/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.myfaces.view.facelets.el;

import javax.el.ValueExpression;
import javax.el.VariableMapper;

/**
 * Composite VariableMapper that attempts to load the ValueExpression from the first VariableMapper, then the second if
 * <code>null</code>.
 * 
 * @see javax.el.VariableMapper
 * @see javax.el.ValueExpression
 * 
 * @author Jacob Hookom
 * @version $Id$
 */
public final class CompositeVariableMapper extends VariableMapper
{

    private final VariableMapper var0;
    private final VariableMapper var1;

    public CompositeVariableMapper(VariableMapper var0, VariableMapper var1)
    {
        this.var0 = var0;
        this.var1 = var1;
    }

    /**
     * @see javax.el.VariableMapper#resolveVariable(java.lang.String)
     */
    @Override
    public ValueExpression resolveVariable(String name)
    {
        ValueExpression ve = this.var0.resolveVariable(name);
        if (ve == null)
        {
            return this.var1.resolveVariable(name);
        }
        return ve;
    }

    /**
     * @see javax.el.VariableMapper#setVariable(java.lang.String, javax.el.ValueExpression)
     */
    @Override
    public ValueExpression setVariable(String name, ValueExpression expression)
    {
        return this.var0.setVariable(name, expression);
    }

}