When using the apache antrun plugin -- more formally known as maven-antrun-plugin -- it's possible (since 2010) to expose antrun properties to Maven using the configuration exportAntProperties set to true. This works great for "inlined" <target> code, which is what most online examples I've found use.
However, according to the antrun main project page, it's encouraged to use an external build.xml file instead of "inline" code, quoting:
"[...] it's encouraged to move all your Ant tasks to a
build.xmlfile and just call it from the POM using Ant's<ant/>task."
... however, it seems much harder to access properties set through the build.xml file.
How do you access/retrieve a property from within a build.xml file from a Maven project? This works fine for inlined code, but external files are proving much more difficult.
Code:
pom.xml:
<?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/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<name>Antrun Tests</name>
<description>To test inline antrun tasks versus external antrun tasks</description>
<groupId>org.example</groupId>
<artifactId>antrun</artifactId>
<version>1.0.0</version>
<build>
<defaultGoal>validate</defaultGoal>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-antrun-plugin</artifactId>
<version>1.8</version>
<executions>
<!-- Inline -->
<execution>
<id>inline-ant</id>
<goals><goal>run</goal></goals>
<phase>validate</phase>
<configuration>
<target name="inline-ant">
<property name="inline.ant" value="PASS"/>
<echo level="info">Ant scope:</echo>
<echo level="info">[inline.ant]: (set to: ${inline.ant})</echo>
</target>
<exportAntProperties>true</exportAntProperties>
</configuration>
</execution>
<!-- External -->
<execution>
<id>external-ant</id>
<goals><goal>run</goal></goals>
<phase>validate</phase>
<configuration>
<target name="external-ant">
<ant antfile="build.xml"/>
</target>
<exportAntProperties>true</exportAntProperties>
</configuration>
</execution>
<!-- Echo results -->
<execution>
<id>results</id>
<goals><goal>run</goal></goals>
<phase>validate</phase>
<configuration>
<target name="results">
<!--
Note: This conditional logic is superfluous!
Ant can NOT set set a variable if it's already
set! However, since Maven's default behavior allows
this, I'm adding a clear, unnecessary guard as to
not confuse causal onlookers. <3
-->
<!-- Set to failed if not set -->
<condition property="inline.ant" value="FAILED">
<not><isset property="inline.ant"/></not>
</condition>
<condition property="external.ant" value="FAILED">
<not><isset property="external.ant"/></not>
</condition>
<!-- Echo to console -->
<echo level="info">Maven scope:</echo>
<echo level="info">[inline.ant]: ${inline.ant}</echo>
<echo level="info">[external.ant]: ${external.ant}</echo>
</target>
<exportAntProperties>true</exportAntProperties>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
... and relevant build.xml:
<project default="external-ant">
<target name="external-ant">
<property name="external.ant" value="PASS"/>
<echo level="info">Ant scope:</echo>
<echo level="info">[external.ant]: (set to: ${external.ant})</echo>
</target>
</project>
Edit: I think this may actually be a side-effect of ant's <ant antfile="..."> task, and the antrun plugin is collateral damage to it.
For example, If I had access to <import file="..."/>, I believe it would work, but ant requires imports at the <project> level and antrun doesn't allow anything higher-level than the <target> level (<target> must be a child of <project>).
For example, even if I echo in the same exact ant target, I still can't see the properties, suggesting it a nuance of forcing people to use <ant antfile="..."> to begin with, conflicting with expected behavior, and conflicting with the "encouraged" use from antrun's documentation.
