org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager Maven / Gradle / Ivy
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright 1997-2008 Sun Microsystems, Inc. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can obtain
* a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
* or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
* Sun designates this particular file as subject to the "Classpath" exception
* as provided by Sun in the GPL Version 2 section of the License file that
* accompanied this code. If applicable, add the following below the License
* Header, with the fields enclosed by brackets [] replaced by your own
* identifying information: "Portions Copyrighted [year]
* [name of copyright owner]"
*
* Contributor(s):
*
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*
*
* This file incorporates work covered by the following copyright and
* permission notice:
*
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.taglibs.standard.lang.support;
import java.util.HashMap;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;
import org.apache.taglibs.standard.lang.jstl.Coercions;
import org.apache.taglibs.standard.lang.jstl.ELException;
import org.apache.taglibs.standard.lang.jstl.Logger;
/**
* A conduit to the JSTL EL. Based on...
*
* An implementation of the ExpressionEvaluatorManager called for by
* the JSTL rev1 draft. This class is responsible for delegating a
* request for expression evaluating to the particular, "active"
* ExpressionEvaluator for the given point in the PageContext object
* passed in.
*
* @author Shawn Bayern
*/
public class ExpressionEvaluatorManager {
//*********************************************************************
// Constants
public static final String EVALUATOR_CLASS =
"org.apache.taglibs.standard.lang.jstl.Evaluator";
// private static final String EVALUATOR_PARAMETER =
// "javax.servlet.jsp.jstl.temp.ExpressionEvaluatorClass";
//*********************************************************************
// Internal, static state
private static HashMap nameMap = new HashMap();
private static Logger logger = new Logger(System.out);
//*********************************************************************
// Public static methods
/**
* Invokes the evaluate() method on the "active" ExpressionEvaluator
* for the given pageContext.
*/
public static Object evaluate(String attributeName,
String expression,
Class expectedType,
Tag tag,
PageContext pageContext)
throws JspException
{
// the evaluator we'll use
ExpressionEvaluator target = getEvaluatorByName(EVALUATOR_CLASS);
// delegate the call
return (target.evaluate(
attributeName, expression, expectedType, tag, pageContext));
}
/**
* Invokes the evaluate() method on the "active" ExpressionEvaluator
* for the given pageContext.
*/
public static Object evaluate(String attributeName,
String expression,
Class expectedType,
PageContext pageContext)
throws JspException
{
// the evaluator we'll use
ExpressionEvaluator target = getEvaluatorByName(EVALUATOR_CLASS);
// delegate the call
return (target.evaluate(
attributeName, expression, expectedType, null, pageContext));
}
/**
* Gets an ExpressionEvaluator from the cache, or seeds the cache
* if we haven't seen a particular ExpressionEvaluator before.
*/
public static
ExpressionEvaluator getEvaluatorByName(String name)
throws JspException {
Object oEvaluator = nameMap.get(name);
if (oEvaluator != null) {
return ((ExpressionEvaluator) oEvaluator);
}
try {
synchronized (nameMap) {
oEvaluator = nameMap.get(name);
if (oEvaluator != null) {
return ((ExpressionEvaluator) oEvaluator);
}
ExpressionEvaluator e = (ExpressionEvaluator)
Class.forName(name).newInstance();
nameMap.put(name, e);
return (e);
}
} catch (ClassCastException ex) {
// just to display a better error message
throw new JspException("invalid ExpressionEvaluator: " +
ex.toString(), ex);
} catch (ClassNotFoundException ex) {
throw new JspException("couldn't find ExpressionEvaluator: " +
ex.toString(), ex);
} catch (IllegalAccessException ex) {
throw new JspException("couldn't access ExpressionEvaluator: " +
ex.toString(), ex);
} catch (InstantiationException ex) {
throw new JspException(
"couldn't instantiate ExpressionEvaluator: " +
ex.toString(), ex);
}
}
/** Performs a type conversion according to the EL's rules. */
public static Object coerce(Object value, Class classe)
throws JspException {
try {
// just delegate the call
return Coercions.coerce(value, classe, logger);
} catch (ELException ex) {
throw new JspException(ex);
}
}
}