Source for org.jfree.formula.lvalues.ContextLookup

   1: /**
   2:  * =========================================
   3:  * LibFormula : a free Java formula library
   4:  * =========================================
   5:  *
   6:  * Project Info:  http://reporting.pentaho.org/libformula/
   7:  *
   8:  * (C) Copyright 2006-2007, by Pentaho Corporation and Contributors.
   9:  *
  10:  * This library is free software; you can redistribute it and/or modify it under the terms
  11:  * of the GNU Lesser General Public License as published by the Free Software Foundation;
  12:  * either version 2.1 of the License, or (at your option) any later version.
  13:  *
  14:  * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
  15:  * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  16:  * See the GNU Lesser General Public License for more details.
  17:  *
  18:  * You should have received a copy of the GNU Lesser General Public License along with this
  19:  * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  20:  * Boston, MA 02111-1307, USA.
  21:  *
  22:  * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
  23:  * in the United States and other countries.]
  24:  *
  25:  *
  26:  * ------------
  27:  * $Id: ContextLookup.java 2716 2007-04-01 13:51:58Z taqua $
  28:  * ------------
  29:  * (C) Copyright 2006-2007, by Pentaho Corporation.
  30:  */
  31: package org.jfree.formula.lvalues;
  32: 
  33: import org.jfree.formula.typing.Type;
  34: import org.jfree.formula.FormulaContext;
  35: import org.jfree.formula.EvaluationException;
  36: 
  37: /**
  38:  * A reference that queries the datarow.
  39:  *
  40:  * @author Thomas Morgner
  41:  */
  42: public class ContextLookup extends AbstractLValue
  43: {
  44:   private String name;
  45: 
  46:   public ContextLookup(final String name)
  47:   {
  48:     this.name = name;
  49:   }
  50: 
  51:   public TypeValuePair evaluate() throws EvaluationException
  52:   {
  53:     final FormulaContext context = getContext();
  54:     final Object value = context.resolveReference(name);
  55:     final Type type = context.resolveReferenceType(name);
  56:     return new TypeValuePair(type, value);
  57:   }
  58: 
  59: 
  60:   public String toString()
  61:   {
  62:     return "[" +  name + "]";
  63:   }
  64: 
  65:   /**
  66:    * Checks, whether the LValue is constant. Constant lvalues always return the
  67:    * same value.
  68:    *
  69:    * @return
  70:    */
  71:   public boolean isConstant()
  72:   {
  73:     return false;
  74:   }
  75: 
  76:   public String getName()
  77:   {
  78:     return name;
  79:   }
  80: }