Scala example source code file (ScalaTool.scala)

This example Scala source code file (ScalaTool.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

ant, file, list, map, nil, path, permissiblevalue, some, stream, string, stringbuilder

The ScalaTool.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala Ant Tasks                      **
**    / __/ __// _ | / /  / _ |    (c) 2005-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala.tools.ant

import java.io.{File, InputStream, FileWriter}
import org.apache.tools.ant.BuildException
import org.apache.tools.ant.types.{Path, Reference}

/** An Ant task that generates a shell or batch script to execute a
 *  Scala program.
 *
 *  This task can take the following parameters as attributes:
 *  - `file` (mandatory),
 *  - `class` (mandatory),
 *  - `platforms`,
 *  - `classpath`,
 *  - `properties`,
 *  - `javaflags`,
 *  - `toolflags`.
 *
 * @author  Gilles Dubochet
 * @version 1.1
 */
class ScalaTool extends ScalaMatchingTask {

  private def emptyPath = new Path(getProject)

/*============================================================================*\
**                             Ant user-properties                            **
\*============================================================================*/

  abstract class PermissibleValue {
    val values: List[String]
    def isPermissible(value: String): Boolean =
      (value == "") || values.exists(_.startsWith(value))
  }

  /** Defines valid values for the platforms property. */
  object Platforms extends PermissibleValue {
    val values = List("unix", "windows")
  }

  /** The path to the exec script file. `".bat"` will be appended for the
    * Windows BAT file, if generated. */
  private var file: Option[File] = None

  /** The main class to run. */
  private var mainClass: Option[String] = None

  /** Supported platforms for the script. Either `"unix"` or `"windows"`.
    * Defaults to both. */
  private var platforms: List[String] = List("unix", "windows")

  /** An (optional) path to all JARs that this script depend on. Paths must be
    * relative to the scala home directory. If not set, all JAR archives and
    * folders in `"lib/"` are automatically added. */
  private var classpath: List[String] = Nil

  /** An (optional) path to JARs that this script depends on relative to the
    * ant project's `basedir`. */
  private var classpathPath: Path = emptyPath

  /** Comma-separated Java system properties to pass to the JRE. Properties
    * are formatted as `name=value`. Properties `scala.home`, `scala.tool.name`
    * and `scala.tool.version` are always set. */
  private var properties: List[(String, String)] = Nil

  /** Additional flags passed to the JRE (`"java [javaFlags] class"`). */
  private var javaFlags: String = ""

  /** Additional flags passed to the tool (`"java class [toolFlags]"`).
    * Can only be set when a main class is defined. */
  private var toolFlags: String = ""

/*============================================================================*\
**                             Properties setters                             **
\*============================================================================*/

  /** Sets the file attribute. */
  def setFile(input: File) =
    file = Some(input)

  /** Sets the main class attribute. */
  def setClass(input: String) =
    mainClass = Some(input)

  /** Sets the platforms attribute. */
  def setPlatforms(input: String) = {
    platforms = input.split(",").toList.flatMap { s: String =>
      val st = s.trim
      if (Platforms.isPermissible(st))
        (if (input != "") List(st) else Nil)
      else {
        buildError("Platform " + st + " does not exist.")
      }
    }
  }

  /** Sets the classpath with which to run the tool.
   *
   *  Note that this mechanism of setting the classpath is generally preferred
   *  for general purpose scripts, as this does not assume all elements are
   *  relative to the Ant `basedir`.  Additionally, the platform specific
   *  demarcation of any script variables (e.g. `${SCALA_HOME}` or
   * `%SCALA_HOME%`) can be specified in a platform independent way (e.g.
   * `@SCALA_HOME@`) and automatically translated for you.
   */
  def setClassPath(input: String) {
    classpath = classpath ::: input.split(",").toList
  }

  /**
   * A special method that allows ant classpath path definitions to be nested
   * within this ant task.
   */
  def createClassPath: Path = classpathPath.createPath()

  /**
   * Adds an Ant Path reference to the tool's classpath.
   * Note that all entries in the path must exist either relative to the project
   * basedir or with an absolute path to a file in the filesystem.  As a result,
   * this is not a mechanism for setting the classpath for more general use scripts.
   */
  def setClassPathRef(input: Reference) {
    val tmpPath = emptyPath
    tmpPath.setRefid(input)
    classpath = classpath ::: tmpPath.list.toList
  }

  /** Sets JVM properties that will be set whilst running the tool. */
  def setProperties(input: String) = {
    properties = input.split(",").toList.flatMap { s: String =>
      val st = s.trim
      val stArray = st.split("=", 2)
      if (stArray.length == 2) {
        if (input != "") List((stArray(0), stArray(1))) else Nil
      }
      else
        buildError("Property " + st + " is not formatted properly.")
    }
  }

  /** Sets flags to be passed to the Java interpreter. */
  def setJavaflags(input: String) =
    javaFlags = input.trim

  /** Sets flags to be passed to the tool. */
  def setToolflags(input: String) =
    toolFlags = input.trim

/*============================================================================*\
**                             Properties getters                             **
\*============================================================================*/

    /** Gets the value of the classpath attribute in a Scala-friendly form.
      * @return The class path as a list of files. */
    private def getUnixclasspath: String =
      transposeVariableMarkup(classpath.mkString("", ":", "").replace('\\', '/'), "${", "}")

    /** Gets the value of the classpath attribute in a Scala-friendly form.
      * @return The class path as a list of files. */
    private def getWinclasspath: String =
      transposeVariableMarkup(classpath.mkString("", ";", "").replace('/', '\\'), "%", "%")

    private def getProperties: String =
      properties.map({
        case (name,value) => "-D" + name + "=\"" + value + "\""
      }).mkString("", " ", "")

/*============================================================================*\
**                       Compilation and support methods                      **
\*============================================================================*/

    // XXX encoding and generalize
    private def getResourceAsCharStream(clazz: Class[_], resource: String): Stream[Char] = {
      val stream = clazz.getClassLoader() getResourceAsStream resource
      if (stream == null) Stream.empty
      else Stream continually stream.read() takeWhile (_ != -1) map (_.asInstanceOf[Char])
    }

    // Converts a variable like @SCALA_HOME@ to ${SCALA_HOME} when pre = "${" and post = "}"
    private def transposeVariableMarkup(text: String, pre: String, post: String) : String = {
      val chars = scala.io.Source.fromString(text)
      val builder = new StringBuilder()

      while (chars.hasNext) {
        val char = chars.next()
        if (char == '@') {
          var char = chars.next()
          val token = new StringBuilder()
          while (chars.hasNext && char != '@') {
            token.append(char)
            char = chars.next()
          }
          if (token.toString == "")
            builder.append('@')
          else
            builder.append(pre + token.toString + post)
        } else builder.append(char)
      }
      builder.toString
    }

    private def readAndPatchResource(resource: String, tokens: Map[String, String]): String = {
      val chars = getResourceAsCharStream(this.getClass, resource).iterator
      val builder = new StringBuilder()

      while (chars.hasNext) {
        val char = chars.next()
        if (char == '@') {
          var char = chars.next()
          val token = new StringBuilder()
          while (chars.hasNext && char != '@') {
            token.append(char)
            char = chars.next()
          }
          if (tokens.contains(token.toString))
            builder.append(tokens(token.toString))
          else if (token.toString == "")
            builder.append('@')
          else
            builder.append("@" + token.toString + "@")
        } else builder.append(char)
      }
      builder.toString
    }

    private def writeFile(file: File, content: String) =
      if (file.exists() && !file.canWrite())
        buildError("File " + file + " is not writable")
      else {
        val writer = new FileWriter(file, false)
        writer write content
        writer.close()
      }

/*============================================================================*\
**                           The big execute method                           **
\*============================================================================*/

  /** Performs the tool creation. */
  override def execute() = {
    // Tests if all mandatory attributes are set and valid.
    if (file.isEmpty) buildError("Attribute 'file' is not set.")
    if (mainClass.isEmpty) buildError("Main class must be set.")
    val resourceRoot = "scala/tools/ant/templates/"
    val patches = Map (
      ("class", mainClass.get),
      ("properties", getProperties),
      ("javaflags", javaFlags),
      ("toolflags", toolFlags)
    )
    // Consolidate Paths into classpath
    classpath = classpath ::: classpathPath.list.toList
    // Generate the scripts
    if (platforms contains "unix") {
      val unixPatches = patches + (("classpath", getUnixclasspath))
      val unixTemplateResource = resourceRoot + "tool-unix.tmpl"
      val unixTemplate = readAndPatchResource(unixTemplateResource, unixPatches)
      writeFile(file.get, unixTemplate)
    }
    if (platforms contains "windows") {
      val winPatches = patches + (("classpath", getWinclasspath))
      val winTemplateResource = resourceRoot + "tool-windows.tmpl"
      val winTemplate = readAndPatchResource(winTemplateResource, winPatches)
      writeFile(new File(file.get.getAbsolutePath() + ".bat"), winTemplate)
    }
  }

}