D-Net

package eu.dnetlib.data.utils;

import java.net.URI;

import java.net.URISyntaxException;

import java.security.KeyManagementException;

import java.security.KeyStoreException;

import java.security.NoSuchAlgorithmException;

import java.util.concurrent.TimeUnit;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.apache.http.conn.ssl.SSLConnectionSocketFactory;

import org.apache.http.impl.client.HttpClientBuilder;

import org.apache.http.ssl.SSLContextBuilder;

import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;

import org.springframework.web.client.RestTemplate;

import eu.dnetlib.data.mdstore.plugins.GenericDoiMdstorePlugin;

public class HttpFetcher {

	private static final Log log = LogFactory.getLog(GenericDoiMdstorePlugin.class);

	public static final int MAX_NUMBER_OF_ATTEMPTS = 10;

	private static final int INTERVAL_MILLIS = 20000;

	private static final SSLContextBuilder sslContextBuilder = new SSLContextBuilder();

	private static SSLConnectionSocketFactory sslSocketFactory;

	static {

		try {

			sslContextBuilder.loadTrustMaterial(null, (chain, authType) -> true);

			sslSocketFactory = new SSLConnectionSocketFactory(sslContextBuilder.build());

		} catch (final NoSuchAlgorithmException | KeyStoreException | KeyManagementException e) {

			log.error(e);;

		}

	}

	private static final HttpComponentsClientHttpRequestFactory httpRequestFactory = new HttpComponentsClientHttpRequestFactory(HttpClientBuilder

			.create()

			.setConnectionTimeToLive(0, TimeUnit.MILLISECONDS)

			.setMaxConnPerRoute(1)

			.setMaxConnTotal(1)

			.disableAutomaticRetries()

			.disableConnectionState()

			.setSSLSocketFactory(sslSocketFactory)

			.build());

	public static String fetch(final String url) throws URISyntaxException {

		return fetch(new URI(url), 1);

	}

	public static String fetch(final URI url) {

		return fetch(url, 1);

	}

	public static String fetch(final URI url, final int attempts) {

		if (attempts > MAX_NUMBER_OF_ATTEMPTS) {

			log.error("Max number of attempts reached, downloading url: " + url);

			return "";

		}

		try {

			log.debug("Downloading URL: " + url + " - try: " + attempts);

			return (new RestTemplate(httpRequestFactory)).getForObject(url, String.class);

		} catch (final Throwable e) {

			try {

				log.error("Error downloading url: " + url + " - try: " + attempts + " - " + e.getMessage());

				Thread.sleep(INTERVAL_MILLIS);

				return fetch(url, attempts + 1);

			} catch (final InterruptedException e1) {

				log.error(e);

				return "";

			}

		}

	}

}