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 javax.servlet.jsp.el.ELException;
020    import javax.servlet.jsp.el.FunctionMapper;
021    import javax.servlet.jsp.el.VariableResolver;
022    
023    /**
024     *
025     * <p>Represents an expression String consisting of a mixture of
026     * Strings and Expressions.
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    
033    public class ExpressionString extends Expression
034    {
035      //-------------------------------------
036      // Properties
037      //-------------------------------------
038      // property elements
039    
040      Object [] mElements;
041      public Object [] getElements ()
042      { return mElements; }
043      public void setElements (Object [] pElements)
044      { mElements = pElements; }
045    
046      //-------------------------------------
047      /**
048       *
049       * Constructor
050       **/
051      public ExpressionString (Object [] pElements)
052      {
053        mElements = pElements;
054      }
055    
056      //-------------------------------------
057      /**
058       *
059       * Evaluates the expression string by evaluating each element,
060       * converting it to a String (using toString, or "" for null values)
061       * and concatenating the results into a single String.
062       **/
063      public Object evaluate (VariableResolver pResolver,
064                              FunctionMapper functions)
065        throws ELException
066      {
067        StringBuffer buf = new StringBuffer ();
068        for (int i = 0; i < mElements.length; i++) {
069          Object elem = mElements [i];
070          if (elem instanceof String) {
071            buf.append ((String) elem);
072          }
073          else if (elem instanceof Expression) {
074            Object val = 
075              ((Expression) elem).evaluate (pResolver, functions);
076            if (val != null) {
077              buf.append (val.toString ());
078            }
079          }
080        }
081        return buf.toString ();
082      }
083    
084      //-------------------------------------
085      /**
086       *
087       * Returns the expression in the expression language syntax
088       **/
089      public String getExpressionString ()
090      {
091        StringBuffer buf = new StringBuffer ();
092        for (int i = 0; i < mElements.length; i++) {
093          Object elem = mElements [i];
094          if (elem instanceof String) {
095            buf.append ((String) elem);
096          }
097          else if (elem instanceof Expression) {
098            buf.append ("${");
099            buf.append (((Expression) elem).getExpressionString ());
100            buf.append ("}");
101          }
102        }
103        return buf.toString ();
104      }
105    
106      //-------------------------------------
107    
108      public Expression bindFunctions(FunctionMapper functions) throws ELException {
109          final Object[] boundElements = new Object[mElements.length];
110          for (int i = 0; i < mElements.length; i++) {
111              if (mElements[i] instanceof Expression) {
112                  boundElements[i] = ((Expression)mElements[i]).bindFunctions(functions);
113              } else {
114                  boundElements[i] = mElements[i];
115              }
116          }
117          return new ExpressionString(boundElements);
118      }
119    }