org.jgroups.protocols.dns.AddressedDNSResolver Maven / Gradle / Ivy

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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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package org.jgroups.protocols.dns;

import org.jgroups.Address;
import org.jgroups.logging.Log;
import org.jgroups.logging.LogFactory;
import org.jgroups.stack.IpAddress;

import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import java.lang.invoke.MethodHandles;
import java.util.ArrayList;
import java.util.List;

public class AddressedDNSResolver extends DefaultDNSResolver {

    private static final Log log = LogFactory.getLog(MethodHandles.lookup().lookupClass());

    public AddressedDNSResolver(DirContext context) {
        super(context);
    }

    public AddressedDNSResolver(String dnsContextFactory, String dnsAddress) throws NamingException {
        super(dnsContextFactory, dnsAddress);
    }

    @Override
    protected List resolveAEntries(String dnsQuery, String srcPort) {
        List addresses = new ArrayList<>();
        try {
            // We are parsing this kind of structure:
            // {a=A: 172.17.0.2, 172.17.0.7}
            // The frst attribute is the type of record. We are not interested in this. Next are addresses.
            Attributes attributes = getDnsContext().getAttributes(dnsQuery, new String[] { DNSRecordType.A.toString() });
            if (attributes != null && attributes.getAll().hasMoreElements()) {
                NamingEnumeration namingEnumeration = attributes.get(DNSRecordType.A.toString()).getAll();
                while (namingEnumeration.hasMoreElements()) {
                    try {
                        int p = Integer.parseInt(srcPort);
                        if (p == 0) {
                            addresses.add(new IpAddress(namingEnumeration.nextElement().toString()));
                        } else {
                            addresses.add(new IpAddress(namingEnumeration.nextElement().toString(), p));
                        }
                    } catch (Exception e) {
                        log.trace("non critical DNS resolution error", e);
                    }
                }
            }
        } catch (NamingException ex) {
            log.trace("no DNS records for query %s, ex: %a", dnsQuery, ex);
        }
        return addresses;
    }
}