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;
   13   
   14   import javax.servlet.jsp.PageContext;
   15   import javax.servlet.jsp.tagext.BodyTagSupport;
   16   
   17   import org.displaytag.exception.ObjectLookupException;
   18   import org.displaytag.util.LookupUtil;
   19   
   20   
   21   /**
   22    * Base template class.
   23    * @author bgsmith
   24    * @author Fabrizio Giustina
   25    * @version $Revision: 1081 $ ($Author: fgiust $)
   26    */
   27   public abstract class TemplateTag extends BodyTagSupport
   28   {
   29   
   30       /**
   31        * <p>
   32        * evaluate an expression in a way similar to LE in jstl.
   33        * </p>
   34        * <p>
   35        * the first token is supposed to be an object in the page scope (default scope) or one of the following:
   36        * </p>
   37        * <ul>
   38        * <li>pageScope</li>
   39        * <li>requestScope</li>
   40        * <li>sessionScope</li>
   41        * <li>applicationScope</li>
   42        * </ul>
   43        * <p>
   44        * Tokens after the object name are interpreted as javabean properties (accessed through getters), mapped or indexed
   45        * properties, using the jakarta common-beans library
   46        * </p>
   47        * @param expression expression to evaluate
   48        * @return Object result
   49        * @throws ObjectLookupException if unable to get a bean using the given expression
   50        */
   51       protected Object evaluateExpression(String expression) throws ObjectLookupException
   52       {
   53   
   54           String expressionWithoutScope = expression;
   55   
   56           // default scope = request
   57           // this is for compatibility with the previous version, probably default should be PAGE
   58           int scope = PageContext.REQUEST_SCOPE;
   59   
   60           if (expression.startsWith("pageScope.")) //$NON-NLS-1$
   61           {
   62               scope = PageContext.PAGE_SCOPE;
   63               expressionWithoutScope = expressionWithoutScope.substring(expressionWithoutScope.indexOf('.') + 1);
   64           }
   65           else if (expression.startsWith("requestScope.")) //$NON-NLS-1$
   66           {
   67               scope = PageContext.REQUEST_SCOPE;
   68               expressionWithoutScope = expressionWithoutScope.substring(expressionWithoutScope.indexOf('.') + 1);
   69   
   70           }
   71           else if (expression.startsWith("sessionScope.")) //$NON-NLS-1$
   72           {
   73               scope = PageContext.SESSION_SCOPE;
   74               expressionWithoutScope = expressionWithoutScope.substring(expressionWithoutScope.indexOf('.') + 1);
   75   
   76           }
   77           else if (expression.startsWith("applicationScope.")) //$NON-NLS-1$
   78           {
   79               scope = PageContext.APPLICATION_SCOPE;
   80               expressionWithoutScope = expressionWithoutScope.substring(expressionWithoutScope.indexOf('.') + 1);
   81   
   82           }
   83   
   84           return LookupUtil.getBeanValue(this.pageContext, expressionWithoutScope, scope);
   85   
   86       }
   87   
   88   }