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// Copyright (c) 2005 Brian Wellington (bwelling@xbill.org)
package org.xbill.DNS.spi;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.StringTokenizer;
import org.xbill.DNS.AAAARecord;
import org.xbill.DNS.ARecord;
import org.xbill.DNS.ExtendedResolver;
import org.xbill.DNS.Lookup;
import org.xbill.DNS.Name;
import org.xbill.DNS.PTRRecord;
import org.xbill.DNS.Record;
import org.xbill.DNS.Resolver;
import org.xbill.DNS.ReverseMap;
import org.xbill.DNS.TextParseException;
import org.xbill.DNS.Type;
/**
* This class implements a Name Service Provider, which Java can use
* (starting with version 1.4), to perform DNS resolutions instead of using
* the standard calls.
* <p>
* This Name Service Provider uses dnsjava.
* <p>
* To use this provider, you must set the following system property:
* <b>sun.net.spi.nameservice.provider.1=dns,dnsjava</b>
*
* @author Brian Wellington
* @author Paul Cowan (pwc21@yahoo.com)
*/
public class DNSJavaNameService implements InvocationHandler {
private static final String nsProperty = "sun.net.spi.nameservice.nameservers";
private static final String domainProperty = "sun.net.spi.nameservice.domain";
private static final String v6Property = "java.net.preferIPv6Addresses";
private boolean preferV6 = false;
/**
* Creates a DNSJavaNameService instance.
* <p>
* Uses the
* <b>sun.net.spi.nameservice.nameservers</b>,
* <b>sun.net.spi.nameservice.domain</b>, and
* <b>java.net.preferIPv6Addresses</b> properties for configuration.
*/
protected
DNSJavaNameService() {
String nameServers = System.getProperty(nsProperty);
String domain = System.getProperty(domainProperty);
String v6 = System.getProperty(v6Property);
if (nameServers != null) {
StringTokenizer st = new StringTokenizer(nameServers, ",");
String [] servers = new String[st.countTokens()];
int n = 0;
while (st.hasMoreTokens())
servers[n++] = st.nextToken();
try {
Resolver res = new ExtendedResolver(servers);
Lookup.setDefaultResolver(res);
}
catch (UnknownHostException e) {
System.err.println("DNSJavaNameService: invalid " +
nsProperty);
}
}
if (domain != null) {
try {
Lookup.setDefaultSearchPath(new String[] {domain});
}
catch (TextParseException e) {
System.err.println("DNSJavaNameService: invalid " +
domainProperty);
}
}
if (v6 != null && v6.equalsIgnoreCase("true"))
preferV6 = true;
}
public Object
invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
if (method.getName().equals("getHostByAddr")) {
return this.getHostByAddr((byte[]) args[0]);
} else if (method.getName().equals("lookupAllHostAddr")) {
InetAddress[] addresses;
addresses = this.lookupAllHostAddr((String) args[0]);
Class returnType = method.getReturnType();
if (returnType.equals(InetAddress[].class)) {
// method for Java >= 1.6
return addresses;
} else if (returnType.equals(byte[][].class)) {
// method for Java <= 1.5
int naddrs = addresses.length;
byte [][] byteAddresses = new byte[naddrs][];
byte [] addr;
for (int i = 0; i < naddrs; i++) {
addr = addresses[i].getAddress();
byteAddresses[i] = addr;
}
return byteAddresses;
}
}
} catch (Throwable e) {
System.err.println("DNSJavaNameService: Unexpected error.");
e.printStackTrace();
throw e;
}
throw new IllegalArgumentException(
"Unknown function name or arguments.");
}
/**
* Performs a forward DNS lookup for the host name.
* @param host The host name to resolve.
* @return All the ip addresses found for the host name.
*/
public InetAddress []
lookupAllHostAddr(String host) throws UnknownHostException {
Name name = null;
try {
name = new Name(host);
}
catch (TextParseException e) {
throw new UnknownHostException(host);
}
Record [] records = null;
if (preferV6)
records = new Lookup(name, Type.AAAA).run();
if (records == null)
records = new Lookup(name, Type.A).run();
if (records == null && !preferV6)
records = new Lookup(name, Type.AAAA).run();
if (records == null)
throw new UnknownHostException(host);
InetAddress[] array = new InetAddress[records.length];
for (int i = 0; i < records.length; i++) {
Record record = records[i];
if (records[i] instanceof ARecord) {
ARecord a = (ARecord) records[i];
array[i] = a.getAddress();
} else {
AAAARecord aaaa = (AAAARecord) records[i];
array[i] = aaaa.getAddress();
}
}
return array;
}
/**
* Performs a reverse DNS lookup.
* @param addr The ip address to lookup.
* @return The host name found for the ip address.
*/
public String
getHostByAddr(byte [] addr) throws UnknownHostException {
Name name = ReverseMap.fromAddress(InetAddress.getByAddress(addr));
Record [] records = new Lookup(name, Type.PTR).run();
if (records == null)
throw new UnknownHostException();
return ((PTRRecord) records[0]).getTarget().toString();
}
}
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