Upgrading Maven plugins to Java 11

Question

I am upgrading my Maven-built, Java 8 app to Java 11. In my POM I specify:

<properties>
  <java.version>1.11</java.version>
  <maven.compiler.source>${java.version}</maven.compiler.source>
  <maven.compiler.target>${java.version}</maven.compiler.target>
</properties>

When I go to build my app using my normal Maven build invocation:

mvn verify -Plocal -Dspring-boot.run.jvmArguments="-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=5005"

I get:

[INFO] Scanning for projects...
[INFO] 
[INFO] -----------------------< example.com:myapp-svc >------------------------
[INFO] Building myapp-svc 1
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-checkstyle-plugin:3.1.2:check (validate) @ myapp-svc ---
[WARNING] Old version of checkstyle detected. Consider updating to >= v8.30
[WARNING] For more information see: https://maven.apache.org/plugins/maven-checkstyle-plugin/examples/upgrading-checkstyle.html
[INFO] Starting audit...
Audit done.
[INFO] You have 0 Checkstyle violations.
[INFO] 
[INFO] --- jacoco-maven-plugin:0.8.7:prepare-agent (default) @ myapp-svc ---
[INFO] argLine set to -javaagent:/Users/myuser/.m2/repository/org/jacoco/org.jacoco.agent/0.8.7/org.jacoco.agent-0.8.7-runtime.jar=destfile=/Users/myuser/workspace/myapp-svc/target/jacoco.exec
[INFO] 
[INFO] --- maven-resources-plugin:3.1.0:resources (default-resources) @ myapp-svc ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 6 resources
[INFO] Copying 154 resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ myapp-svc ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 456 source files to /Users/myuser/workspace/myapp-svc/target/classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  3.076 s
[INFO] Finished at: 2021-11-12T12:52:52-05:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile (default-compile) on project myapp-svc: Fatal error compiling: error: invalid target release: 1.11 -> [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/MojoExecutionException

So it looks like the maven-compiler-plugin:3.8.1 plugin is incompatible with Java 11. The thing is, I don't directly specify that plugin anywhere in my POM. So something, somewhere is pulling it and using it, and my guess is that I have to update whatever that thing is so that it pulls in a version of the maven-compiler-plugin that is compatible with Java 11.

So how can I tell what's pulling it in and using it? Or if thats not what's happening, what is and how do I fix it?

Answer 1

tl;dr

Drop the 1. prefix.

<java.version>11</java.version>

Details

New versioning scheme in Java 9+

As of Java 9 and later, the Java version numbering scheme was altered to drop the never-changing 1.*.

For official documentation and explanation, see JEP 223: New Version-String Scheme, section Dropping the initial 1 element from version numbers.

To quote JEP 223:

This proposal drops the initial 1 element from JDK version numbers. That is, it suggests that the first release of JDK 9 will have the version number 9.0.0 rather than 1.9.0.0.

After nearly twenty years it's clear that the second element of the current version-number scheme is the JDK's de facto $MAJOR version number.

Therefore your POM should use:

<java.version>11</java.version>

---

<maven.compiler.release>

By the way, if you update the other parts of your POM related to the compiler, building, and testing to their latest versions, you can replace the pair of elements <maven.compiler.source> and <maven.compiler.target> to simply this one element: <maven.compiler.release>.

So your snippet:

<properties>
  <java.version>1.11</java.version>
  <maven.compiler.source>${java.version}</maven.compiler.source>
  <maven.compiler.target>${java.version}</maven.compiler.target>
</properties>

… becomes this:

<properties>
  <java.version>11</java.version>
  <maven.compiler.release>${java.version}</maven.compiler.release>
</properties>

And in my own work, I do not even have a java.version element at all. I use simply this snippet, to specify UTF-8 as the charactering encoding, and Java 17 as the compiling and building version.

  <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <maven.compiler.release>17</maven.compiler.release>
  </properties>

With UTF-8 becoming the new Java 18 default across platforms (see JEP 400: UTF-8 by Default), in the future I may be able to drop that first element, <project.build.sourceEncoding>.

  <properties>
      <maven.compiler.release>17</maven.compiler.release>
  </properties>

Here is my modified version of the Apache Maven Quickstart Archetype, as a full example.

<?xml version="1.0" encoding="UTF-8"?>

<!-- Modified by Basil Bourque as of 2021-11 to use the latest versions. -->
<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>

    <groupId>work.basil.example</groupId>
    <artifactId>Quickie</artifactId>
    <version>1.0-SNAPSHOT</version>

    <name>Quickie</name>
    <url>http://www.basil.work</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.release>17</maven.compiler.release>
    </properties>

    <dependencies>

        <!-- https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter -->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>5.8.1</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>
        <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
            <plugins>
                <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
                <plugin>
                    <artifactId>maven-clean-plugin</artifactId>
                    <version>3.1.0</version>
                </plugin>
                <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
                <plugin>
                    <artifactId>maven-resources-plugin</artifactId>
                    <version>3.2.0</version>
                </plugin>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.8.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>3.0.0-M5</version>
                </plugin>
                <plugin>
                    <artifactId>maven-jar-plugin</artifactId>
                    <version>3.2.0</version>
                </plugin>
                <plugin>
                    <artifactId>maven-install-plugin</artifactId>
                    <version>3.0.0-M1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-deploy-plugin</artifactId>
                    <version>3.0.0-M1</version>
                </plugin>
                <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
                <plugin>
                    <artifactId>maven-site-plugin</artifactId>
                    <version>3.9.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-project-info-reports-plugin</artifactId>
                    <version>3.1.2</version>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

Answer 2

Replace <java.version>1.11</java.version> by <java.version>11</java.version>