I'm familiar with how to set Maven to use a specific encoding, for example here. However, I want to know which encoding's Maven will support.
All I can find from Maven is a vague quote referring to mvn-resources-plugin that gives examples, but not an exhaustive list:
A character encoding scheme such as ASCII, UTF-8 or UTF-16 can be chosen to be used for the reading and writing of files.
To define 'supported', say I have a pom.xml that contains the following:
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<version>3.2.0</version>
<configuration>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
If I run the above with UTF-8, then everything runs fine, and this is considered supported. Specifically on mvn-resources-plugin I see:
[INFO] --- maven-resources-plugin:3.2.0:resources (default-resources) @ maven-encoding ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Using 'UTF-8' encoding to copy filtered properties files.
However, if I run Maven with an encoding of unknown, it is unsupported, as I get errors, for example:
[INFO] Building maven-encoding 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] --- maven-resources-plugin:3.2.0:resources (default-resources) @ maven-encoding ---
[INFO] Using 'unknown' encoding to copy filtered resources.
[INFO] Using 'unknown' encoding to copy filtered properties files.
[INFO] skip non existing resourceDirectory <directory>
[INFO]
[INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ maven-encoding ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 2 source files to <directory>
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4.396 s
[INFO] Finished at: 2022-09-17T21:05:30+01:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile (default-compile) on project maven-encoding: Fatal error compiling: unknown -> [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/MojoExecutionException
I note that it is interesting that it appears that mvn-resources-plugin does not seem to give me any errors, but mvn-compiler-plugin does.
I care about this because I need to be able to advise someone for which encodings that Maven would run. I have of course advised them that it would be sensible to ensure that their environment copes with UTF-8, or at least a common encoding, but I have been told that this is not guaranteed.
In answering the above, I anticipate we will also find out the answers to the following corollary questions:
Does the answer change on a plugin-by-plugin basis? (for example, mvn-compiler-plugin has a separate encoding setting to mvn-resources-plugin)
Is the set of supported encodings defined by Maven, or by the operating system that Maven is running on (or otherwise)?
