Package org.pentaho.reporting.engine.classic.extensions.modules.rhino

Source Code of org.pentaho.reporting.engine.classic.extensions.modules.rhino.RhinoExpression

/*
* This program is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
* Foundation.
*
* You should have received a copy of the GNU Lesser General Public License along with this
* program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
* or from the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* 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 Lesser General Public License for more details.
*
* Copyright (c) 2005 - 2009 Pentaho Corporation, Object Refinery Limited and Contributors.  All rights reserved.
*/

package org.pentaho.reporting.engine.classic.extensions.modules.rhino;

import java.io.Serializable;

import org.pentaho.reporting.engine.classic.core.function.AbstractExpression;
import org.pentaho.reporting.engine.classic.core.states.LegacyDataRowWrapper;
import org.mozilla.javascript.Scriptable;
import org.mozilla.javascript.Context;
import org.mozilla.javascript.ScriptableObject;

/**
* An expression that uses the Rhino scripting framework to perform a scripted
* calculation. The expression itself is contained in a function called
* <p/>
* <code>Object getValue()</code>
* <p/>
* and this function is defined in the <code>expression</code> property. You have to
* overwrite the function <code>getValue()</code> to begin and to end your expression, but
* you are free to add your own functions to the script.
* <p/>
*
* @author Thomas Morgner
*/
public class RhinoExpression extends AbstractExpression implements Serializable
{
  private String expression;

  /**
   * default constructor, create a new BeanShellExpression.
   */
  public RhinoExpression()
  {
  }


  protected void initializeScope (final Scriptable scope)
  {
    final LegacyDataRowWrapper dataRowWrapper = new LegacyDataRowWrapper();
    final Object wrappedDataRow = Context.javaToJS(dataRowWrapper, scope);
    ScriptableObject.putProperty(scope, "dataRow", wrappedDataRow);
  }

  /**
   * Evaluates the defined expression. If an exception or an evaluation error occures, the
   * evaluation returns null and the error is logged. The current datarow and a copy of
   * the expressions properties are set to script-internal variables. Changes to the
   * properties will not alter the expressions original properties and will be lost when
   * the evaluation is finished.
   * <p/>
   * Expressions do not maintain a state and no assumptions about the order of evaluation
   * can be made.
   *
   * @return the evaluated value or null.
   */
  public Object getValue ()
  {
    if (expression == null)
    {
      return null;
    }

    try
    {
      final Context context = Context.enter();
      final Scriptable scope = context.initStandardObjects();
      initializeScope(scope);

      return context.evaluateString(scope, expression, getName(), 1, null);
    }
    finally
    {
      Context.exit();
    }
  }

  public String getExpression ()
  {
    return expression;
  }

  public void setExpression (final String expression)
  {
    this.expression = expression;
  }
}
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