maven plugin should not use staged runtime

[vpa1977]

Bug Description

Maven plugin tries to use staged Java runtime instead of the one installed as the build package.
This causes a subsequent build failure due to runtime missing necessary modules to compile Java files.

To Reproduce

1. rockcraft pack
   Build succeeds
2. rockcraft pack
   Build fails

part yaml

name: maven-sample-chisel
version: 0.0.1
summary: Sample Maven-based chiselled rock
description: |
  This image is a sample maven application
  using openjdk-21-jre-headless slices

base: bare
build-base: [email protected]

run-user: _daemon_

platforms:
  amd64:

services:
  test:
    override: replace
    summary: Service summary
    command: /usr/bin/java -jar /jars/sample-0.0.1-SNAPSHOT.jar
    startup: enabled

parts:
  application:
    plugin: maven
    source: ./sample
    source-type: local
    build-packages:
      - maven
      - openjdk-21-jdk-headless

  runtime:
    plugin: nil
    source: https://github.com/vpa1977/chisel-releases
    source-type: git
    source-branch: 24.04-openjdk-21-jre-headless
    build-packages:
      - ca-certificates-java
    override-build: |
      chisel cut --release ./ --root ${CRAFT_PART_INSTALL} \
        base-files_base openjdk-21-jre-headless_security \
        openjdk-21-jre-headless_management \
        openjdk-21-jre-headless_jfr
      mkdir -p ${CRAFT_PART_INSTALL}/etc/ssl/certs/java/
      cp /etc/ssl/certs/java/cacerts ${CRAFT_PART_INSTALL}/etc/ssl/certs/java/cacerts
      java_bin=$(find ${CRAFT_PART_INSTALL} -name java -type f -executable)
      ln -s --relative $java_bin ${CRAFT_PART_INSTALL}/usr/bin/java

Relevant log output

2024-08-16 15:15:30.892 :: ## Plugin environment
2024-08-16 15:15:30.892 :: ## User environment
2024-08-16 15:15:30.892 :: 2024-08-16 15:15:29.753 plugin validation command: 'mvn --version'
2024-08-16 15:15:30.892 :: 2024-08-16 15:15:29.861 executed mvn --version with output �[1mApache Maven 3.8.7�[m
2024-08-16 15:15:30.892 :: Maven home: /usr/share/maven
2024-08-16 15:15:30.892 :: Java version: 21.0.4, vendor: Ubuntu, runtime: /root/stage/usr/lib/jvm/java-21-openjdk-amd64
2024-08-16 15:15:30.892 :: Default locale: en, platform encoding: UTF-8
2024-08-16 15:15:30.892 :: OS name: "linux", version: "6.8.0-40-generic", arch: "amd64", family: "unix"
2024-08-16 15:15:30.892 :: 2024-08-16 15:15:29.861 Executing PosixPath('/root/parts/application/run/build.sh')

[vpa1977]

See #813 for the sample project.

[lengau]

I'm not sure we can do this without breaking backwards compatibility, but maybe we can provide an option about staging a JRE (defaulting to True)?

@cmatsuoka what do you think?

[vpa1977]

The issue with the staged runtime is that the error message from the build is misleading - release X is not supported. and there is no way to make maven use the desired JDK.
It would be nice to have java_home property to point it to the right Java that should default to build-package JDK if present.

[vpa1977]

The root cause is stage path being prepended to the PATH:

/root/stage/usr/bin:/snap/rockcraft/x1/libexec/rockcraft:/snap/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

This forces Java plugins to use staged runtime.

[tigarmo]

The stage dir is always prepended to the PATH, yes. That's typically how one can use a custom version of build tools. It's too late to change this now but we can discuss alternatives for 26.04.

What's really interesting to me, though, is that Maven is picking up the staged Java even though it's just the runtime, and not a full JDK. That looks like a bug we might be able to fix. @vpa1977 do you know if there's any way to control how Maven finds the Java to use?

[vpa1977]

What's really interesting to me, though, is that Maven is picking up the staged Java even though it's just the runtime, and not a full JDK. That looks like a bug we might be able to fix. @vpa1977 do you know if there's any way to control how Maven finds the Java to use?

Maven checks JAVA_HOME and then the search path.
Note: this is not Maven-specific. Gradle will use the search path and ignore JAVA_HOME (kind of).

[tigarmo]

so in this case would it be enough to set JAVA_HOME in the part's build-environment?

[vpa1977]

so in this case would it be enough to set JAVA_HOME in the part's build-environment?

This would be sufficient for maven plugin