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Private implementation of the Apache MyFaces Trinidad project
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/*
 *  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.trinidadinternal.el;

import java.beans.FeatureDescriptor;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;

import java.util.List;
import java.util.Map;

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

import org.apache.myfaces.trinidad.context.RequestContext;

/**
 * ELResolver implementation for Trinidad.  Serves up:
 * 
 *   requestContext: the RequestContext instance
 *   pageFlowScope: the page flow scope Map
 *   processScope: a backwards compatibility alias for page flow scope
 * 
 */
public class TrinidadELResolver
  extends ELResolver
{
  /**
   * EL variable name for page-flow scope
   */
  static public final String PAGE_FLOW_SCOPE_VARIABLE_NAME = "pageFlowScope";

  public TrinidadELResolver()
  {
  }

  public Object getValue(ELContext elContext, Object base, 
                         Object property)
  {
    if (base == null)
    {
      if (RequestContext.VARIABLE_NAME.equals(property))
      {
        elContext.setPropertyResolved(true);
        return RequestContext.getCurrentInstance();
      }
      // Support both "pageFlowScope" and "processScope"
      // as EL variables to give developers a time to migrate
      else if (PAGE_FLOW_SCOPE_VARIABLE_NAME.equals(property) ||
             "processScope".equals(property))
      {
        elContext.setPropertyResolved(true);
        return RequestContext.getCurrentInstance().getPageFlowScope();
      }
    }
    
    return null;
  }

  public Class getType(ELContext elContext, Object base, 
                          Object property)
  {
    if (base == null)
    {
      if (RequestContext.VARIABLE_NAME.equals(property))
      {
        elContext.setPropertyResolved(true);
        return RequestContext.class;
      }
      // Support both "pageFlowScope" and "processScope"
      // as EL variables to give developers a time to migrate
      else if (PAGE_FLOW_SCOPE_VARIABLE_NAME.equals(property) ||
             "processScope".equals(property))
      {
        elContext.setPropertyResolved(true);
        return Map.class;
      }
    }
    
    return null;
  }

  public void setValue(ELContext elContext, Object base, Object property, 
                       Object value)
  {
    if (PAGE_FLOW_SCOPE_VARIABLE_NAME.equals(base) ||
        "processScope".equals(base))
    {
      Map m = RequestContext.getCurrentInstance().getPageFlowScope();
      m.put(property, value);
      elContext.setPropertyResolved(true);
    }
  }

  public boolean isReadOnly(ELContext elContext, Object base, 
                            Object property)
  {
    return false;
  }

  public Iterator getFeatureDescriptors(ELContext elContext, 
                                                           Object base)
  {
    if (base == null)
    {
      if (_featureDescriptorList == null)
        _featureDescriptorList = _createFeatureDescriptorList();
      return _featureDescriptorList.iterator();
    }
    
    return null;
  }

  public Class getCommonPropertyType(ELContext elContext, Object base)
  {
    if (base == null)
      return String.class;
    
    return null;
  }

  /**
   * Creates the list of FeatureDescriptors.
   */
  private List _createFeatureDescriptorList()
  {
    ArrayList list = new ArrayList();
    // FeatureDescriptor for "requestContext"
    FeatureDescriptor requestContext = new FeatureDescriptor();
    requestContext.setName(RequestContext.VARIABLE_NAME);
    // TODO translate this
    requestContext.setShortDescription("Trinidad RequestContext");
    requestContext.setValue(ELResolver.RESOLVABLE_AT_DESIGN_TIME, false);
    requestContext.setValue(ELResolver.TYPE, RequestContext.class);
    list.add(requestContext);
    
    // FeatureDescriptor for "pageFlowScope"
    FeatureDescriptor pageFlowScope = new FeatureDescriptor();
    pageFlowScope.setName(PAGE_FLOW_SCOPE_VARIABLE_NAME);
    // TODO translate this
    pageFlowScope.setShortDescription("Trinidad Page Flow Scope");
    pageFlowScope.setValue(ELResolver.RESOLVABLE_AT_DESIGN_TIME, false);
    pageFlowScope.setValue(ELResolver.TYPE, Map.class);
    list.add(pageFlowScope);
    
    // FeatureDescriptor for "processScope"
    FeatureDescriptor processScope = new FeatureDescriptor();
    processScope.setName(PAGE_FLOW_SCOPE_VARIABLE_NAME);
    // TODO translate this
    pageFlowScope.setShortDescription(
      "Backwards compatibility alias for Trinidad Page Flow Scope");
    processScope.setExpert(true);
    processScope.setValue(ELResolver.RESOLVABLE_AT_DESIGN_TIME, false);
    processScope.setValue(ELResolver.TYPE, Map.class);
    list.add(pageFlowScope);

    return Collections.unmodifiableList(list);
  }

  private List _featureDescriptorList;
}