/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
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 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
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 * Portions Copyright Apache Software Foundation.
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 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
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 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
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package org.apache.taglibs.standard.lang.jstl;

import javax.servlet.jsp.PageContext;

/**
 *
 * <p>This is the JSTL-specific implementation of VariableResolver.
 * It looks up variable references in the PageContext, and also
 * recognizes references to implicit objects.
 * 
 * @author Nathan Abramson - Art Technology Group
 * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: tcfujii $
 **/

public class JSTLVariableResolver
  implements VariableResolver
{
  //-------------------------------------
  /**
   *
   * Resolves the specified variable within the given context.
   * Returns null if the variable is not found.
   **/
  public Object resolveVariable (String pName,
				 Object pContext)
    throws ELException
  {
    PageContext ctx = (PageContext) pContext;

    // Check for implicit objects
    if ("pageContext".equals (pName)) {
      return ctx;
    }
    else if ("pageScope".equals (pName)) {
      return ImplicitObjects.
	getImplicitObjects (ctx).
	getPageScopeMap ();
    }
    else if ("requestScope".equals (pName)) {
      return ImplicitObjects.
	getImplicitObjects (ctx).
	getRequestScopeMap ();
    }
    else if ("sessionScope".equals (pName)) {
      return ImplicitObjects.
	getImplicitObjects (ctx).
	getSessionScopeMap ();
    }
    else if ("applicationScope".equals (pName)) {
      return ImplicitObjects.
	getImplicitObjects (ctx).
	getApplicationScopeMap ();
    }
    else if ("param".equals (pName)) {
      return ImplicitObjects.
	getImplicitObjects (ctx).
	getParamMap ();
    }
    else if ("paramValues".equals (pName)) {
      return ImplicitObjects.
	getImplicitObjects (ctx).
	getParamsMap ();
    }
    else if ("header".equals (pName)) {
      return ImplicitObjects.
	getImplicitObjects (ctx).
	getHeaderMap ();
    }
    else if ("headerValues".equals (pName)) {
      return ImplicitObjects.
	getImplicitObjects (ctx).
	getHeadersMap ();
    }
    else if ("initParam".equals (pName)) {
      return ImplicitObjects.
	getImplicitObjects (ctx).
	getInitParamMap ();
    }
    else if ("cookie".equals (pName)) {
      return ImplicitObjects.
	getImplicitObjects (ctx).
	getCookieMap ();
    }

    // Otherwise, just look it up in the page context
    else {
      return ctx.findAttribute (pName);
    }
  }
					
  //-------------------------------------
}