tiles-el/src/main/java/org/apache/tiles/el/TilesContextELResolver.java

/*
 * $Id$
 *
 * 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.tiles.el;

import java.beans.FeatureDescriptor;
import java.util.Iterator;

import javax.el.ELContext;
import javax.el.ELResolver;

import org.apache.tiles.request.ApplicationContext;
import org.apache.tiles.request.Request;
import org.apache.tiles.util.CombinedBeanInfo;

/**
 * Resolves properties of {@link Request} and
 * {@link ApplicationContext}.
 *
 * @version $Rev$ $Date$
 * @since 2.2.1
 */
public class TilesContextELResolver extends ELResolver {

    /**
     * Internal bean resolver to resolve beans in any context.
     */
    private ELResolver beanElResolver;

    /**
     * Constructor.
     *
     * @param beanElResolver The used bean resolver.
     */
    public TilesContextELResolver(ELResolver beanElResolver) {
        this.beanElResolver = beanElResolver;
    }

    /**
     * The beaninfos about {@link Request} and {@link ApplicationContext}.
     */
    private CombinedBeanInfo requestBeanInfo = new CombinedBeanInfo(
            Request.class, ApplicationContext.class);

    /** {@inheritDoc} */
    @Override
    public Class<?> getCommonPropertyType(ELContext context, Object base) {
        // only resolve at the root of the context
        if (base != null) {
            return null;
        }

        return String.class;
    }

    /** {@inheritDoc} */
    @Override
    public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context,
            Object base) {
        // only resolve at the root of the context
        if (base != null) {
            return null;
        }

        return requestBeanInfo.getDescriptors().iterator();
    }

    /** {@inheritDoc} */
    @Override
    public Class<?> getType(ELContext context, Object base, Object property) {
        // only resolve at the root of the context
        if (base != null) {
            return null;
        }

        Class<?> retValue = null;
        if (requestBeanInfo.getProperties(Request.class).contains(property)) {
            Request request = (Request) context
                    .getContext(Request.class);
            retValue = beanElResolver.getType(context, request, property);
        } else if (requestBeanInfo.getProperties(ApplicationContext.class).contains(property)) {
            ApplicationContext applicationContext = (ApplicationContext) context
                    .getContext(ApplicationContext.class);
            retValue = beanElResolver.getType(context, applicationContext, property);
        }

        if (retValue != null) {
            context.setPropertyResolved(true);
        }

        return retValue;
    }

    /** {@inheritDoc} */
    @Override
    public Object getValue(ELContext context, Object base, Object property) {
        // only resolve at the root of the context
        if (base != null) {
            return null;
        }

        Object retValue = null;

        if (requestBeanInfo.getProperties(Request.class).contains(property)) {
            Request request = (Request) context
                    .getContext(Request.class);
            retValue = beanElResolver.getValue(context, request, property);
        } else if (requestBeanInfo.getProperties(ApplicationContext.class)
                .contains(property)) {
            ApplicationContext applicationContext = (ApplicationContext) context
                    .getContext(ApplicationContext.class);
            retValue = beanElResolver.getValue(context, applicationContext, property);
        }

        if (retValue != null) {
            context.setPropertyResolved(true);
        }

        return retValue;
    }

    /** {@inheritDoc} */
    @Override
    public boolean isReadOnly(ELContext context, Object base, Object property) {
        if (context == null) {
            throw new NullPointerException();
        }

        return true;
    }

    /** {@inheritDoc} */
    @Override
    public void setValue(ELContext context, Object base, Object property,
            Object value) {
        // Does nothing for the moment.
    }
}