Maven Toolchains now work with a new Maven Compiler Plugin version. Updated the documentation and added an example configuration for Java16.

johanjanssen · johanjanssen · commit f22dead5de34 · 2022-03-15T10:25:59.000+01:00
diff --git a/README.md b/README.md
@@ -517,8 +517,6 @@ docker build -t javaupgrades -f ..\DockerfileJava8 --build-arg DISABLE_CACHE="%d
 
 
 ## Maven Toolchains
-**Please read until the end, for now I don't recommend the Maven toolchains as there appears to be a bug.**
-
 Maven Toolchains can be used to configure the JDK's present on your machine and then select one to use in the `pom.xml` of the project.
 
 First create a `toolchains.xml` located in *${user.home}/.m2/*
@@ -566,7 +564,6 @@ First create a `toolchains.xml` located in *${user.home}/.m2/*
 ```
 
 Then in the `pom.xml` configure which JDK from the toolchains.xml you want to use:
-
 ```xml
 <build>
     <plugins>
@@ -593,18 +590,18 @@ Then in the `pom.xml` configure which JDK from the toolchains.xml you want to us
 </build>
 ```
 
-Unfortunately currently there seems to be a bug as building the project with the toolchain gives:
+Make sure to update the Maven Compiler Plugin. When using an older version, combined with the Toolchains Plugin, the errors are not really detailed:
 ```shell script
 [ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile (default-compile) on project broken: Compilation failure -> [Help 1]
 ```
 
-While compiling without the toolchain gives the more descriptive error message:
+When using a newer version of the Maven Compiler Plugin the error message provides more detailed information:
 ```shell script
-[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile (default-compile) on project broken: Fatal error compiling: java.lang.IllegalAccessError: class lombok.javac.apt.LombokProcessor (in unnamed module @0x21bd20ee) cannot access class com.sun.tools.javac.processing.JavacProcessingEnvironment (in module jdk.compiler) because module jdk.compiler does not export com.sun.tools.javac.processing to unnamed module @0x21bd20ee -> [Help 1]
+[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.10.1:compile (default-compile) on project lombok_broken: Compilation failure
+[ERROR] java.lang.IllegalAccessError: class lombok.javac.apt.LombokProcessor (in unnamed module @...) cannot access class com.sun.tools.javac.processing.JavacProcessingEnvironme
+nt (in module jdk.compiler) because module jdk.compiler does not export com.sun.tools.javac.processing to unnamed module @...
 ```
 
-So I don't recommend the usage of Maven Toolchains for upgrading to Java 16 or 17 at this point in time.
-
 # Interesting other things
 
 ## Multi release JAR
diff --git a/java16/pom.xml b/java16/pom.xml
@@ -22,7 +22,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.8.1</version>
+                <version>3.10.1</version>
                 <configuration>
                     <release>${maven.compiler.release}</release>
                 </configuration>
@@ -32,6 +32,26 @@
                 <artifactId>maven-dependency-plugin</artifactId>
                 <version>3.1.2</version>
             </plugin>
+
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-toolchains-plugin</artifactId>
+                <version>3.0.0</version>
+                <configuration>
+                    <toolchains>
+                        <jdk>
+                            <version>17</version> <!--${maven.compiler.release}</version>-->
+                        </jdk>
+                    </toolchains>
+                </configuration>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>toolchain</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
         </plugins>
     </build>
 </project>
