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https://issues.apache.org/jira/browse/LANG-1472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16906019#comment-16906019
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Silence Tai commented on LANG-1472:
-----------------------------------
[~VioletKiss]
The *getHostName* method works on the non-Widnwos platform depending on the
*HOSTNAME* environment variable, but there is no definition in your current
environment variable, so getting {color:#FF0000}null{color} is normal.
{code:java}
/**
* Gets the host name from an environment variable.
*
* <p>
* If you want to know what the network stack says is the host name, you
should use {@code InetAddress.getLocalHost().getHostName()}.
* </p>
*
* @return the host name.
* @since 3.6
*/
public static String getHostName() {
return IS_OS_WINDOWS ? System.getenv("COMPUTERNAME") :
System.getenv("HOSTNAME");
}
{code}
You can see in the program through the *System.getenv()* method that the
environment name of the *HOSTNAME* is not registered in the program instance.
> SystemUtils.getHostName()获取系统hostname为null
> ------------------------------------------
>
> Key: LANG-1472
> URL: https://issues.apache.org/jira/browse/LANG-1472
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.*
> Affects Versions: 3.9
> Environment: * 操作系统：阿里云提供的Ubuntu 16.04
> root@iZwz99ibpdra8w3j3jcbw7Z:~# hostname
> iZwz99ibpdra8w3j3jcbw7Z
> root@iZwz99ibpdra8w3j3jcbw7Z:~# echo $HOSTNAME
> iZwz99ibpdra8w3j3jcbw7Z
> * 语言：Java 8
> root@iZwz99ibpdra8w3j3jcbw7Z:~# java -version
> java version "1.8.0_191"
> Java(TM) SE Runtime Environment (build 1.8.0_191-b12)
> Java HotSpot(TM) 64-Bit Server VM (build 25.191-b12, mixed mode)
> Reporter: wangrubao
> Priority: Critical
> Attachments: SnowflakeIdWorker.java, error.png, pom.xml
>
>
> SpringBoot 项目获取系统 hostname 为 null 导致 java.lang.NullPointerException 。
> 部分代码：
> private static Long getDataCenterId(){
> int[] ints = StringUtils.toCodePoints(SystemUtils.getHostName());
> int sums = 0;
> for (int i: ints) {
> sums += i;
> }
> return (long)(sums % 32);
> }
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