Failed to execute maven-compiler-plugin:3.6.1:testCompile when using java 9

Question

I know that there are a lot question with similar error. I would appreciate before point as duplicate take in account that it only happens with Java 9.

I do have java 9 installed

C:\_pocs\ws_j9\java9-http-client>java -version
java version "9.0.1"
Java(TM) SE Runtime Environment (build 9.0.1+11)
Java HotSpot(TM) 64-Bit Server VM (build 9.0.1+11, mixed mode)

C:\_pocs\ws_j9\java9-http-client>echo %JAVA_HOME%
C:\Program Files\Java\jdk-9.0.1

To make simple the exemplification, if i download a very simple example https://examples.javacodegeeks.com/core-java/java-9-httpclient-example/ and I try/

mvn clean install package -e

[ERROR] Failed to parse module-info:
[ERROR] With qdox: null
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.925 s
[INFO] Finished at: 2018-01-01T23:43:32+01:00
[INFO] Final Memory: 13M/44M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.6.1:testCompile (default-testCompile) on project http_client: Execution default-testCompile of goal org.apache.maven.plugins:maven-compiler-plugin:3.6.1:testCompile failed: Failed to parse module-info -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.6.1:testCompile (default-testCompile) on project http_client: Execution default-testCompile of goal org.apache.maven.plugins:maven-compiler-plugin:3.6.1:testCompile failed: Failed to parse module-info
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:213)

pom.xml

<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.javacodegeeks.java9</groupId>
    <artifactId>http_client</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Java9HttpClient</name>
    <description>Java Http Client example</description>
    <properties>
        <java-version>1.9</java-version>

        <maven-compiler-plugin-version>3.6.1</maven-compiler-plugin-version>
        <maven-shade-plugin-version>3.0.0</maven-shade-plugin-version>
    </properties>

    <build>
        <pluginManagement>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>${maven-compiler-plugin-version}</version>
                </plugin>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-shade-plugin</artifactId>
                    <version>${maven-shade-plugin-version}</version>
                </plugin>
            </plugins>
        </pluginManagement>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>${java-version}</source>
                    <target>${java-version}</target>
                    <verbose>true</verbose>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <transformers>
                                <transformer
                                    implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>com.javacodegeeks.java9.http_client.Main</mainClass>
                                </transformer>
                            </transformers>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

I am bit confused what could be causing this issue. On top of this, I am facing another challenge that make it a bit harder for someone trying to use Java 9 for first time: my Eclipse isn't properly accepting Java 9. I tried install Java 9 Support in Eclipse Oxygen which I just downloaded it but I am getting "No repository found at http://download.eclipse.org/eclipse/updates/none". And I can't make this mvn plugin update the Java version to 9 (it used to work properly for Java < 1.8:

    <properties>
        <java-version>1.9</java-version>
...
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>${java-version}</source>
                    <target>${java-version}</target>
                    <verbose>true</verbose>
                </configuration>
            </plugin>

That is the reason I am trying to compile straich from command line.

I read that Java 9 came with new concept of modularity which will help us better organize the packages but I am very limeted if this could drive me to fix my issue. It might be some obvious solution whe someone sees "Failed to parse module-info" but I can't imagine anything usefull to try.

My straight question is what I could check in order to compile. An additional trick regard making Eclipse Oxygen current version compatible with Java 9 will be appreciatte as well.

• Edited

Eclipse version downloaded for Windows less than 24 hours ago:

Eclipse Java EE IDE for Web Developers.

Version: Oxygen.2 Release (4.7.2) Build id: 20171218-0600

• Edited second time

After I changed from 1.9 to 9 the red error icon was gone and I have now Java 9. Nevertheless, now I got this error:

[ERROR] COMPILATION ERROR : 
[INFO] -------------------------------------------------------------
[ERROR] No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?
[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.542 s
[INFO] Finished at: 2018-01-02T05:19:30+01:00
[INFO] Final Memory: 9M/30M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.7.0:compile (default-compile) on project http_client: Compilation failure
[ERROR] No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?

Which doesn't make sense to me because:

• Edited third time

Answer 1

In short, add a missing/misplaced class named module-info.java to include your project's module declaration at your project's source root. (e.g src/main/java)

Additionally, note to upgrade to the version 3.7.0 of the maven-compiler-plugin in case you have a comment included in your module-info class. [The logs seems pretty relevant to this.]

---

Or the other way, if you wish to compile your project with a previous version of Java then use the release flag as:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.7.0</version>
    <configuration>
        <release>8</release>
        <verbose>true</verbose>
    </configuration>
</plugin>

---

Concepts

With Java9 marking the completion of the project Jigsaw therein introducing the Java Platform Module System (JPMS), projects build on Java version 9 and above would be modularised. This would include a primary compiled class called module-info.class which is that module's declaration.

The initial draft and eventually The State of the Module System describes best over the concepts followed and practiced.

---

An additional trick regard making Eclipse Oxygen current version compatible with Java 9

AFAIK the latest Oxygen builds (Oxygen.2 at this point in time) from Eclipse are meant to be Java9 compatible without any additional plugin support anymore.

---

Additional Useful Resources:

• JDK9 Migration Guide

• Maven compiler plugin's example over module-info inclusion and exclusion