/*
* Copyright 2004 The Apache Software Foundation
*
* 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 javax.servlet.jsp.el;

/**
 * <p>This class is used to customize the way an ExpressionEvaluator resolves
 * variable references at evaluation time.  For example, instances of this class can
 * implement their own variable lookup mechanisms, or introduce the
 * notion of "implicit variables" which override any other variables.
 * An instance of this class should be passed when evaluating
 * an expression.</p>
 *
 * <p>An instance of this class includes the context against which resolution
 * will happen</p>
 *
 * @since 2.0
 */
public interface VariableResolver
{
  //-------------------------------------
  /**
   * Resolves the specified variable.
   * Returns null if the variable is not found.
   * 
   * @param pName the name of the variable to resolve
   * @return the result of the variable resolution
   *
   * @throws ELException if a failure occurred while trying to resolve
   *     the given variable
   **/
  public Object resolveVariable (String pName)
    throws ELException;
					
  //-------------------------------------
}