Hello Maven Users,
Some context: We are developing a webapp which utilizes React for our UI
component. It is an known/open issue that React applications need to
know their deployment location when built, because resource paths are
embedded into the build output.
See: https://github.com/facebook/create-react-app/issues/2353
See:
https://web.archive.org/web/20190729194150/https://github.com/facebook/create-react-app/issues/2353
We've worked around the issue by setting our deployment path to some
constant like PUBLIC_URL_REPLACE_ME and then using a Response filter to
substitute the the value of request.getContextPath() of the relevant
resources at run time.
We'd like to instead substitute JSP like "<%=request.getContextPath()%>"
at build time instead of using a Response filter at run time. However,
we also need to place a JSP page directive at the beginning of our
resources to correct Content-Type and either disable or escape EL and
such, so this isn't as simple as configuring React to use "@PUBLIC_URL@"
and substituting with the built-in Maven Resources filtering.
I understand maven-resources-plugin supports the usage of one or more
custom resource filters,
See:
https://maven.apache.org/plugins/maven-resources-plugin/examples/custom-resource-filters.html
See:
https://web.archive.org/web/20190729180428/https://maven.apache.org/plugins/maven-resources-plugin/examples/custom-resource-filters.html
but it is not clear to me how this is intended to work, or if its design
even accomplishes the developers' intent.
For example, I would expect to use the Wrapper design pattern to wrap an
InputStream or OutputStream as it is used to copy/filter the file
contents to the destination during copy-resources. While this design
pattern is supported by the involved MavenFileFilter [1], there is no
code path from a custom MavenResourcesFiltering [2] implementation to
add a FilterWrapper to the list [3].
I would expect to use mavenResourcesExecution.addFilterWrapper() in
filterResources() of my custom MavenResourcesFiltering implementation,
but custom filters are executed *after* DefaultMavenResourcesFiltering [4].
While the added FilterWrapper would be available to the custom
MavenResourcesFiltering implementations, one of the implementations
would need to *duplicate* the logic of DefaultMavenResourcesFiltering
and do a *second* copy of all of the resources in order to correct the
lack of custom FilterWrappers when DefaultMavenResourcesFiltering was
executed. I do not think this approach is sensible, or the intention of
the custom resources filters support.
Another approach I've seen involves extending
DefaultMavenResourcesFiltering or DefaultMavenFileFilter with another
class that takes on the same Plexus hint="default" [5] [6], but this
approach doesn't even utilize the custom resources filter support
(you're basically overriding an internal Maven component when doing
this), nor can it compound unrelated filters.
In all cases, there does not appear to be a way configure custom
resources filters per execution or per resource directory defined in the
POM, and information about the resource, like file name, are not passed
to FilterWrappers (which complicates my ability to correctly set
Content-Type in the JSP page directive).
So... are these issues just untested oversights and the existing custom
resources filters support is useless, or am I misunderstanding how they
are *supposed* to be utilized?
Where do we (either our project, or Maven) go from here? Should this be
brought to Maven Developer List for collaboration on improving the design?
Thank you,
Kyle Marek
[1]:
See:
https://maven.apache.org/shared/maven-filtering/apidocs/org/apache/maven/shared/filtering/MavenFileFilter.html#copyFile(java.io.File,%20java.io.File,%20boolean,%20java.util.List,%20java.lang.String)
See:
https://web.archive.org/web/20190729191655/https://maven.apache.org/shared/maven-filtering/apidocs/org/apache/maven/shared/filtering/MavenFileFilter.html#copyFile(java.io.File,%20java.io.File,%20boolean,%20java.util.List,%20java.lang.String)
[2]:
See:
https://maven.apache.org/shared/maven-filtering/apidocs/org/apache/maven/shared/filtering/MavenResourcesFiltering.html
See:
https://web.archive.org/web/20190729191210/https://maven.apache.org/shared/maven-filtering/apidocs/org/apache/maven/shared/filtering/MavenResourcesFiltering.html
[3]:
See:
https://github.com/apache/maven-filtering/blob/0f4f3eda5b59a303f9657f1e38bff8e54956d377/src/main/java/org/apache/maven/shared/filtering/DefaultMavenResourcesFiltering.java#L233-L236
See:
https://web.archive.org/web/20190729191319/https://github.com/apache/maven-filtering/blob/0f4f3eda5b59a303f9657f1e38bff8e54956d377/src/main/java/org/apache/maven/shared/filtering/DefaultMavenResourcesFiltering.java#L233-L236
[4]:
See:
https://github.com/apache/maven-resources-plugin/blob/maven-resources-plugin-3.1.0/src/main/java/org/apache/maven/plugins/resources/ResourcesMojo.java#L345-L347
See:
https://web.archive.org/web/20190729191943/https://github.com/apache/maven-resources-plugin/blob/maven-resources-plugin-3.1.0/src/main/java/org/apache/maven/plugins/resources/ResourcesMojo.java#L345-L347
[5]:
See:
https://stackoverflow.com/questions/30798935/externalized-filters-when-building-a-maven-project/32184390#32184390
See:
https://web.archive.org/web/20190729192250/https://stackoverflow.com/questions/30798935/externalized-filters-when-building-a-maven-project/32184390#32184390
[6]:
See:
https://stackoverflow.com/questions/40216611/custom-mavenresourcesfiltering-hard-to-implement/40220837#40220837
See:
https://web.archive.org/web/20190729192054/https://stackoverflow.com/questions/40216611/custom-mavenresourcesfiltering-hard-to-implement/40220837#40220837
See:
https://jeremylong.github.io/velocity-whitespace-resource-filter/xref/org/owasp/maven/tools/VelocityWhitespaceFilter.html
See:
https://web.archive.org/web/20190729192136/https://jeremylong.github.io/velocity-whitespace-resource-filter/xref/org/owasp/maven/tools/VelocityWhitespaceFilter.html
See:
https://jeremylong.github.io/velocity-whitespace-resource-filter/xref/org/owasp/maven/tools/VelocityWhitespaceFilterWrapper.html
See:
https://web.archive.org/web/20190729192214/https://jeremylong.github.io/velocity-whitespace-resource-filter/xref/org/owasp/maven/tools/VelocityWhitespaceFilterWrapper.html
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