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I have a java maven project , i installed scala plugin for eclipse and added scala nature to my project . Now , i have written some custom scala Actors and some other utility classes .I am using these scala classes in my java code . while writing the code , it doesn't throw any errors .But , when i do maven clean /build , it throws compilation error's like below

11/8/11 10:45:23 AM : [ERROR] ............\Simple.java:[86,10] cannot find symbol
symbol  : variable ExecutorObject
location: class com.ms.scala.Simple
11/8/11 10:45:23 AM : [INFO] 2 errors 
11/8/11 10:45:23 AM : [INFO] -------------------------------------------------------------
11/8/11 10:45:23 AM : Build errors for Project; org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3.2:compile (default-compile) on project : Compilation failure

Eclipse IDE : helios -3.5 , Scala - 2.9.2 which comes with the plugin

i guess there is a custom compiler configuration for doing this ? i also have an other newbie question

how do you start scala actor directly in java and send a message to it ? all i can see is the act() method . i want to do this 

actor {

CustomActor ! Message

}

in java

thank you sanre6

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    Can you show us some code? It's very hard to deduce what is causing your first issue. Concerning your second question, there is no simple way to emulate Scala actor method, and hence automatically start an actor in Java (that because Java does not yet support closures). Commented Nov 8, 2011 at 7:18
  • well its actually not the code which is the problem , the same code works fine in a plain java project . But . when i use these classes in a maven project using the maven compiler plugin , i get these error's . Thanks for the explanation though regarding why actor cannot be directly used in java Commented Nov 8, 2011 at 10:14

2 Answers 2

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For the first part, have you added the scala compilation step to your maven pom? Have you added the maven-scala-plugin to your pom?

For the second part, as Mirco says, there is no simple way to define an Actor in Java. You'll have to define it in Scala, but you can then start it and send messages to it in Java.

Simply call start() on the instance, and then you should be able to pass messages to it using the ! method. This will be available in java, but it is called $bang.

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no i did not add the maven scala plugin ? So , the java compiler used by the plugin cannot compile scala classes .
The normal maven compiler plugin cannot compile scala classes. You have to add the maven scala plugin.
maven-scala-plugin solved all my issues with intermixing java/scala code . Now , i am able to run all my maven goals with the first step as compliing scala classes using the maven-scala-plugin . thanks for the hint man , you made my day
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Go to http://scala-tools.org/mvnsites/maven-scala-plugin/example_java.html and use the pom directly for a first test. I have done it with:

  1. A Scala class "ScalaUtils" inside src/main/scala
  2. A java class inside src/main/java which uses "ScalaUtils"

The important thing is to to add the scala compilation at the right phase, before java will be compiled:

<execution>
    <phase>process-resources</phase>
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Link mentioned is dead. Any new link?
Ok - found the corresponding link for scala-maven-plugin, which is what I am using: davidb.github.io/scala-maven-plugin/example_java.html

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