fatal error compiling invalid flag --module-path
I have a project. Originally it was a single module project with structure like this
java-cloud-sample\
src\
main\
java
pom.xml
I decided to make it into a multi-module structure - I use java 9 anyway.
So I separated it like this
java-cloud-sample\
java-cloud-rest-api\
src\
pom.xml
pom.xml
Where root pom.xml looks like this
<?xml version="1.0" encoding="UTF-8"?>
<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>com.lapots.breed.platform.cloud</groupId>
<artifactId>java-cloud-sample</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>pom</packaging>
<modules>
<module>java-cloud-rest-api</module>
</modules>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.6.RELEASE</version>
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<maven.compiler.source>1.9</maven.compiler.source>
<maven.compiler.target>1.9</maven.compiler.target>
</properties>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.6.2</version>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>3.0.0</version>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>3.0.1</version>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>package</phase>
<goals><goal>copy-dependencies</goal></goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
And module pom.xml looks like this
<?xml version="1.0" encoding="UTF-8"?>
<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>
<parent>
<groupId>com.lapots.breed.platform.cloud</groupId>
<artifactId>java-cloud-sample</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<artifactId>java-cloud-rest-api</artifactId>
<description>Demo project for Spring Boot</description>
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>build-info</goal>
</goals>
<configuration>
<additionalProperties>
<encoding.source>${project.build.sourceEncoding}</encoding.source>
<encoding.reporting>${project.reporting.outputEncoding}</encoding.reporting>
<java.source>${maven.compiler.source}</java.source>
<java.target>${maven.compiler.target}</java.target>
</additionalProperties>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
But when I try to run mvn clean package I get
INFO] java-cloud-rest-api ................................ FAILURE [ 1.060 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.104 s
[INFO] Finished at: 2017-09-08T17:15:46+03:00
[INFO] Final Memory: 27M/331M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.6.2:compile (default-compile) on project java-cloud-rest-api: Fatal error compiling: invalid flag: --module-path -> [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
[ERROR]
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR] mvn <goals> -rf :java-cloud-rest-api
What is the problem? (maybe I should split maven project into separate modules and each maven module split into java modules)
Answer
This failure occurs when maven installed on your machine is configured with java8 as the default java version. You can confirm this by executing
mvn -version
on your terminal and checking the Java version stated in the configuration.
To resolve the version to a newer and supported version like java9 at the moment, you can create/edit the mavenrc(on MacOS) file on your machine:
vi ~/.mavenrc
to include these
export PATH
export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home/
export PATH=${PATH}:$JAVA_HOME/bin
Once you save this configuration, you can confirm maven should be using Java version 9 using the same command and then your project shall build without the stated error.