Why maven-resources-plugin ignores my charset encoding setting?

Question

I have a java artifact dual-built for both linux & IBM mainframe, all the dependent shell scripts (in /sbin dir) are initially written in ASCII but are copied to another directory (in /sbin-ebcdic). So I configure the maven-resources-plugin to do it for me:

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-resources-plugin</artifactId>
            <version>3.0.1</version>
            <executions>
                <execution>
                    <id>copy-sbin</id>
                    <phase>process-resources</phase>
                    <goals>
                        <goal>copy-resources</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>${project.basedir}/sbin-ebcdic</outputDirectory>
                        <resources>
                            <resource>
                                <directory>${project.basedir}/sbin</directory>
                            </resource>
                        </resources>
                        <encoding>IBM037</encoding>
                    </configuration>
                </execution>
            </executions>
        </plugin>

While it does copy the entire directory, all files in them are still in UTF-8 encoding, as if my:

<encoding>IBM037</encoding>

setting doesn't exist. Why the maven-resources-plugin doesn't function as intended? Is it a bug?

Answer 1

If you read the documentation carefully of resources:copy-resources, it says this about <encoding>:

The character encoding scheme to be applied when filtering resources.

If you are not doing filtering, the resources plugin will simply do a byte-for-byte copy. If you want it to transform the resources using the specified encoding, you need to enable filtering, even though you aren't using property interpolation.

EDITED:

I just confirmed it. The specified encoding is used both when reading and writing the file, which seems counter-intuitive. If you take a look at line 144 in DefaultMavenFileFilter.java in the dependency chain of maven-resources-plugin:3.0.1:

143     fileReader = getFileReader( encoding, from );
144     fileWriter = getFileWriter( encoding, to );
145     Reader src = readerFilter.filter( fileReader, true, wrappers );
146
147     IOUtil.copy( src, fileWriter );

When I changed the encoding of getFileWriter() to UTF-8 while debugging, it worked as one would expect.

Basically, you have a couple of options:

• Write your own plugin. It's not that hard for this type of use-case.
• File an improvement ticket (I am thinking about doing this myself if you don't) with the maintainers to introduce an <outputEncoding> configuration parameter.
• If you're in a pinch, create your own fork of the plugin. Obviously it would be great if you could contribute your work to the main development stream.