/*
* ====================================================================
*
* Frame2 Open Source License
*
* Copyright (c) 2004-2007 Megatome Technologies. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by
* Megatome Technologies."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Frame2 Project", and "Frame2",
* must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact iamthechad@sourceforge.net.
*
* 5. Products derived from this software may not be called "Frame2"
* nor may "Frame2" appear in their names without prior written
* permission of Megatome Technologies.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL MEGATOME TECHNOLOGIES OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*/
package org.megatome.frame2.tagsupport.util;
import java.util.MissingResourceException;
import java.util.ResourceBundle;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;
import org.apache.taglibs.standard.tag.common.core.NullAttributeException;
import org.apache.taglibs.standard.tag.el.core.ExpressionUtil;
import org.megatome.frame2.util.ResourceLocator;
/**
* The EvalHelper provides services for evaluating attributes set in the Frame2 tags. This is the
* class that is responsible for EL attribute evaluation.
*/
public final class EvalHelper {
// DOC: document the conventions and rules for referencing a resource key (vice expression)
private final static String RESOURCE_PREFIX = "%{"; //$NON-NLS-1$
private final static char RESOURCE_SUFFIX = '}';
private EvalHelper() {
// not public
}
/**
* Evaluate the attribute value and return the result of the expression. The expression may be
* of three types:<br>
* <br>
* 1) String literal, in which case the expression will return the attribute value.<br>
* 2) Expression language (EL) expression, in which case the expression will be evaluated
* per the language. Expressions are denoted through the dollar-sign and bracket convention
* of <code>${foo.bar}</code><br>
* 3) Resource key, in which case the expression will return the corresponding value from the
* configured resource bundle. Resource keys are denoted using a Frame2 convention of
* percent-sign and brackets, e.g. <code>%{foo.bar}</code>.
* @param tagName name of the tag
* @param attrName name of the attribute
* @param attrValue value of the attribute. This parameter must following the conventions indicated
* above to be properly evaluated
* @param attrType type of the attribute
* @param tagObject source tag for the attribute
* @param pageContext page context
* @return Object result of the expression
* @throws JspException
* @throws NullAttributeException thrown if no result is located.
*/
public static Object eval(
String tagName,
String attrName,
String attrValue,
Class<?> attrType,
Tag tagObject,
PageContext pageContext)
throws JspException, NullAttributeException {
Object result = null;
if (isResourceKey(attrValue)) {
result = getResource(attrValue, pageContext);
} else {
result =
ExpressionUtil.evalNotNull(
tagName,
attrName,
attrValue,
attrType,
tagObject,
pageContext);
}
if (result == null) {
throw new NullAttributeException(attrName, tagName);
}
return result;
}
private static Object getResource(String attrValue, PageContext pageContext)
throws JspException {
Object result = null;
ResourceBundle bundle =
ResourceLocator.getBundle(HTMLHelpers.getLocale(pageContext, null));
String key = attrValue.substring(2, attrValue.length() - 1);
try {
if (bundle != null) {
result = bundle.getObject(key);
}
} catch (MissingResourceException e) {
throw new JspException("Unable to load resource for key " + key, e); //$NON-NLS-1$
}
return result;
}
private static boolean isResourceKey(String value) {
boolean result = false;
if (value != null && value.indexOf(RESOURCE_PREFIX) == 0) {
result = value.charAt(value.length() - 1) == RESOURCE_SUFFIX;
}
return result;
}
}