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The Waikato Environment for Knowledge Analysis (WEKA), a machine learning workbench. This version represents the developer version, the "bleeding edge" of development, you could say. New functionality gets added to this version.
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/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see .
 */

/*
 * Groovy.java
 * Copyright (C) 2009-2012 University of Waikato, Hamilton, New Zealand
 */

package weka.core.scripting;

import java.io.File;
import java.io.Serializable;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;

import weka.core.RevisionHandler;
import weka.core.RevisionUtils;
import weka.core.WekaPackageClassLoaderManager;

/**
 * A helper class for Groovy.
 * 
 * In order to use Groovy, the jar containing all the classes must be present in
 * the CLASSPATH. This jar is normally found in the embeddable
 * sub-directory of the Groovy installation.
 * 
 * Tested with Groovy 1.5.7.
 * 
 * @author fracpete (fracpete at waikato dot ac dot nz)
 * @version $Revision: 13692 $
 */
public class Groovy implements Serializable, RevisionHandler {

  /** for serialization. */
  private static final long serialVersionUID = -2628766602043134673L;

  /** the classname of the Groovy classloader. */
  public final static String CLASS_GROOVYCLASSLOADER = "groovy.lang.GroovyClassLoader";

  /** whether the Groovy classes are in the Classpath. */
  protected static boolean m_Present = false;
  static {
    try {
      // Class.forName(CLASS_GROOVYCLASSLOADER);
      WekaPackageClassLoaderManager.forName(CLASS_GROOVYCLASSLOADER);
      m_Present = true;
    } catch (Exception e) {
      m_Present = false;
    }
  }

  /** the classloader. */
  protected Object m_ClassLoader;

  /**
   * default constructor, tries to instantiate a Groovy classloader.
   */
  public Groovy() {
    m_ClassLoader = newClassLoader();
  }

  /**
   * returns the currently used Groovy classloader.
   * 
   * @return the classloader, can be null
   */
  public Object getClassLoader() {
    return m_ClassLoader;
  }

  /**
   * executes the specified method on the current interpreter and returns the
   * result, if any.
   * 
   * @param methodName the name of the method
   * @param paramClasses the classes of the parameters
   * @param paramValues the values of the parameters
   * @return the return value of the method, if any (in that case null)
   */
  public Object invoke(String methodName, Class[] paramClasses,
    Object[] paramValues) {
    Object result;

    result = null;
    if (getClassLoader() != null) {
      result = invoke(getClassLoader(), methodName, paramClasses, paramValues);
    }

    return result;
  }

  /**
   * returns whether the Groovy classes are present or not, i.e. whether the
   * classes are in the classpath or not
   * 
   * @return whether the Groovy classes are available
   */
  public static boolean isPresent() {
    return m_Present;
  }

  /**
   * initializes and returns a Groovy Interpreter.
   * 
   * @return the interpreter or null if Groovy classes not present
   */
  public static Object newClassLoader() {
    Object result;
    Class cls;
    Constructor constr;

    result = null;

    if (isPresent()) {
      try {
        // cls = Class.forName(CLASS_GROOVYCLASSLOADER);
        cls = WekaPackageClassLoaderManager.forName(CLASS_GROOVYCLASSLOADER);
        constr = cls.getConstructor(new Class[] { ClassLoader.class });
        //result = constr.newInstance(Groovy.class.getClassLoader());
        result = constr.newInstance(cls.getClassLoader());
      } catch (Exception e) {
        e.printStackTrace();
        result = null;
      }
    }

    return result;
  }

  /**
   * loads the module and returns a new instance of it as instance of the
   * provided Java class template.
   * 
   * @param file the Groovy module file
   * @param template the template for the returned Java object
   * @return the Groovy object
   */
  public static Object newInstance(File file, Class template) {
    Object result;
    Object interpreter;
    Class cls;

    result = null;

    if (!isPresent()) {
      return result;
    }

    interpreter = newClassLoader();
    if (interpreter == null) {
      return result;
    }

    try {
      cls = (Class) invoke(interpreter, "parseClass",
        new Class[] { File.class }, new Object[] { file });
      result = cls.newInstance();
    } catch (Exception e) {
      e.printStackTrace();
    }

    return result;
  }

  /**
   * executes the specified method and returns the result, if any.
   * 
   * @param o the object the method should be called from, e.g., a Groovy
   *          Interpreter
   * @param methodName the name of the method
   * @param paramClasses the classes of the parameters
   * @param paramValues the values of the parameters
   * @return the return value of the method, if any (in that case null)
   */
  public static Object invoke(Object o, String methodName,
    Class[] paramClasses, Object[] paramValues) {
    Method m;
    Object result;

    result = null;

    try {
      m = o.getClass().getMethod(methodName, paramClasses);
      result = m.invoke(o, paramValues);
    } catch (Exception e) {
      e.printStackTrace();
      result = null;
    }

    return result;
  }

  /**
   * Returns the revision string.
   * 
   * @return the revision
   */
  @Override
  public String getRevision() {
    return RevisionUtils.extract("$Revision: 13692 $");
  }

  /**
   * If no arguments are given, it just prints the presence of the Groovy
   * classes, otherwise it expects a Groovy filename to execute.
   * 
   * @param args commandline arguments
   */
  public static void main(String[] args) {
    if (args.length == 0) {
      System.out.println("Groovy present: " + isPresent());
    } else {
      Groovy groovy = new Groovy();
      if (groovy.getClassLoader() == null) {
        System.err.println("Cannot instantiate Groovy ClassLoader!");
      } else {
        Object groovyObject = Groovy.newInstance(new File(args[0]),
          Object.class);
        Groovy.invoke(groovyObject, "run", new Class[] {}, new Object[] {});
      }
    }
  }
}