Email Address Validation

[bhuvan sundar]

Hi Ranchers,

I'm using SMTP in my java class to send mail. I need to verify/validate the email address entered by the user before sending a mail to that address.

Is there any way to validate the address which is out of the domain where my SMTP server exists?

Please help me ASAP...Thanks in advance

[Rashid Mayes]

Hi, I am not sure if you found and answer...

Do you want to know if the address is well formed or the domain of the address is valid, i.e. exists, has an MX record, etc.?

[Gerardo Tasistro]

I use a PERL script to check and parse DNS records. It would be great to know how to do that directly with Java. Maybe some naming class or some method in the URL tools.

[Rashid Mayes]

You can use the DnsContextFactory to perform MX lookups. If you search for DnsContextFactory on java.sun.com you will find some pretty good examples. Start there. In the meantime here is a quick example of getting select records for an IP.

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.Hashtable;
import java.util.LinkedList;
import java.util.List;
 
import javax.naming.Context;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;
 
import com.astrientlabs.prefs.Preferences;
 

public class HostInfo
{
    private static DirContext ictx = null;
    
    private String type;
    private String name;
    private String value;
    
 
    private HostInfo()
    {
        
    }
    
    public static HostInfo[] getHostInfo(String host) throws NamingException
    {
        if ( ictx == null )
        {
            Hashtable env = new Hashtable();
            env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.dns.DnsContextFactory");
            env.put(Context.PROVIDER_URL,Preferences.system.get("dns.url","dns://192.168.0.1"));
            env.put("com.sun.jndi.dns.timeout.initial", "2000");
            env.put("com.sun.jndi.dns.timeout.retries", "3");
            ictx = new InitialDirContext(env);
        }
        
        List info = new LinkedList();
        
        
        String[] types =  { "A", "NS", "CNAME", "SOA", "PTR", "MX", "TXT", "HINFO", "AAAA", "NAPTR", "SRV" };
        String id;
        
 
            Attributes attrs = ictx.getAttributes(host, types);
            Attribute attr;
            HostInfo hostInfo;
            for (NamingEnumeration ne = attrs.getIDs(); ne.hasMore(); )
            {
                attr = attrs.get(ne.next().toString());
                
                hostInfo = new HostInfo();
                hostInfo.type = attr.getID();
                hostInfo.name = attr.getID();
                //TODO: recurse into attributes
                hostInfo.value = String.valueOf(attr);
                info.add(hostInfo);
            }
        
 
        
        return (HostInfo[])info.toArray(new HostInfo[info.size()]);
    }
    
    public void printAttributes(String type, String host) throws NamingException
    {
 
    }
    
    public static void main(String[] args)
    {
        try
        {   
            HostInfo[] info = getHostInfo("yahoo.com");
            for ( int i = 0; i < info.length; i++ )
            {
                System.out.println(info[i].value);
            }
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        
        System.exit(0);
    }
}

The NetworkInterface and InetAddress classes are usefull also. Look at the methods

InetAddress.getAllByName()
InetAddress.getByName()
InetAddress.isReachable()


Last but not least, you can use sockets to perfom whois lookups directly.

[Gerardo Tasistro]

Ok here is a quick and dirty validator. Gets the email string, validates it. If ok it returns the email if DNS lookup fails returns "<< email >>". Thus resetting the field. This is an AJAX call on the server so it isn't a real validator per see ala JSF or JSP style.

 
public String validateEmail(String email) {
try {
                        // split email at the @
String[] domain=email.split("@");
if (domain.length==2) {
                        // if split into two parts, then there is hope, DNS it
InetAddress.getByName(domain[1]);
} else {
                        // not 2 parts, then more @ than needed or too few, don't even DNS it
return "<< email >>";
}
} catch (UnknownHostException e) {
 
// if DNS creates exception it means the domain is no good, return << email >>
e.printStackTrace();
return "<< email >>";

}
return email;
}