DNSJava demo

DnsTest.java

package com.lansent.demo;

import org.junit.Assert;
import org.junit.Test;
import org.xbill.DNS.*;

import java.io.IOException;
import java.net.InetAddress;

/**
 * @author <a href="mailto:hyysguyang@gmail.com">Young Gu</a>
 * @author <a href="mailto:guyang@lansent.com">Young Gu</a>
 * @Date 8/10/16 10:06 PM
 */


public class DnsTest {

    @Test
    public void testCustomizedDNS() throws IOException {
	String ipFromSystemDNS = resolveHostWithSystemDNS();
	ARecord ipFromCustomizedDNS = resolveHostWithCustomizedDNS("bing.com", "8.8.8.8");
	Assert.assertEquals(ipFromSystemDNS,ipFromCustomizedDNS.getAddress().getHostAddress());
    }

    private String resolveHostWithSystemDNS() {
	try {
	    return InetAddress.getByName("bing.com").getHostAddress();
	} catch (Exception e) {
	    e.printStackTrace();
	    return "";
	}
    }

    private ARecord resolveHostWithCustomizedDNS(String host, String dnsServer) throws IOException {
	final Name full = Name.concatenate(Name.fromString(host), Name.root);
	final Resolver res = new SimpleResolver(dnsServer);
	res.setTimeout(500);
	final Record question = Record.newRecord(full, Type.A, DClass.IN);
	final Message response = res.send(Message.newQuery(question));
	final RRset[] answer = response.getSectionRRsets(Section.ANSWER);
	return (ARecord)answer[0].rrs().next();
    }
}