/*
* JBoss, Home of Professional Open Source
* Copyright 2011, Red Hat, Inc., and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* 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.jboss.seam.faces.component;
import java.beans.FeatureDescriptor;
import java.util.Iterator;
import java.util.Locale;
import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ELResolver;
import javax.el.FunctionMapper;
import javax.el.ValueExpression;
import javax.el.ValueReference;
import javax.el.VariableMapper;
import javax.faces.el.CompositeComponentExpressionHolder;
/**
* <p>
* Analyzes a {@link ValueExpression} and provides access to the base object and property name referenced by the expression.
* </p>
* <p/>
* <p>
* The getValueReference(ELContext) method returns a {@link ValueReference} object, which encapsulates the base object and
* property name to which the expression maps. This process works by resolving the expression up until the last segment.
* </p>
* <p/>
* <p>
* Although access to the ValueReference was added in EL 2.2, the feature does not work correctly, which is why this custom
* class is required.
* </p>
*
* @author Dan Allen
*/
class ValueExpressionAnalyzer {
private ValueExpression expression;
public ValueExpressionAnalyzer(ValueExpression expression) {
this.expression = expression;
}
public ValueReference getValueReference(ELContext elContext) {
InterceptingResolver resolver = new InterceptingResolver(elContext.getELResolver());
try {
expression.setValue(decorateELContext(elContext, resolver), null);
} catch (ELException ele) {
return null;
}
ValueReference reference = resolver.getValueReference();
if (reference != null) {
Object base = reference.getBase();
if (base instanceof CompositeComponentExpressionHolder) {
ValueExpression ve = ((CompositeComponentExpressionHolder) base)
.getExpression((String) reference.getProperty());
if (ve != null) {
this.expression = ve;
reference = getValueReference(elContext);
}
}
}
return reference;
}
private ELContext decorateELContext(final ELContext context, final ELResolver resolver) {
return new ELContext() {
// punch in our new ELResolver
@Override
public ELResolver getELResolver() {
return resolver;
}
// The rest of the methods simply delegate to the existing context
@Override
public Object getContext(Class key) {
return context.getContext(key);
}
@Override
public Locale getLocale() {
return context.getLocale();
}
@Override
public boolean isPropertyResolved() {
return context.isPropertyResolved();
}
@Override
public void putContext(Class key, Object contextObject) {
context.putContext(key, contextObject);
}
@Override
public void setLocale(Locale locale) {
context.setLocale(locale);
}
@Override
public void setPropertyResolved(boolean resolved) {
context.setPropertyResolved(resolved);
}
@Override
public FunctionMapper getFunctionMapper() {
return context.getFunctionMapper();
}
@Override
public VariableMapper getVariableMapper() {
return context.getVariableMapper();
}
};
}
private static class InterceptingResolver extends ELResolver {
private ELResolver delegate;
private ValueReference valueReference;
public InterceptingResolver(ELResolver delegate) {
this.delegate = delegate;
}
public ValueReference getValueReference() {
return valueReference;
}
// Capture the base and property rather than write the value
@Override
public void setValue(ELContext context, Object base, Object property, Object value) {
if (base != null && property != null) {
context.setPropertyResolved(true);
valueReference = new ValueReference(base, property.toString());
}
}
// The rest of the methods simply delegate to the existing context
@Override
public Object getValue(ELContext context, Object base, Object property) {
return delegate.getValue(context, base, property);
}
@Override
public Class<?> getType(ELContext context, Object base, Object property) {
return delegate.getType(context, base, property);
}
@Override
public boolean isReadOnly(ELContext context, Object base, Object property) {
return delegate.isReadOnly(context, base, property);
}
@Override
public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) {
return delegate.getFeatureDescriptors(context, base);
}
@Override
public Class<?> getCommonPropertyType(ELContext context, Object base) {
return delegate.getCommonPropertyType(context, base);
}
}
}