001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.el;
018
019import javax.servlet.jsp.el.ELException;
020import javax.servlet.jsp.el.FunctionMapper;
021import javax.servlet.jsp.el.VariableResolver;
022
023/**
024 *
025 * <p>The abstract class from which all expression types
026 * derive.
027 * 
028 * @author Nathan Abramson - Art Technology Group
029 * @author Shawn Bayern
030 * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: bayard $
031 **/
032
033public abstract class Expression
034{
035  //-------------------------------------
036  // Member variables
037  //-------------------------------------
038
039  //-------------------------------------
040  /**
041   *
042   * Returns the expression in the expression language syntax
043   **/
044  public abstract String getExpressionString ();
045
046  //-------------------------------------
047  /**
048   *
049   * Evaluates the expression in the given context
050   **/
051  public abstract Object evaluate (VariableResolver pResolver, FunctionMapper functions)
052    throws ELException;
053
054  //-------------------------------------
055
056  /**
057   * Returns an expression with all <code>FunctionInvocation</code>s replaced by
058   * <code>BoundFunctionInvocation</code>s.
059   * @param functions the functions to use in this transformation
060   * @return an Expression identical to this expression except with all
061   *    <code>FunctionInvocation</code>s replaced by
062   *    <code>BoundFunctionInvocation</code>s.
063   * @throws ELException if any of the functions in this <code>Expression</code> are
064   *    not present in <code>functions</code>
065   */
066  public abstract Expression bindFunctions(FunctionMapper functions)
067      throws ELException;
068
069}