在 Java 中检查字符串是主机名还是 IP 地址

Question

I want to check if a string is a hostname or an ip-address in Java. Is there an API to do it or must I write a parser myself?

The problem is complex because there are IPv4 addresses, short and long IPv6 addresses, short hostnames and FQDN host names.

Answer 1

There doesn't appear to be an API, but writing such function doesn't seem to be very difficult. You can check the following conditions in your code:

1. If sourceStr contains ":" but no "." -> IPv6
2. If sourceStr.matches("^.[0-9]{1,3}/..[0-9]{1,3}/..[0-9]{1,3}/..[0-9]{1,3}") == true) -> IPv4
3. If sourceStr contains "." -> FQDN host name
4. Otherwise it must be a short hostname

Answer 2

To expand @MrGomez 's answer, Use InetAddresses to validate IP Addresses and InternetDomainName to validate hostnames (FQDN).

Example:

public static boolean validate(final String hostname) {
        return InetAddresses.isUriInetAddress(hostname) || InternetDomainName.isValid(hostname);
    }

Answer 3

在 JDK API 中不可能，但您可以在google guava 中使用InetAddresses.forString当参数不是 IP 字符串文字时抛出异常。

Answer 4

While you could theoretically write rules to handle these cases yourself, using the usual cadre of RFCs , I'd instead look at the entirety of this class in Google Guava , especially the corner cases, such as how it resolves the embedding of 4-in-6 addresses.

As for determining if you have a FQDN, see if coercion to IP address fails, then try to resolve it against DNS. Anything else should, given your input cases, be a hostname or local resolution that isn't fully qualified.

Answer 5

The IPAddress Java library will do it. The javadoc is available at the link. Disclaimer: I am the project manager.

static void check(HostName host) {
    try {
        host.validate();
        if(host.isAddress()) {
            System.out.println("address: " + host.asAddress());
        } else {
            System.out.println("host name: " + host);
        }
    } catch(HostNameException e) {
        System.out.println(e.getMessage());
    }
}

public static void main(String[] args) {
    HostName host = new HostName("1.2.3.4");
    check(host);
    host = new HostName("1.2.a.4");
    check(host);
    host = new HostName("::1");
    check(host);
    host = new HostName("[::1]");
    check(host);
    host = new HostName("1.2.?.4");
    check(host);  
}

Output:

address: 1.2.3.4
host name: 1.2.a.4
address: ::1
address: ::1
1.2.?.4 Host error: invalid character at index 4

Answer 6

import sun.net.util.IPAddressUtil
IPAddressUtil.isIPv4LiteralAddress(addr)
IPAddressUtil.isIPv6LiteralAddress(addr)