scala Ide无法将我的班级确定为主要方法

Question

I have researched some answers in Stackoverflow but my error seems to be different. Having said that i am a newbie in scala hence please consider that as well.

I am trying to create multi class project in scala. Project Format is like this

Test Project | COM Package | |-->App.class | COM.Test Package | |-->App1.class

Code Snippet

App.scala

object App {

  def main(args : Array[String]): Unit = {
    var logger = Logger.getLogger(this.getClass())
     if (args.length < 3) {
      logger.error("=> wrong parameters number")
      System.err.println("Usage: MainExample <path-to-files> <srcCode> <tableName>")
      System.exit(1)
    }
      println("In Main Class")
}

App1.scala

object App1 {

      def main(args : Array[String]): Unit = {
         println("In Sub Class")
    }

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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com</groupId>
  <artifactId>test</artifactId>
  <version>1.0.0</version>
  <name>${project.artifactId}</name>
  <description>My wonderfull scala app</description>
  <inceptionYear>2015</inceptionYear>
  <licenses>
    <license>
      <name>My License</name>
      <url>http://....</url>
      <distribution>repo</distribution>
    </license>
  </licenses>

  <properties>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
    <encoding>UTF-8</encoding>
    <scala.version>2.10.4</scala.version>
    <scala.compat.version>2.10.4</scala.compat.version>
  </properties>

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

  <build>
    <sourceDirectory>src/main/scala</sourceDirectory>
    <!-- >testSourceDirectory>src/test/scala</testSourceDirectory -->
    <!-- plugins>
      <plugin>
        <see http://davidb.github.com/scala-maven-plugin >
        <groupId>net.alchim31.maven</groupId>
        <artifactId>scala-maven-plugin</artifactId>
        <version>3.2.0</version>
        <executions>
          <execution>
            <goals>
              <goal>compile</goal>

            </goals>
            <configuration>
              <args>
                <arg>-make:transitive</arg>
                <arg>-dependencyfile</arg>
                <arg>${project.build.directory}/.scala_dependencies</arg>
              </args>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins -->
  </build>
</project>

I am using SCALA IDE along with Scala Maven Plugin. I have commented out the build plugin but it doen=s not make a difference if that is turned on as well.

Two Issues i am facing

Issue 1) I am unable to Run App1.scala in Sub Package COM.Test. App.scala is run without issue from Run As -->Scala Application. But when ever i try to run App1.scala the scala side is not able to find Main Class

Issue 2) I am unable to debug my code for App.scala in scala ide. Whenever i run Debug Command (Bug Operator) the breakpoints are skipped and code executes entirely. I use Scala JVM Launcher and checked The option Stop in Main. Please help

Using Eclipse Luna with Scala IDE and MAC OS

Answer 1

You need to add extends App to your main objects.

object App  extends App {

  def main(args : Array[String]): Unit = {
    var logger = Logger.getLogger(this.getClass())
     if (args.length < 3) {
      logger.error("=> wrong parameters number")
      System.err.println("Usage: MainExample <path-to-files> <srcCode> <tableName>")
      System.exit(1)
    }
      println("In Main Class")
}

Answer 2

Package structure must correspond to directory structure in the IDE. (This is unlike scalac.)

It's hard to tell from the info you present, but I can confirm that Scala IDE (on Eclipse Luna) will not offer "Run As > Scala application" if I remove the package declaration.

For example, if the class App in directory src/p/ (source file src/p/App.scala ) is not in package p , then it won't offer to run it.

Uncommenting the correct package declaration gets the run as menu back.

I can also verify that a debug config with stop in main and Scala JVM launcher works as expected for App in the default package as well as in a named package. So I don't know how that could have broken for you.