/** * Licensed under the Artistic License; you may not use this file * except in compliance with the License. * You may obtain a copy of the License at * *      http://displaytag.sourceforge.net/license.html * * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. */package org.displaytag.tags.el;import javax.servlet.jsp.JspException;import javax.servlet.jsp.PageContext;import javax.servlet.jsp.tagext.Tag;import org.apache.commons.lang.BooleanUtils;import org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager;/** * Utility class to help with the evaluation of JSTL Expression Language. It mainly encapsulates the calls to * ExpressionEvaluationManager to ease the use of this class. * @author Tim McCune * @author Fabrizio Giustina * @version $Revision: 1081 $ ($Author: fgiust $) */public class ExpressionEvaluator{    /**     * page context.     */    private PageContext pageContext;    /**     * tag.     */    private Tag tag;    /**     * Creates a new ExpressionEvaluator for the given tag and pagecontext.     * @param sourceTag tag where the expression has to be evaluated     * @param context the page context     */    public ExpressionEvaluator(Tag sourceTag, PageContext context)    {        this.tag = sourceTag;        this.pageContext = context;    }    /**     * Evaluate expression in attrValue.     * @param attrName attribute name     * @param attrValue attribute value     * @return evaluate expression of attrValue, null if attrValue is null.     * @param returnClass class the returned object is instance of     * @throws JspException exception thrown by ExpressionEvaluatorManager     */    public Object eval(String attrName, String attrValue, Class returnClass) throws JspException    {        return attrValue != null ? ExpressionEvaluatorManager.evaluate(            attrName,            attrValue,            returnClass,            this.tag,            this.pageContext) : null;    }    /**     * Evaluate expression in attrValueas as a String.     * @param attrName attribute name     * @param attrValue attribute value     * @return evaluate expression of attrValue, null if attrValue is null.     * @throws JspException exception thrown by ExpressionEvaluatorManager     */    public String evalString(String attrName, String attrValue) throws JspException    {        return (String) eval(attrName, attrValue, String.class);    }    /**     * Evaluate expression in attrValueas as a boolean.     * @param attrName attribute name     * @param attrValue attribute value     * @return evaluate expression of attrValue, false if attrValue is null.     * @throws JspException exception thrown by ExpressionEvaluatorManager     */    public boolean evalBoolean(String attrName, String attrValue) throws JspException    {        return BooleanUtils.toBoolean((Boolean) eval(attrName, attrValue, Boolean.class));    }    /**     * Evaluate expression in attrValueas as a long.     * @param attrName attribute name     * @param attrValue attribute value     * @return evaluate expression of attrValue, -1 if attrValue is null.     * @throws JspException exception thrown by ExpressionEvaluatorManager     */    public long evalLong(String attrName, String attrValue) throws JspException    {        Long rtn = (Long) eval(attrName, attrValue, Long.class);        if (rtn != null)        {            return rtn.longValue();        }        return -1L;    }    /**     * Evaluate expression in attrValueas as a int.     * @param attrName attribute name     * @param attrValue attribute value     * @return evaluate expression of attrValue, -1 if attrValue is null.     * @throws JspException exception thrown by ExpressionEvaluatorManager     */    public int evalInt(String attrName, String attrValue) throws JspException    {        Integer rtn = (Integer) eval(attrName, attrValue, Integer.class);        if (rtn != null)        {            return rtn.intValue();        }        return -1;    }}