Is there an easy way to convert String to Inetaddress in Java?

java string inetaddress

20,982

Solution 1

com.google.common.net.InetAddresses.forString(String ipString) is better for this as it will not do a DNS lookup regardless of what string is passed to it.

Solution 2

Yes, that will work. The API is very clear on this ("The host name can either be a machine name, such as "java.sun.com", or a textual representation of its IP address."), and of course you could easily check yourself.

Solution 3

Beware: it seems that parsing an invalid address such as InetAddress.getByName("999.999.999.999") will not result in an exception as one might expect from the documentation's phrase:

the validity of the address format is checked

Empirically, I find myself getting an InetAddress instance with the local machine's raw IP address and the invalid IP address as the host name. Certainly this was not what I expected!

Solution 4

You could try using a regular expression to filter-out non-numeric IP addresses before passing the String to getByName(). Then getByName() will not try name resolution.

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TiansHUo

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Updated on December 18, 2020

Comments

TiansHUo over 3 years

I am trying to convert strings into Inetaddress. I am not trying to resolve hostnames: the strings are ipv4 addresses. Does InetAddress.getByName(String host) work? Or do I have to manually parse it?
TiansHUo over 14 years

Thanks, I looked up the api, and missed that line.
Sebastian Hoffmann over 12 years

Whats when host is a pattern like 192.168.0.*? Will that work too? Regarding to Inet4Address doc there seems support for this.
Matthew Flaschen over 12 years

@Paranaix, no, it will throw a IllegalArgumentException with the message "invalid host wildcard specification"
Andre Holzner about 12 years

in particular, the documentation says: If a literal IP address is supplied, only the validity of the address format is checked. which I read as: 'if you specify a (dotted quad notation) IP address, no DNS lookup is performed'.
Matthew Flaschen about 12 years

This is part of Guava.
Raedwald about 11 years

The OP said "I am not trying to resolve hostnames"; if the input to getByName() is not a valid numeric IP address, but is a valid resolvable DNS name, the name will be resolved. That does not seem to be what the OP wants.
Matthew Flaschen about 11 years

@Raedwald, he also said "the strings are ipv4 addresses". If the input is known to be just IP addresses, this should work fine.
Craig Trader over 9 years

As of Java 7, this will throw an UnknownHostException; haven't checked earlier Javas, but I would expect an exception there as well.
silmeth over 7 years

It should be com.google.common.net.InetAddresses.forString (with InetAddresses with uppercase A). SO won’t allow me to correct that in your answer, as the edit has to be at least 6 characters. ;-) Anyway, thanks, was looking for it, and yet again Guava saves the day.
Marcono1234 almost 3 years

@CraigTrader, but if you look at the stack trace you will see that this is not actually a parsing exception, but Java tries to look this up as host name, which is somewhat worrying.
Craig Trader almost 3 years

Because 999.999.999.999 is NOT a valid IPv4 address, Java asks the system's name server to resolve it as a hostname. Since there is no valid DNS entry for that IP address, you'll get an UnknownHostException. If you try this with a valid IPv4 address, you'll get a valid InetAddress object.