javaeclipsescalamavenjboss-developer-studio

Can't see scala classes from Main.java in Java-Scala maven project


I'm following tutorial here: http://scala-tools.org/mvnsites/maven-scala-plugin/example_java.html to have java with scala files in the same project

however mvn compile fails with error: cannot find symbol
apparently complaining about places where the only scala class is being referenced.

Here is my project structure:

.   
├── pom.xml
├── src 
│   ├── main
│   │   ├── java
│   │   │   └── com 
│   │   │       └── dummy
│   │   │           └── foo 
│   │   │               ├── Foo.java
│   │   │               └── Main.java
│   │   ├── resources
│   │   └── scala
│   │       └── com 
│   │           └── dummy
│   │               └── hello
│   │                   └── Hello.scala
│   └── test
│       ├── java
│       ├── resources
│       └── scala
├── tree-pre-compile

And here it is again after running (the failing) mvn compile: (I can see that Hello.class is there under target/classes)

.
├── pom.xml
├── src
│   ├── main
│   │   ├── java
│   │   │   └── com
│   │   │       └── dummy
│   │   │           └── foo
│   │   │               ├── Foo.java
│   │   │               └── Main.java
│   │   ├── resources
│   │   └── scala
│   │       └── com
│   │           └── dummy
│   │               └── hello
│   │                   └── Hello.scala
│   └── test
│       ├── java
│       ├── resources
│       └── scala
├── target
│   ├── classes
│   │   ├── Hello.class
│   │   └── META-INF
│   │       ├── MANIFEST.MF
│   │       └── maven
│   │           └── com.dummy.java-scala-poc
│   │               └── mixed-java-scala-poc
│   │                   ├── pom.properties
│   │                   └── pom.xml
│   ├── classes.timestamp
│   └── test-classes
└── tree-text

Main.java:

package com.dummy.foo;

public class Main {

  public static void main(String[] args) {
    System.out.print("mixing java and scala");
    Foo foo = new Foo();
    foo.foo();
    new Hello().hello();
  }   

} 

Foo.java:

package com.dummy.foo;

public class Foo {
  public void foo() {
    System.out.print("mixing java and scala");
    new Hello().hello();
  } 
}  

Hello.scala:

class Hello {
  def hello() { println("Hello (class)") }
}

object Hello {
  def hello() { println("Hello (object)") }
}

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.dummy.java-scala-poc</groupId>
  <artifactId>mixed-java-scala-poc</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>mixed-java-scala-poc</name>
  <packaging>jar</packaging>

  <dependencies>
        <dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-library</artifactId>
            <version>2.11.8</version>
        </dependency>
    </dependencies>
    <repositories>
        <repository>
            <id>scala-tools.org</id>
            <name>Scala-tools Maven2 Repository</name>
            <url>http://scala-tools.org/repo-releases</url>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>scala-tools.org</id>
            <name>Scala-tools Maven2 Repository</name>
            <url>http://scala-tools.org/repo-releases</url>
        </pluginRepository>
    </pluginRepositories>

    <build>
        <pluginManagement>
            <plugins>
                <plugin>
                    <groupId>org.scala-tools</groupId>
                    <artifactId>maven-scala-plugin</artifactId>
                    <version>2.9.1</version>
                </plugin>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>2.0.2</version>
                </plugin>
            </plugins>
        </pluginManagement>
        <plugins>
            <plugin>
                <groupId>org.scala-tools</groupId>
                <artifactId>maven-scala-plugin</artifactId>
                <executions>
                    <execution>
                        <id>scala-compile-first</id>
                        <phase>process-resources</phase>
                        <goals>
                            <goal>add-source</goal>
                            <goal>compile</goal>
                        </goals>
                    </execution>                                    
                    <execution>
                        <id>scala-test-compile</id>
                        <phase>process-test-resources</phase>
                        <goals>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <executions>
                    <execution>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

IDE being used is JBoss Developer Studio Version: 8.1.0.GA

I can find other questions on SO with similar issues but to my best efforts nothing seemed to work.

Here is the mvn compile output:

[INFO] Scanning for projects...
[INFO]    
[INFO] ------------------------------------------------------------------------
[INFO] Building mixed-java-scala-poc 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-resources-plugin:2.3:resources (default-resources) @ mixed-java-scala-poc --- 
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 0 resource
[INFO] 
[INFO] --- maven-scala-plugin:2.9.1:add-source (scala-compile-first) @ mixed-java-scala-poc --- 
[INFO] Add Source directory: /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/main/scala
[INFO] Add Test Source directory: /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/test/scala
[INFO] 
[INFO] --- maven-scala-plugin:2.9.1:compile (scala-compile-first) @ mixed-java-scala-poc --- 
[ERROR] /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/main/java
[ERROR] /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/main/scala
[ERROR] /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/test/scala
[INFO] Compiling 3 source files to /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/target/classes
[INFO] 
[INFO] --- maven-compiler-plugin:2.0.2:compile (default-compile) @ mixed-java-scala-poc --- 
[INFO] Compiling 2 source files to /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/target/classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.301s
[INFO] Finished at: Thu Apr 28 15:25:55 EEST 2016
[INFO] Final Memory: 12M/145M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.0.2:compile (default-compile) on project mixed-java-scala-poc: Compilation failure: Compilation failure:
[ERROR] /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/main/java/com/dummy/foo/Foo.java:[6,8] error: cannot find symbol
[ERROR] 
[ERROR] could not parse error message:   symbol:   class Hello
[ERROR] location: class Foo 
[ERROR] /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/main/java/com/dummy/foo/Main.java:9: error: cannot find symbol
[ERROR] new Hello().hello();
[ERROR] ^
[ERROR] -> [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/MojoFailureException

Solution

  • Solved it,

    Downloaded and installed Scala IDE plugin for eclipse by following guide at http://scala-ide.org/docs/current-user-doc/gettingstarted/index.html which in turn (the plugin) pointed me to issues...

    Silly me, I was missing package declaration in Hello.scala and imports in Main.java and Foo.java, the files now look like this:

    Hello.scala:

    package com.dummy.hello;
    
    class Hello {
      def hello() { println("Hello (class)") }
    }
    
    object Hello {
      def hello() { println("Hello (object)") }
    }
    

    Foo.java:

    package com.dummy.foo;
    
    import com.dummy.hello.Hello;
    
    public class Foo {
      public void foo() {
        System.out.print("mixing java and scala");
        new Hello().hello();
      }
    }
    

    Main.java:

    package com.dummy.foo;
    
    import com.dummy.hello.Hello;
    
    public class Main {
      public static void main(String[] args) {
        System.out.print("mixing java and scala");
        Foo foo = new Foo();
        foo.foo();
        new Hello().hello();
      }
    }
    

    I hope someone finds this helpful.