1   /**
    2    * Licensed under the Artistic License; you may not use this file
    3    * except in compliance with the License.
    4    * You may obtain a copy of the License at
    5    *
    6    *      http://displaytag.sourceforge.net/license.html
    7    *
    8    * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR
    9    * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
   10    * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
   11    */
   12   package org.displaytag.tags.el;
   13   
   14   import javax.servlet.jsp.JspException;
   15   import javax.servlet.jsp.PageContext;
   16   import javax.servlet.jsp.tagext.Tag;
   17   
   18   import org.apache.commons.lang.BooleanUtils;
   19   import org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager;
   20   
   21   
   22   /**
   23    * Utility class to help with the evaluation of JSTL Expression Language. It mainly encapsulates the calls to
   24    * ExpressionEvaluationManager to ease the use of this class.
   25    * @author Tim McCune
   26    * @author Fabrizio Giustina
   27    * @version $Revision: 1081 $ ($Author: fgiust $)
   28    */
   29   public class ExpressionEvaluator
   30   {
   31   
   32       /**
   33        * page context.
   34        */
   35       private PageContext pageContext;
   36   
   37       /**
   38        * tag.
   39        */
   40       private Tag tag;
   41   
   42       /**
   43        * Creates a new ExpressionEvaluator for the given tag and pagecontext.
   44        * @param sourceTag tag where the expression has to be evaluated
   45        * @param context the page context
   46        */
   47       public ExpressionEvaluator(Tag sourceTag, PageContext context)
   48       {
   49           this.tag = sourceTag;
   50           this.pageContext = context;
   51       }
   52   
   53       /**
   54        * Evaluate expression in attrValue.
   55        * @param attrName attribute name
   56        * @param attrValue attribute value
   57        * @return evaluate expression of attrValue, null if attrValue is null.
   58        * @param returnClass class the returned object is instance of
   59        * @throws JspException exception thrown by ExpressionEvaluatorManager
   60        */
   61       public Object eval(String attrName, String attrValue, Class returnClass) throws JspException
   62       {
   63           return attrValue != null ? ExpressionEvaluatorManager.evaluate(
   64               attrName,
   65               attrValue,
   66               returnClass,
   67               this.tag,
   68               this.pageContext) : null;
   69       }
   70   
   71       /**
   72        * Evaluate expression in attrValueas as a String.
   73        * @param attrName attribute name
   74        * @param attrValue attribute value
   75        * @return evaluate expression of attrValue, null if attrValue is null.
   76        * @throws JspException exception thrown by ExpressionEvaluatorManager
   77        */
   78       public String evalString(String attrName, String attrValue) throws JspException
   79       {
   80           return (String) eval(attrName, attrValue, String.class);
   81       }
   82   
   83       /**
   84        * Evaluate expression in attrValueas as a boolean.
   85        * @param attrName attribute name
   86        * @param attrValue attribute value
   87        * @return evaluate expression of attrValue, false if attrValue is null.
   88        * @throws JspException exception thrown by ExpressionEvaluatorManager
   89        */
   90       public boolean evalBoolean(String attrName, String attrValue) throws JspException
   91       {
   92           return BooleanUtils.toBoolean((Boolean) eval(attrName, attrValue, Boolean.class));
   93       }
   94   
   95       /**
   96        * Evaluate expression in attrValueas as a long.
   97        * @param attrName attribute name
   98        * @param attrValue attribute value
   99        * @return evaluate expression of attrValue, -1 if attrValue is null.
  100        * @throws JspException exception thrown by ExpressionEvaluatorManager
  101        */
  102       public long evalLong(String attrName, String attrValue) throws JspException
  103       {
  104           Long rtn = (Long) eval(attrName, attrValue, Long.class);
  105           if (rtn != null)
  106           {
  107               return rtn.longValue();
  108           }
  109   
  110           return -1L;
  111       }
  112   
  113       /**
  114        * Evaluate expression in attrValueas as a int.
  115        * @param attrName attribute name
  116        * @param attrValue attribute value
  117        * @return evaluate expression of attrValue, -1 if attrValue is null.
  118        * @throws JspException exception thrown by ExpressionEvaluatorManager
  119        */
  120       public int evalInt(String attrName, String attrValue) throws JspException
  121       {
  122           Integer rtn = (Integer) eval(attrName, attrValue, Integer.class);
  123           if (rtn != null)
  124           {
  125               return rtn.intValue();
  126           }
  127   
  128           return -1;
  129       }
  130   }