Java 无需 DNS 查找即可将字符串转换为 InetAddress
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Convert a String to InetAddress without DNS lookup
提问by Bart Friederichs
I have a local IP address in dotted decimal notation in a String. I want to convert it to an InetAddressto feed it to Socket, but I need to do it without doing a DNS lookup (because this might cause lengthy timeouts).
我在String. 我想将其转换为 anInetAddress以将其提供给Socket，但我需要在不进行 DNS 查找的情况下执行此操作（因为这可能会导致长时间超时）。
Is there a ready method for that, or do I need to split the Stringand create the InetAddressfrom its bytes?
是否有现成的方法，或者我是否需要从其字节拆分String和创建InetAddress？
UpdateThe factory methods InetAddress.getByName()and InetAddress.getByAddress()don't seem to be a good fit, as they both also accept hostnames such as java.sun.com. There is no saying if they will try to contact a DNS server in their implementation.
更新工厂方法InetAddress.getByName()和InetAddress.getByAddress()似乎不太合适，因为它们都接受主机名，例如java.sun.com. 没有人说他们是否会在他们的实施中尝试联系 DNS 服务器。
采纳答案by Prabhakaran Ramaswamy
Do like this
这样做
InetAddress inetAddress = InetAddress.getByName("192.168.0.105");
If a literal IP address is supplied, only the validity of the address format is checked.
如果提供了文字 IP 地址，则仅检查地址格式的有效性。
java source code
java源代码
// if host is an IP address, we won't do further lookup if (Character.digit(host.charAt(0), 16) != -1 || (host.charAt(0) == ':')) { }
// if host is an IP address, we won't do further lookup if (Character.digit(host.charAt(0), 16) != -1 || (host.charAt(0) == ':')) { }
回答by Ali
You can do this by using the getByName method. for example:
您可以使用 getByName 方法执行此操作。例如：
InetAddress localhost = InetAddress.getByName("127.0.0.1")
As it is described on the java docs:
正如 java 文档中所描述的：
The host name can either be a machine name, such as "java.sun.com", or a textual representation of its IP address. If a literal IP address is supplied, only the validity of the address format is checked.
主机名可以是机器名称，例如“java.sun.com”，也可以是其 IP 地址的文本表示。如果提供了文字 IP 地址，则仅检查地址格式的有效性。
回答by Matt Ball
You can use Guava's InetAddresses#forString()which is specifically documented for your use case:
您可以使用专门针对您的用例记录的GuavaInetAddresses#forString()：
Returns the
InetAddresshaving the given string representation.
This deliberately avoids all nameservice lookups (e.g. no DNS).
返回
InetAddress具有给定字符串表示的 。
这特意避免了所有名称服务查找（例如，没有 DNS）。
(emphasis added)
（强调）
回答by Sean F
The open-source IPAddress Java librarywill validate all standard representations of IPv6 and IPv4 and will do so without DNS lookup. Disclaimer: I am the project manager of that library.
开源 IPAddress Java 库将验证 IPv6 和 IPv4 的所有标准表示，并且无需 DNS 查找。免责声明：我是那个图书馆的项目经理。
The following code will do what you are requesting:
以下代码将执行您的要求：
String str = "fe80:0:0:0:f06c:31b8:cd17:5a44";
try {
IPAddressString str = new IPAddressString(str);
IPAddress addr = str.toAddress();//throws if invalid, without a DNS lookup
InetAddress inetAddr = addr.toInetAddress();//convert valid address
//use address
} catch(AddressStringException e) {
//e.getMessage has validation error
}
