/*
* Copyright 2011 <a href="mailto:lincolnbaxter@gmail.com">Lincoln Baxter, III</a>
*
* 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.ocpsoft.rewrite.faces;
import javax.el.ELContext;
import javax.el.ExpressionFactory;
import javax.el.MethodExpression;
import javax.el.ValueExpression;
import javax.faces.context.FacesContext;
import org.ocpsoft.rewrite.el.spi.ExpressionLanguageProvider;
/**
* Implementation of {@link ExpressionLanguageProvider} that uses the {@link FacesContext} to obtain the
* {@link ELContext} and the {@link ExpressionFactory}.
*
* @author Christian Kaltepoth
*/
public class FacesExpressionLanguageProvider implements ExpressionLanguageProvider
{
@Override
public int priority()
{
return 30;
}
@Override
public Object retrieveValue(String expression) throws UnsupportedOperationException
{
FacesContext facesContext = getFacesContext();
ELContext elContext = facesContext.getELContext();
return getValueExpression(facesContext, expression).getValue(elContext);
}
@Override
public void submitValue(String expression, Object value) throws UnsupportedOperationException
{
FacesContext facesContext = getFacesContext();
ELContext elContext = facesContext.getELContext();
ValueExpression valueExpression = getValueExpression(facesContext, expression);
Class<?> referencedType = valueExpression.getType(elContext);
// the value that will be injected
Object toInject = null;
// the expression is referencing an array
if (referencedType.isArray()) {
// ensure the value that will be injected is an array
if (value != null && !value.getClass().isArray()) {
toInject = new Object[] { value };
}
else {
toInject = value;
}
}
// expression is not referencing an array
else {
// if value to inject is an array, just use the first element
if (value != null && value.getClass().isArray()) {
Object[] valueAsArray = (Object[]) value;
if (valueAsArray.length > 0) {
toInject = valueAsArray[0];
}
else {
toInject = null;
}
}
// simple case: neither the expression is referencing an array nor the value is one
else {
toInject = value;
}
}
// set the value
Object coercedValue = facesContext.getApplication().getExpressionFactory().coerceToType(toInject, referencedType);
valueExpression.setValue(elContext, coercedValue);
}
@Override
public Object evaluateMethodExpression(String expression) throws UnsupportedOperationException
{
return evaluateMethodExpression(expression, new Object[0]);
}
@Override
public Object evaluateMethodExpression(String expression, Object... values) throws UnsupportedOperationException
{
String el = toELExpression(expression);
FacesContext facesContext = getFacesContext();
ELContext elContext = facesContext.getELContext();
ExpressionFactory expressionFactory = facesContext.getApplication().getExpressionFactory();
MethodExpression methodExpression = expressionFactory.createMethodExpression(elContext, el,
Object.class, new Class[values.length]);
return methodExpression.invoke(elContext, values);
}
/**
* Creates an {@link ValueExpression} for the supplied EL expression
*/
private ValueExpression getValueExpression(FacesContext facesContext, String expression)
{
String el = toELExpression(expression);
ExpressionFactory expressionFactory = facesContext.getApplication().getExpressionFactory();
return expressionFactory.createValueExpression(facesContext.getELContext(), el, Object.class);
}
/**
* Obtains the {@link FacesContext} using {@link FacesContext#getCurrentInstance()}. This method will throw an
* {@link IllegalArgumentException} if the {@link FacesContext} is not available.
*/
private FacesContext getFacesContext()
{
FacesContext facesContext = FacesContext.getCurrentInstance();
if (facesContext == null) {
throw new IllegalArgumentException(
"FacesContext.getCurrentInstance() returned null. EL expressions can only be evaluated in the JSF lifecycle. "
+ "You should use PhaseAction and PhaseBinding to perform a deferred operation instead.");
}
return facesContext;
}
/**
* Adds #{..} to the expression if required
*/
private String toELExpression(String s)
{
if (s != null && !s.startsWith("#{")) {
return "#{" + s + "}";
}
return s;
}
}