https://wiki.eclipse.org/UserGuide/JPA/Using_the_Canonical_Model_Generator_(ELUG)
Succeeded as below.
# With javac
javac \
-encoding UTF-8 \
-Xlint:all \
--release 9 \
--add-modules java.xml.ws.annotation \
--processor-path \
${HOME}/.m2/repository/org/projectlombok/lombok/1.16.20/lombok-1.16.20.jar:\
${HOME}/.m2/repository/org/eclipse/persistence/org.eclipse.persistence.antlr/2.7.1/org.eclipse.persistence.antlr-2.7.1.jar:\
${HOME}/.m2/repository/org/eclipse/persistence/org.eclipse.persistence.asm/2.7.1/org.eclipse.persistence.asm-2.7.1.jar:\
${HOME}/.m2/repository/org/eclipse/persistence/org.eclipse.persistence.core/2.7.1/org.eclipse.persistence.core-2.7.1.jar:\
${HOME}/.m2/repository/org/eclipse/persistence/org.eclipse.persistence.jpa/2.7.1/org.eclipse.persistence.jpa-2.7.1.jar:\
${HOME}/.m2/repository/org/eclipse/persistence/org.eclipse.persistence.jpa.jpql/2.7.1/org.eclipse.persistence.jpa.jpql-2.7.1.jar:\
${HOME}/.m2/repository/org/eclipse/persistence/org.eclipse.persistence.jpa.modelgen.processor/2.7.1/org.eclipse.persistence.jpa.modelgen.processor-2.7.1.jar:\
${HOME}/.m2/repository/org/eclipse/persistence/javax.persistence/2.2.0/javax.persistence-2.2.0.jar:\
${HOME}/.m2/repository/javax/annotation/javax.annotation-api/1.3.1/javax.annotation-api-1.3.1.jar:\
-Aeclipselink.persistencexml=../resources/META-INF/persistence-ap.xml \
--class-path \
${HOME}/.m2/repository/org/projectlombok/lombok/1.16.20/lombok-1.16.20.jar:\
${HOME}/.m2/repository/org/eclipse/persistence/javax.persistence/2.2.0/javax.persistence-2.2.0.jar:\
${HOME}/.m2/repository/org/slf4j/slf4j-api/1.7.25/slf4j-api-1.7.25.jar:\
$(find -type f -name *.java)<!-- With maven -->
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>9</maven.compiler.source>
<maven.compiler.target>9</maven.compiler.target>
<maven.compiler.release>9</maven.compiler.release>
<prerequisites.maven>3.5.0</prerequisites.maven>
</properties>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<annotationProcessorPaths>
<path>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.20</version>
</path>
<path>
<groupId>org.eclipse.persistence</groupId>
<artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
<version>2.7.1</version>
</path>
<path>
<!--
[Workaround for ...]
An annotation processor threw an uncaught exception.
Consult the following stack trace for details.
java.lang.NoClassDefFoundError: javax/annotation/Generated
at org.eclipse.persistence.internal.jpa.modelgen.MetadataMirrorFactory.setEnvironments(MetadataMirrorFactory.java:327)
at org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor.process(CanonicalModelProcessor.java:391)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(JavacProcessingEnvironment.java:968)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(JavacProcessingEnvironment.java:884)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.access$2200(JavacProcessingEnvironment.java:108)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(JavacProcessingEnvironment.java:1206)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:1315)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1246)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:922)
at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:302)
at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:162)
at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:57)
at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:43)
Caused by: java.lang.ClassNotFoundException: javax.annotation.Generated
at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:466)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:563)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:496)
... 13 more
-->
<groupId>javax.annotation</groupId>
<artifactId>javax.annotation-api</artifactId>
<version>1.3.1</version>
</path>
</annotationProcessorPaths>
<compilerArgs>
<arg>-Xlint:all</arg>
<arg>--add-modules=java.xml.ws.annotation</arg>
<arg>-Aeclipselink.persistencexml=${basedir}/src/main/resources/META-INF/persistence-ap.xml</arg>
</compilerArgs>
<forceJavacCompilerUse>true</forceJavacCompilerUse>
<fork>true</fork>
<showDeprecation>true</showDeprecation>
<showWarnings>true</showWarnings>
</configuration>
</plugin>However, the model generated by Maven (above) is not recognized by Apache Netbeans (Incubating) RC 3.