/*
* Copyright 2002,2004 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.commons.jelly.expression.jexl;
import java.util.Map;
import java.util.Set;
import java.util.Collection;
import org.apache.commons.jelly.JellyContext;
import org.apache.commons.jelly.expression.ExpressionSupport;
import org.apache.commons.jexl.Expression;
import org.apache.commons.jexl.JexlContext;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* Represents a <a href="http://jakarta.apache.org/commons/jexl.html">Jexl</a>
* expression which fully supports the Expression Language in JSTL and JSP
* along with some extra features like object method invocation.
*
* @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
* @version $Revision: 1.18 $
*/
public class JexlExpression extends ExpressionSupport {
/** The Log to which logging calls will be made. */
private static final Log log = LogFactory.getLog(JexlExpression.class);
/** The Jexl expression object */
private Expression expression;
public JexlExpression(Expression expression) {
this.expression = expression;
}
public String toString() {
return super.toString() + "[" + expression.getExpression() + "]";
}
// Expression interface
//-------------------------------------------------------------------------
public String getExpressionText() {
return "${" + expression.getExpression() + "}";
}
public Object evaluate(JellyContext context) {
try {
JexlContext jexlContext = new JellyJexlContext( context );
if (log.isDebugEnabled()) {
log.debug("Evaluating EL: " + expression.getExpression());
}
Object value = expression.evaluate(jexlContext);
if (log.isDebugEnabled()) {
log.debug("value of expression: " + value);
}
return value;
}
catch (Exception e) {
log.warn("Caught exception evaluating: " + expression + ". Reason: " + e, e);
return null;
}
}
}
class JellyJexlContext implements JexlContext {
private Map vars;
JellyJexlContext(JellyContext context) {
this.vars = new JellyMap( context );
}
public void setVars(Map vars) {
this.vars.clear();
this.vars.putAll( vars );
}
public Map getVars() {
return this.vars;
}
}
class JellyMap implements Map {
private JellyContext context;
JellyMap(JellyContext context) {
this.context = context;
}
public Object get(Object key) {
return context.getVariable( (String) key );
}
public void clear() {
// not implemented
}
public boolean containsKey(Object key) {
return ( get( key ) != null );
}
public boolean containsValue(Object value) {
return false;
}
public Set entrySet() {
return null;
}
public boolean isEmpty() {
return false;
}
public Set keySet() {
return null;
}
public Object put(Object key, Object value) {
return null;
}
public void putAll(Map t) {
// not implemented
}
public Object remove(Object key) {
return null;
}
public int size() {
return -1;
}
public Collection values() {
return null;
}
}