hi.

[root@bwg-vps lightsocks-java]# ls
client_start.sh LICENSE pom.xml README.md server_start.sh src
[root@bwg-vps lightsocks-java]# mvn package
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building lightsocks 0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
Downloading: http://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-compiler-plugin/3.1/maven-compiler-plugin-3.1.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.039s
[INFO] Finished at: Sat Apr 18 17:37:18 CST 2020
[INFO] Final Memory: 12M/56M
[INFO] ------------------------------------------------------------------------
[ERROR] Plugin org.apache.maven.plugins:maven-compiler-plugin:3.1 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-compiler-plugin:jar:3.1: Could not transfer artifact org.apache.maven.plugins:maven-compiler-plugin:pom:3.1 from/to central (http://repo.maven.apache.org/maven2): Failed to transfer file: http://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-compiler-plugin/3.1/maven-compiler-plugin-3.1.pom. Return code is: 501 , ReasonPhrase:HTTPS Required. -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginResolutionException
[root@bwg-vps lightsocks-java]#

how to fix it?