Multiple annotation processors under Java 16+

[igrigorov]

TLDR: Cannot build using Maven under Java 16 and some other annotation processors.

To begin with, I was very excited to find better-strings library, which, as others have mentioned, should be already in core Java, for years now. So I decided to incorporate it in my most recent project, having the following setup:

• Java 16
• Spring Boot 2.5.4
• Build tool: Maven
• Lombok
• MapStruct

There are more, but I consider these the most relevant.

Upon mvn clean install, I'm presented with an error "Compilation failure: Compilation failure".

Full stacktrace

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile (default-compile) on project boost-customer-ms: Compilation failure -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile (default-compile) on project boost-customer-ms: Compilation failure
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:215)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:78)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke (Method.java:567)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
at org.codehaus.classworlds.Launcher.main (Launcher.java:47)
Caused by: org.apache.maven.plugin.compiler.CompilationFailureException: Compilation failure
at org.apache.maven.plugin.compiler.AbstractCompilerMojo.execute (AbstractCompilerMojo.java:1224)
at org.apache.maven.plugin.compiler.CompilerMojo.execute (CompilerMojo.java:187)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:78)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke (Method.java:567)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
at org.codehaus.classworlds.Launcher.main (Launcher.java:47)

The only thing I've managed to improve is to move better-strings as last in the annotationProcessorPaths chain - when I had put it right after Lombok, I couldn't build the project at all, while if I move it at the end of the chain, the project is built successfully... until I add some string with placeholder for replacement in the code.

My current sequence of annotation paths is (I'm pasting the whole compiler plugin section):

<plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-compiler-plugin</artifactId>
	<version>3.8.1</version>
	<configuration>
		<release>${java.version}</release>
		<!-- needed any time when using <compilerArgs> -->
		<fork>true</fork>
		<!-- Needed for Lombok & Java 16 compatibility -->
		<compilerArgs>
			<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED</arg>
			<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED</arg>
			<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED</arg>
			<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED</arg>
			<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED</arg>
			<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED</arg>
			<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED</arg>
			<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED</arg>
			<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED</arg>
			<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.jvm=ALL-UNNAMED</arg>
		</compilerArgs>
		<!--for unmappable characters in classes-->
		<encoding>UTF-8</encoding>
		<showDeprecation>true</showDeprecation>
		<showWarnings>true</showWarnings>
		<!--for lombok annotations to resolve-->
		<annotationProcessorPaths>
			<path>
				<groupId>org.projectlombok</groupId>
				<artifactId>lombok</artifactId>
				<version>${lombok.version}</version>
			</path>
			<path>
				<groupId>org.mapstruct</groupId>
				<artifactId>mapstruct-processor</artifactId>
				<version>${mapstruct.version}</version>
			</path>
			<!-- This is needed when using Lombok 1.8.16 and above -->
			<path>
				<groupId>org.projectlombok</groupId>
				<artifactId>lombok-mapstruct-binding</artifactId>
				<version>${org.lombok-mapstruct-binding.version}</version>
			</path>
			<!-- This should stay last, otherwise breaks with nasty undetectable Compilation error upon Maven build -->
			<path>
				<groupId>com.antkorwin</groupId>
				<artifactId>better-strings</artifactId>
				<version>${better-strings.version}</version>
			</path>
		</annotationProcessorPaths>
		<source>${java.version}</source>
		<target>${java.version}</target>
	</configuration>
</plugin>

Maybe it's worth noting the use of lombok-mapstruct-binding - do you believe that something like that is needed in order to make better-strings work with other annotation processors too?

[igrigorov]

I was eventually able to use better-strings under Java 16+. The problem was not in the combination with other APTs, but with the imposed restrictions on using Java core libraries in this version.

After looking through the code of Better Strings, I found out it is using one more internal dependency, except for the ones I had already enabled for Lombok: com.sun.tools.javac.code. After enabling it, I was able to build using Maven (oddly enough, IntelliJ couldn't make it and still throws error upon build, but this is off-topic).

So, to help anyone else who has stuck upon this issue, the section above should look like:

<compilerArgs>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED</arg>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED</arg>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED</arg>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED</arg>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.jvm=ALL-UNNAMED</arg>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED</arg>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED</arg>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED</arg>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED</arg>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED</arg>
	<arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED</arg>
</compilerArgs>

NB: Not all of these packages need to be enabled for better-strings to work, this is the superset of packages needed for both better-strings and lombok