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https://issues.apache.org/jira/browse/MTOOLCHAINS-44?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17916469#comment-17916469
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dennis lucero commented on MTOOLCHAINS-44:
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I noticed the toolchains plugin now has a [JDK discovery
mechanism|https://maven.apache.org/plugins/maven-toolchains-plugin/toolchains/jdk-discovery.html].
However it doesn’t work as I would expect after reading the documentation.
* I don’t see any effect of {{{}<goal>select-jdk-toolchain</goal>{}}}. I
thought it would set some internal state so the following
{{<goal>toolchain</goal>}} would work, but that goal fails although {{mvn
org.apache.maven.plugins:maven-toolchains-plugin:3.2.0:display-discovered-jdk-toolchains}}
finds the JDK matching the required version in the toolchains plugin
configuration section (using the {{maven:3-eclipse-temurin-17-alpine}} Docker
image).
* Running {{mvn
org.apache.maven.plugins:maven-toolchains-plugin:3.2.0:generate-jdk-toolchains-xml}}
generates {{~/.m2/discovered-jdk-toolchains-cache.xml}} which does not seem to
have any effect. However it works when renaming it to {{toolchains.xml}}.
> Use default JDK if it matches the request and no other toolchain is defined
> ---------------------------------------------------------------------------
>
> Key: MTOOLCHAINS-44
> URL: https://issues.apache.org/jira/browse/MTOOLCHAINS-44
> Project: Maven Toolchains Plugin
> Issue Type: Improvement
> Affects Versions: 3.1.0
> Reporter: dennis lucero
> Priority: Major
>
> Currently it is needed to have the toolchains defined in the toolchains.xml
> file. The [Maven Docker images|https://hub.docker.com/_/maven] do not
> [include a useful toolchains
> file|https://github.com/carlossg/docker-maven/issues/303]. But since it’s
> possible to [derive a usable toolchain from the system
> properties|https://github.com/carlossg/docker-maven/issues/303#issuecomment-1310895631],
> it should not be required to store that information in the toolchains.xml
> file. Instead, Maven should check if the toolchain request could be fulfilled
> by the JDK running Maven.
> I’m not sure if it’s reasonable to do this in all cases or only if the
> toolchains file does not contain any toolchain. For example, if the
> toolchains file only contains a Java 16 toolchain and the project requires
> Java 17 (exactly, not 17 or later) and Maven is run with Java 17, it would be
> possible to build the project (with Java 17), but probably not a good idea
> since it will fail when the Java installation Maven is running on is updated
> to version 18.
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