Java DNSLookup 获取 DNS 属性
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Java DNSLookup get DNS attributes
提问by MikeNQ
I'm quite new to the network DNS records and need a program that can run lookup to get 3 main DNS records of a domain (A,MX,NS).
我对网络 DNS 记录很陌生，需要一个可以运行查找的程序来获取域（A、MX、NS）的 3 个主要 DNS 记录。
I have been looking for a java solution here an there and my final class is as below: However, I will always get a NameExceptionand can't find the reason for it.
我一直在这里和那里寻找一个 java 解决方案，我的最后一课如下： 但是，我总是会得到一个NameException并且找不到它的原因。
[EDIT]: The problem seem to be with our internet, because using other wifi, the program run just fine.
[编辑]：问题似乎出在我们的互联网上，因为使用其他 wifi，程序运行得很好。
Many thanks,
非常感谢，
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;
import javax.naming.Context;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Hashtable;
public class DNSLookup
{
public static void main(String args[])
{
String host = "google.com";
try
{
InetAddress inetAddress = InetAddress.getByName(host);
// show the Internet Address as name/address
System.out.println(inetAddress.getHostName() + " " + inetAddress.getHostAddress());
Hashtable<String, String> env = new Hashtable<String, String>();
//env.put(Context.INITIAL_CONTEXT_FACTORY,"com.sun.jndi.ldap.LdapCtxFactory");
//env.put(Context.PROVIDER_URL, "ldap://localhost:389/o=JNDITutorial");
env.put(Context.INITIAL_CONTEXT_FACTORY,"com.sun.jndi.dns.DnsContextFactory");
//env.put(Context.PROVIDER_URL, "dns://google.com");
// get the default initial Directory Context
InitialDirContext iDirC = new InitialDirContext(env);
// get the DNS records for inetAddress
Attributes attributes = iDirC.getAttributes("dns:/"+inetAddress.getHostName());
// get an enumeration of the attributes and print them out
NamingEnumeration<?> attributeEnumeration = attributes.getAll();
System.out.println("");
while (attributeEnumeration.hasMore())
{
System.out.println("" + attributeEnumeration.next());
}
attributeEnumeration.close();
}
catch (UnknownHostException exception)
{
System.err.println("ERROR: Cannot access '" + host + "'");
}
catch (NamingException exception)
{
System.err.println("ERROR: No DNS record for '" + host + "'");
exception.printStackTrace();
}
}
}
Output:
输出：
google.com 74.125.128.113
ERROR: No DNS record for 'google.com'
javax.naming.CommunicationException: DNS error [Root exception is java.net.SocketTimeoutException: Receive timed out]; remaining name 'google.com'
at com.sun.jndi.dns.DnsClient.query(Unknown Source)
at com.sun.jndi.dns.Resolver.query(Unknown Source)
at com.sun.jndi.dns.DnsContext.c_getAttributes(Unknown Source)
at com.sun.jndi.toolkit.ctx.ComponentDirContext.p_getAttributes(Unknown Source)
at com.sun.jndi.toolkit.ctx.PartialCompositeDirContext.getAttributes(Unknown Source)
at com.sun.jndi.toolkit.url.GenericURLDirContext.getAttributes(Unknown Source)
at javax.naming.directory.InitialDirContext.getAttributes(Unknown Source)
at javax.naming.directory.InitialDirContext.getAttributes(Unknown Source)
at gimasys.dnsCrawler.DNSLookup.main(DNSLookup.java:35)
Caused by: java.net.SocketTimeoutException: Receive timed out
at java.net.DualStackPlainDatagramSocketImpl.socketReceiveOrPeekData(Native Method)
at java.net.DualStackPlainDatagramSocketImpl.receive0(Unknown Source)
at java.net.AbstractPlainDatagramSocketImpl.receive(Unknown Source)
at java.net.DatagramSocket.receive(Unknown Source)
at com.sun.jndi.dns.DnsClient.doUdpQuery(Unknown Source)
... 9 more
回答by NPKR
I have tried with provided class (DNSLookup.java), it's working for me.
我试过提供的类 ( DNSLookup.java)，它对我有用。
My underestanding is it's giving timeOut exception, means its not able to connect to server.
我的理解是它给出了超时异常，这意味着它无法连接到服务器。
Check your internet connection ?
