Spring Boot 2 + Java 9 + Querydsl - spring-boot

Question

I have successfully updated my application (Spring Boot + Java + Maven) to Spring Boot 2. Now I'm trying to update to Java 9.
According to Nicolas Fränkel's blog post (Migrating a Spring Boot application to Java 9 - Compatibility) I accomplished to update to Java 9 without using a module-info file. But when I create such a file, the apt-maven-plugin gets stucked on creating the Q-types.
Has anyone successfully completed using Java 9 + Maven + Querydsl?
My Maven configuration for the apt-maven-plugin looks as follows:
<plugin>
<groupId>com.mysema.maven</groupId>
<artifactId>apt-maven-plugin</artifactId>
<version>1.1.3</version>
<executions>
<execution>
<goals>
<goal>process</goal>
</goals>
<configuration>
<outputDirectory>target/generated-sources/java</outputDirectory>
<processor>com.querydsl.apt.jpa.JPAAnnotationProcessor</processor>
</configuration>
</execution>
</executions>
</plugin>
When I run mvn generate-sources, the plugin only prints a bunch of error messages, generates no classes and reports success:
$ mvn generate-sources
...
[INFO] --- apt-maven-plugin:1.1.3:process (default) # app ---
.../src/main/java/module-info.java:9: error: module not found: java.validation
requires java.validation;
^
.../src/main/java/module-info.java:13: error: module not found: hibernate.jpa
requires hibernate.jpa;
^
...
21 errors
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.484 s
[INFO] Finished at: 2018-04-01T13:11:25+02:00
[INFO] ------------------------------------------------------------------------

Answer 1

For using QueryDSL + Mapstruct and Lombok together:
<plugin>
<groupId>com.mysema.maven</groupId>
<artifactId>apt-maven-plugin</artifactId>
<dependencies>
<dependency>
<groupId>org.mapstruct</groupId>
<artifactId>mapstruct-processor</artifactId>
<version>${org.mapstruct.version}</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${lombok.version}</version>
</dependency>
</dependencies>
<executions>
<execution>
<goals>
<goal>process</goal>
</goals>
<configuration>
<outputDirectory>target/generated-sources/annotations</outputDirectory>
<processors>
<processor>lombok.launch.AnnotationProcessorHider$AnnotationProcessor</processor>
<processor>com.querydsl.apt.jpa.JPAAnnotationProcessor</processor>
<processor>org.mapstruct.ap.MappingProcessor</processor>
</processors>
</configuration>
</execution>
</executions>
</plugin>

Answer 2

querydsl is not compatible with hibernate 5.2 yet, see here https://github.com/querydsl/querydsl/issues/1917
(not related to the error you mention but good to know...)
Regarding your error, you could try to use https://plugins.gradle.org/plugin/net.ltgt.apt ? I had to use it because I was not able to use QueryDSL and Lombok together...
plugins {
id "net.ltgt.apt" version "0.12"
}
apply plugin: "net.ltgt.apt"
compileJava {
aptOptions.processors =
['com.querydsl.apt.jpa.JPAAnnotationProcessor', 'lombok.launch.AnnotationProcessorHider$AnnotationProcessor']
}

Answer 3

Instead of apt-maven-plugin, try maven-compiler-plugin.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<source>9</source>
<target>9</target>
<annotationProcessors>
<annotationProcessor>com.querydsl.apt.jpa.JPAAnnotationProcessor</annotationProcessor>
</annotationProcessors>
<annotationProcessorPaths>
<path>
<groupId>com.querydsl</groupId>
<artifactId>querydsl-core</artifactId>
<version>4.1.4</version>
</path>
<path>
<groupId>com.querydsl</groupId>
<artifactId>querydsl-apt</artifactId>
<version>4.1.4</version>
</path>
<path>
<groupId>com.mysema.codegen</groupId>
<artifactId>codegen</artifactId>
<version>0.6.8</version>
</path>
<path>
<groupId>org.eclipse.persistence</groupId>
<artifactId>javax.persistence</artifactId>
<version>2.1.0</version>
</path>
<path>
<groupId>javax.inject</groupId>
<artifactId>javax.inject</artifactId>
<version>1</version>
</path>
<path>
<groupId>javax.annotation</groupId>
<artifactId>jsr250-api</artifactId>
<version>1.0</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>
For using QueryDSL and Lombok together:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<annotationProcessors>
<annotationProcessor>lombok.launch.AnnotationProcessorHider$AnnotationProcessor</annotationProcessor>
<annotationProcessor>com.querydsl.apt.jpa.JPAAnnotationProcessor</annotationProcessor>
</annotationProcessors>
<annotationProcessorPaths>
<path>
<groupId>com.querydsl</groupId>
<artifactId>querydsl-core</artifactId>
<version>4.1.4</version>
</path>
<path>
<groupId>com.querydsl</groupId>
<artifactId>querydsl-apt</artifactId>
<version>4.1.4</version>
</path>
<path>
<groupId>com.mysema.codegen</groupId>
<artifactId>codegen</artifactId>
<version>0.6.8</version>
</path>
<path>
<groupId>org.eclipse.persistence</groupId>
<artifactId>javax.persistence</artifactId>
<version>2.1.0</version>
</path>
<path>
<groupId>javax.inject</groupId>
<artifactId>javax.inject</artifactId>
<version>1</version>
</path>
<path>
<groupId>javax.annotation</groupId>
<artifactId>jsr250-api</artifactId>
<version>1.0</version>
</path>
<path>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.22</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>

Answer 4

Improvement to the answer or yogi. This definitely works and there're no redundancies
<?xml version="1.0" encoding="UTF-8"?>
<project...>
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.4.0</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>xxx</groupId>
<artifactId>yyy</artifactId>
<version>zzz</version>
<properties>
<java.version>11</java.version>
<mapstruct.version>1.4.1.Final</mapstruct.version>
</properties>
<dependencies>
...
<dependency>
<groupId>com.querydsl</groupId>
<artifactId>querydsl-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.mapstruct</groupId>
<artifactId>mapstruct</artifactId>
<version>${mapstruct.version}</version>
</dependency>
</dependencies>
<build>
<plugins>
...
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<annotationProcessorPaths>
<path>
<groupId>org.mapstruct</groupId>
<artifactId>mapstruct-processor</artifactId>
<version>${mapstruct.version}</version>
</path>
<path>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${lombok.version}</version>
</path>
<path> <!-- Lombok made a special thing to better work with mapstruct -->
<groupId>org.projectlombok</groupId>
<artifactId>lombok-mapstruct-binding</artifactId>
<version>0.1.0</version>
</path>
<path>
<groupId>com.querydsl</groupId>
<artifactId>querydsl-apt</artifactId>
<classifier>jpa</classifier>
<version>${querydsl.version}</version>
</path>
<path>
<groupId>javax.annotation</groupId>
<artifactId>javax.annotation-api</artifactId>
<version>${javax-annotation.version}</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>
</plugins>
</build>
</project>