How can I make scala-maven-plugin make see classes compiled by maven-compiler-plugin?

Question

I can't use the scala-maven-plugin to build my Java-sources due to a bug in Scalac (https://issues.scala-lang.org/browse/SI-9853).

Splitting the build so that Java is compiled by the maven-compiler-plugin and Scala by the scala-maven-plugin was easy enough with the sources residing in src/main/java and src/main/scala. Right now I am running into the problem that the Scala-classes can't see the Java-classes. When doing mvn clean compile I get 'not found' for all Java-classes required by the Scala-classes. Checking 'target/classes' shows that the Java-classes are there.

I tried moving the Scala-build to different phases but the results remain the same.

How can I make the Scala-build see the classes already available in target/classes?

<?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>de.codepitbull.maven</groupId>
    <artifactId>maven-scalac-bug</artifactId>
    <version>3.4.0-SNAPSHOT</version>

    <name>Scalac + Javac</name>

    <properties>
        <scala.version>2.11.8</scala.version>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-library</artifactId>
            <version>${scala.version}</version>
        </dependency>
        <dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-compiler</artifactId>
            <scope>provided</scope>
            <version>${scala.version}</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <executions>
                    <execution>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>net.alchim31.maven</groupId>
                <artifactId>scala-maven-plugin</artifactId>
                <version>3.2.2</version>
                <configuration>
                    <sendJavaToScalac>false</sendJavaToScalac>
                    <args>
                        <arg>-target:jvm-1.8</arg>
                        <arg>-feature</arg>
                        <arg>-deprecation</arg>
                        <arg>-explaintypes</arg>
                        <arg>-unchecked</arg>
                        <arg>-Xlint</arg>
                    </args>
                </configuration>
                <executions>
                    <execution>
                        <id>java-compile-first</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Achim Nierbeck Achim Nierbeck · Accepted Answer · 2016-07-21T05:42:13

The easiest workaround would be to split it into two submodules. That way you're able to reference the Java classes as dependency. After that generate an Uber jar or shaded jar with both modules inlined.

How can I make scala-maven-plugin make see classes compiled by maven-compiler-plugin?

1 Answers