JAVA HTTP Client Sample codes

java-http-client-samples.md

JAVA HTTP Client Sample codes

HttpURLConnection

/**
 * @see https://docs.oracle.com/javase/8/docs/api/java/net/URLConnection.html
 * @see https://docs.oracle.com/javase/8/docs/api/java/net/HttpURLConnection.html
 * @see https://www.baeldung.com/java-http-request
 */

import java.net.*;
import java.io.*;

public class HttpClient {
	public static void main (String[] args) throws Exception {

		try {
			URL url = new URL("http://www.google.com/");
			HttpURLConnection con = (HttpURLConnection) url.openConnection();

//			con.setRequestMethod("GET");
//			con.setRequestProperty("Content-Type", "application/json");
//			con.setConnectTimeout(5000);
//			con.setReadTimeout(20000);

			BufferedReader in = new BufferedReader(
					new InputStreamReader(
							con.getInputStream()));
			String inputLine;

			while ((inputLine = in.readLine()) != null)
				System.out.println(inputLine);
			in.close();

		} catch (MalformedURLException e) {
			System.out.println("The specified URL is malformed: " + e.getMessage());
		} catch (IOException e) {
			System.out.println("An I/O error occurs: " + e.getMessage());
		}
	}
}

Apache HttpClient

Apache HttpComponents

version: 4.x

import org.apache.http.HttpEntity;
import org.apache.http.client.config.RequestConfig;
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.HttpClientBuilder;
import org.apache.http.util.EntityUtils;
import java.io.IOException;

public class ApacheHttpClient {
	public static void main(String[] args) {
		RequestConfig config = RequestConfig.custom()
//				.setConnectTimeout(5000)
//				.setConnectionRequestTimeout(5000)
//				.setSocketTimeout(20000)
				.build();

		try (final CloseableHttpClient httpclient =
					 HttpClientBuilder.create().setDefaultRequestConfig(config).build()) {
			final HttpGet httpget = new HttpGet("http://www.yidas.com");

//			System.out.println("Executing request " + httpget.getMethod() + " " + httpget.getURI());

			CloseableHttpResponse response = httpclient.execute(httpget);
			HttpEntity entity = response.getEntity();
			String responseBody = EntityUtils.toString(entity);

			System.out.println(responseBody);
		} catch (IOException e) {
			System.out.println(e.getMessage());
		}
	}
}

Spring RestTemplate

Package org.springframework.boot:spring-boot-starter-web

This HTTP client is based on Apache HttpClient

import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;

public class SpringHttpClient {
	public static void main(String[] args) {
		final HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory();
		requestFactory.setConnectTimeout(000);
		RestTemplate restTemplate=new RestTemplate(requestFactory);
		String responseBody = restTemplate.getForObject("http://dns.yidas.com", String.class);
		System.out.println(responseBody);
	}
}