plugin version resolved twice, second time wrong version resolved

Question

I'm trying to build JIRA 6.0.7 from source

https://confluence.atlassian.com/jira064/building-jira-from-source-720411927.html

It had build issues with JDK-8 so I had to use JDK-7. One artifact downloads latest plugin version (although explicit version is defined in pom.xml) and fails, because of class file version.

Here's the output of mvn -X package:

[INFO] Scanning for projects...
[DEBUG] com.atlassian.maven.plugins:maven-jira-plugin:jar:4.1.5:
[DEBUG]    com.atlassian.maven.archetypes:jira-plugin-archetype:jar:4.1.5:runtime
[DEBUG]    com.atlassian.maven.plugins:maven-amps-plugin:jar:4.1.5:compile
...
[DEBUG]   Included: com.atlassian.maven.plugins:maven-amps-plugin:jar:4.1.5
...
[DEBUG] Resolving plugin version for com.atlassian.maven.plugins:maven-amps-plugin
[DEBUG] Could not find metadata com.atlassian.maven.plugins:maven-amps-plugin/maven-metadata.xml in local (C:\m2repo)
[DEBUG] Skipped remote update check for com.atlassian.maven.plugins:maven-amps-plugin/maven-metadata.xml, locally cached metadata up-to-date.
[DEBUG] Skipped remote update check for com.atlassian.maven.plugins:maven-amps-plugin/maven-metadata.xml, locally cached metadata up-to-date.
[DEBUG] Resolved plugin version for com.atlassian.maven.plugins:maven-amps-plugin to 6.2.6 from repository atlassian-proxy (https://m2proxy.atlassian.com/repository/public, releases+snapshots)
...
Caused by: java.lang.UnsupportedClassVersionError: com/atlassian/maven/plugins/amps/osgi/ValidateTestManifestMojo : Unsupported major.minor version 52.0

Here's simplified pom to reproduce the problem:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>

    <groupId>bar</groupId>
    <artifactId>foo</artifactId>
    <version>1.1.7</version>
    <packaging>atlassian-plugin</packaging>
    <name>foo</name>
    <description>foo</description>


<dependencies>
</dependencies>

    <repositories>
        <repository>
            <id>atlassian-proxy</id>
            <name>Atlassian Maven 2 Proxy</name>
            <url>https://m2proxy.atlassian.com/repository/public</url>
        </repository>
        <repository>
            <id>atlassian-contrib</id>
            <name>Atlassian Contrib Repository</name>
            <url>https://m2proxy.atlassian.com/contrib</url>
        </repository>
    </repositories>
    <pluginRepositories>
    <pluginRepository>
            <id>atlassian-proxy</id>
            <name>Atlassian Maven 2 Proxy</name>
            <url>https://m2proxy.atlassian.com/repository/public</url>
        </pluginRepository>
    </pluginRepositories>

    <build>
        <plugins>
            <plugin>
                <groupId>com.atlassian.maven.plugins</groupId>
                <artifactId>maven-jira-plugin</artifactId>
                <version>4.1.5</version>
                <extensions>true</extensions>
            </plugin>
        </plugins>
    </build>

</project>

Note

maven-amps-plugin-4.1.5.jar is built for java 6:

C:\>javap -v -classpath maven-amps-plugin-4.1.5.jar com.atlassian.maven.plugins.amps.osgi.ValidateTestManifestMojo | find "major version"
  major version: 50

Note2

I'm so desperate, I'm now debugging maven code. https://maven.apache.org/ref/3.3.1/xref/org/apache/maven/plugin/version/internal/DefaultPluginVersionResolver.html#L90

Before falling back to resolveFromRepository() it tries to resolveFromProject(), but fails, because request.pom == null. Why?

project.getBuildPlugins() returns (among many) maven-amps-plugin with version == null. Why?

project.getBuildPlugins().get(0)
    artifactId  "maven-jira-plugin" (id=489)    
    version "4.1.5" (id=498)    

project.getBuildPlugins().get(5)
    artifactId  "maven-amps-plugin" (id=402)    
    version null    

Initially, a Plugin object is created with correct version while parsing com/atlassian/amps/standalone/4.1.5/standalone-4.1.5.pom, but then another instance created in DefaultLifecyclePluginAnalyzer.parseLifecyclePhaseDefinitions(). I guess it's caused by <packaging>atlassian-plugin</packaging>

Answer 1

It appears that maven-amps-plugin 4.1.5, a dependency of maven-jira-plugin is built using JDK 8. I tried to experiment with the versions I could get, hopefully a previous version. Curiously, Maven Central has a 5.0.18 from 2015, so I mused with it, and ended up with a problem with the Oracle driver, which is OK (since Oracle drivers, if I'm not mistaken are not stored on Central). Your local repository might have it, and this snippet could help you. So even if it's unlikely the proper solution to your problem, just in case.

        <plugin>
            <groupId>com.atlassian.maven.plugins</groupId>
            <artifactId>maven-jira-plugin</artifactId>
            <version>4.1.5</version>
            <extensions>true</extensions>
            <dependencies>
                <dependency>
                    <groupId>com.atlassian.maven.plugins</groupId>
                    <artifactId>maven-amps-plugin</artifactId>
                    <version>5.0.18</version>
                </dependency>
            </dependencies>
        </plugin>