JDK discovery mechanism now working as expected

[4r73m190r0s]

Affected version

3.2.0

Bug description

Executing mvn org.apache.maven.plugins:maven-toolchains-plugin:3.2.0:display-discovered-jdk-toolchains works, and returns all JDKs installed on my machine, but I don't know how to cinfigure Maven to use Java 8 for project runtime.

This auto discovery mechanism should work without ~/.m2/toolchains.xml file per documentation.

My goal is to run project with Java 8.

My 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.7.18</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.username.mock</groupId>
	<artifactId>webserver</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>webserver</name>
	<description>Demo project for Spring Boot</description>
	<url/>
	<licenses>
		<license/>
	</licenses>
	<developers>
		<developer/>
	</developers>
	<scm>
		<connection/>
		<developerConnection/>
		<tag/>
		<url/>
	</scm>
	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-toolchains-plugin</artifactId>
        <version>3.2.0</version>
        <executions>
          <execution>
            <goals>
              <goal>select-jdk-toolchain</goal>
            </goals>
            <configuration>
              <discoverToolchains>true</discoverToolchains>
              <runtimeVersion>8</runtimeVersion>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
	</build>
</project>

Error I get with mvn spring-boot:run:

[INFO] Found 5 possible jdks: [/usr/lib/jvm/java-21-openjdk, /usr/lib/jvm/java-11-openjdk, /usr/lib/jvm/java-24-openjdk, /usr/lib/jvm/java-17-openjdk, /usr/lib/jvm/java-8-openjdk]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.884 s
[INFO] Finished at: 2025-06-18T13:41:51+02:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-toolchains-plugin:3.2.0:select-jdk-toolchain (default) on project webserver: Cannot find matching toolchain definitions for the following toolchain types:{runtime.version=8}
[ERROR] Define the required toolchains in your ~/.m2/toolchains.xml file.
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

[jafarre-bi]

I don't think the runtime version is what you really want.
I suggest replacing the <runtimeVersion/> config parameter with <version>[8,9)</version>, or simply defining the property <toolchain.jdk.version>[8,9)</toolchain.jdk.version> and removing the entire config section.