProtocolException, IOException {
        
        //http client 생성
        CloseableHttpClient httpClient = HttpClients.createDefault();
 
        //get 메서드와 URL 설정
        HttpGet httpGet = new HttpGet(GET_URL);
    }
}

3. addHeader 메서드를 이용해 헤더정보 추가

public class Httpclient1 {
    
    private static final String USER_AGENT = "Mozila/5.0";
    private static final String GET_URL = "http://www.google.com";    
 
    public static void sendGet() throws ClientProtocolException, IOException {
        
        //http client 생성
        CloseableHttpClient httpClient = HttpClients.createDefault();
 
        //get 메서드와 URL 설정
        HttpGet httpGet = new HttpGet(GET_URL);
 
        //agent 정보 설정
        httpGet.addHeader("User-Agent", USER_AGENT);
    }
}

여기까지 했으면 이제는 excute메서드를 통해 request를 보내주고 받은 응답을 처리하면 됩니다.

public class Httpclient1 {
    
    private static final String USER_AGENT = "Mozila/5.0";
    private static final String GET_URL = "http://www.google.com";    
 
    public static void sendGet() throws ClientProtocolException, IOException {
        
        //http client 생성
        CloseableHttpClient httpClient = HttpClients.createDefault();
 
        //get 메서드와 URL 설정
        HttpGet httpGet = new HttpGet(GET_URL);
 
        //agent 정보 설정
        httpGet.addHeader("User-Agent", USER_AGENT);
        
        //get 요청
        CloseableHttpResponse httpResponse = httpClient.execute(httpGet);
        
        System.out.println("::GET Response Status::");
        
        //response의 status 코드 출력
        System.out.println(httpResponse.getStatusLine().getStatusCode());
 
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                httpResponse.getEntity().getContent()));
 
        String inputLine;
        StringBuffer response = new StringBuffer();
 
        while ((inputLine = reader.readLine()) != null) {
            response.append(inputLine);
        }
        
        reader.close();
 
        //Print result
        System.out.println(response.toString());
        httpClient.close();
    }
}

실행결과

*json 데이터를 GET request를 통해 받아와야 하는 경우가 많습니다.

그 때에는 Header 정보인 Content-type에 'application/json'을 추가하고 요청을 보내면 됩니다.

예제코드

import java.io.IOException;
 
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
 
public class httpclient2 {
    
    private static final String USER_AGENT = "Mozila/5.0";
    private static final String GET_URL = "https://blockchain.info/ko"
            + "/rawblock/0000000000000bae09a7a393a8acd"
            + "ed75aa67e46cb81f7acaa5ad94f9eacd103";
    
    public static void sendGet() throws ClientProtocolException, IOException {
        
        //http client 생성
        CloseableHttpClient httpClient = HttpClients.createDefault();
        
        //get 메서드와 URL 설정
        HttpGet httpGet = new HttpGet(GET_URL);
        
        //agent 정보 설정
        httpGet.addHeader("User-Agent", USER_AGENT);
        httpGet.addHeader("Content-type", "application/json");
        
        //get 요청
        CloseableHttpResponse httpResponse = httpClient.execute(httpGet);
        
        System.out.println("GET Response Status");
        System.out.println(httpResponse.getStatusLine().getStatusCode());
        String json = EntityUtils.toString(httpResponse.getEntity(), "UTF-8");
        
        System.out.println(json);
        
        httpClient.close();
    }
}

실행결과

참고 : http://www.journaldev.com/7146/apache-httpclient-example-closeablehttpclient

출처: https://eddyplusit.tistory.com/51 [EddIT]