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     */
017    package org.apache.commons.el;
018    
019    import java.util.List;
020    import java.util.Iterator;
021    import java.util.ArrayList;
022    
023    import javax.servlet.jsp.el.ELException;
024    import javax.servlet.jsp.el.FunctionMapper;
025    import javax.servlet.jsp.el.VariableResolver;
026    
027    /**
028     *
029     * <p>An expression representing a binary operator on a value
030     * 
031     * @author Nathan Abramson - Art Technology Group
032     * @author Shawn Bayern
033     * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: bayard $
034     **/
035    
036    public class BinaryOperatorExpression
037      extends Expression
038    {
039      //-------------------------------------
040      // Properties
041      //-------------------------------------
042      // property expression
043    
044      Expression mExpression;
045      public Expression getExpression ()
046      { return mExpression; }
047      public void setExpression (Expression pExpression)
048      { mExpression = pExpression; }
049    
050      //-------------------------------------
051      // property operators
052    
053      List mOperators;
054      public List getOperators ()
055      { return mOperators; }
056      public void setOperators (List pOperators)
057      { mOperators = pOperators; }
058    
059      //-------------------------------------
060      // property expressions
061    
062      List mExpressions;
063      public List getExpressions ()
064      { return mExpressions; }
065      public void setExpressions (List pExpressions)
066      { mExpressions = pExpressions; }
067    
068      //-------------------------------------
069      /**
070       *
071       * Constructor
072       **/
073      public BinaryOperatorExpression (Expression pExpression,
074                                       List pOperators,
075                                       List pExpressions)
076      {
077        mExpression = pExpression;
078        mOperators = pOperators;
079        mExpressions = pExpressions;
080      }
081    
082      //-------------------------------------
083      // Expression methods
084      //-------------------------------------
085      /**
086       *
087       * Returns the expression in the expression language syntax
088       **/
089      public String getExpressionString ()
090      {
091        StringBuffer buf = new StringBuffer ();
092        buf.append ("(");
093        buf.append (mExpression.getExpressionString ());
094        for (int i = 0, size = mOperators.size(); i < size; i++) {
095          BinaryOperator operator = (BinaryOperator) mOperators.get (i);
096          Expression expression = (Expression) mExpressions.get (i);
097          buf.append (" ");
098          buf.append (operator.getOperatorSymbol ());
099          buf.append (" ");
100          buf.append (expression.getExpressionString ());
101        }
102        buf.append (")");
103    
104        return buf.toString ();
105      }
106    
107      //-------------------------------------
108      /**
109       *
110       * Evaluates to the literal value
111       **/
112      public Object evaluate (VariableResolver pResolver,
113                              FunctionMapper functions)
114        throws ELException
115      {
116        Object value = mExpression.evaluate (pResolver, functions);
117        for (int i = 0, size = mOperators.size(); i < size; i++) {
118          BinaryOperator operator = (BinaryOperator) mOperators.get (i);
119    
120          // For the And/Or operators, we need to coerce to a boolean
121          // before testing if we shouldEvaluate
122          if (operator.shouldCoerceToBoolean ()) {
123            value = Coercions.coerceToBoolean (value);
124          }
125    
126          if (operator.shouldEvaluate (value)) {
127            Expression expression = (Expression) mExpressions.get (i);
128            Object nextValue = expression.evaluate (pResolver,
129                                                    functions);
130    
131            value = operator.apply (value, nextValue);
132          }
133        }
134        return value;
135      }
136    
137        public Expression bindFunctions(final FunctionMapper functions) throws ELException {
138            final List args = new ArrayList(mExpressions.size());
139            for (Iterator argIter = mExpressions.iterator(); argIter.hasNext();) {
140                args.add(((Expression)argIter.next()).bindFunctions(functions));
141            }
142            // it would be nice if we knew for sure that the operators list
143            // was immutable, but we'll just assume so for now.
144            return new BinaryOperatorExpression(
145                    mExpression.bindFunctions(functions),
146                    mOperators,
147                    args);
148        }
149    
150      //-------------------------------------
151    }