Java 一个奇怪的 UnknownHostException
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A strange UnknownHostException
提问by fuyou001
In a web project .
I see the log:
在一个网络项目中。
我看到日志：
hadoop.hbase.zookeeper.ZKConfig - java.net.UnknownHostException: example.com
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress.lookupAllHostAddr(InetAddress.java:850)
at java.net.InetAddress.getAddressFromNameService(InetAddress.java:1201)
at java.net.InetAddress.getAllByName0(InetAddress.java:1154)
at java.net.InetAddress.getAllByName(InetAddress.java:1084)
at java.net.InetAddress.getAllByName(InetAddress.java:1020)
at java.net.InetAddress.getByName(InetAddress.java:970)
but when I ping example.com, it's ok, I also telnet example.com 2181successfully!
I found the similar questionso I run the DomainResolutionTest in my Server java DomainResolutionTest example.com
but it's ok !
但是当我ping example.com 时，没关系，我也telnet example.com 2181成功！我发现了类似的问题，所以我在我的服务器java DomainResolutionTest example.com 中运行 DomainResolutionTest
但没关系！
env:
环境：
java -version
java version "1.6.0_25"
Java(TM) SE Runtime Environment (build 1.6.0_25-b06)
Java HotSpot(TM) 64-Bit Server VM (build 20.0-b11, mixed mode)
java version "1.6.0_25"
Java(TM) SE Runtime Environment (build 1.6.0_25-b06)
Java HotSpot(TM) 64-Bit Server VM (build 20.0-b11,混合模式)
os:Red Hat Enterprise Linux Server release 5.7
os:Red Hat Enterprise Linux Server release 5.7
I am curious why is Inet6AddressImpl,I think it may be Inet4AddressImpl
我很好奇为什么是Inet6AddressImpl，我觉得可能是Inet4AddressImpl
How to solve it?
What's the cause ?
如何解决？
是什么原因？
采纳答案by Hans Wurst
i have had the same exception and solved it by setting my hostname manually in /etc/hosts for the 'localhost' entry both.
我遇到了同样的异常，并通过在 /etc/hosts 中为“localhost”条目手动设置我的主机名来解决它。
127.0.0.1 localhost DL006285-linux
# special IPv6 addresses
::1 localhost ipv6-localhost ipv6-loopback DL006285-linux
回答by LarsK
If it is a dual stack (ipv6 + v4) Java prefers ipv6.
如果是双栈（ipv6 + v4）Java更喜欢ipv6。
You can force it to prefer ipv4, if your ipv6 is misconfigured somehow.
如果您的 ipv6 以某种方式错误配置，您可以强制它更喜欢 ipv4。
Set system property with: -Djava.net.preferIPv4Stack=true
设置系统属性：-Djava.net.preferIPv4Stack=true
soure: http://docs.oracle.com/javase/6/docs/technotes/guides/net/ipv6_guide/
来源：http://docs.oracle.com/javase/6/docs/technotes/guides/net/ipv6_guide/
回答by Laxminarayan
There may be problem in giving the subnet value to the program. I gave the subnet value by trimming it before passing to the program.
为程序提供子网值可能有问题。在传递给程序之前，我通过修剪它来给出子网值。
subnet = subnet.trim();
int timeout = 1500;
for(int i=1;i<254;i++)
{
try
{
String host = subnet +"."+i;
if (InetAddress.getByName(host).isReachable(timeout))
{
Check = Check+host+"\n";
System.out.println(host);
}
}
catch (UnknownHostException ex) {
Logger.getLogger(WiFi.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(WiFi.class.getName()).log(Level.SEVERE, null, ex);
