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    1   /*
    2    * Copyright 2002,2004 The Apache Software Foundation.
    3    *
    4    * Licensed under the Apache License, Version 2.0 (the "License");
    5    * you may not use this file except in compliance with the License.
    6    * You may obtain a copy of the License at
    7    *
    8    *      http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  package org.apache.commons.jelly.expression;
    17
    18  import java.util.Collections;
    19  import java.util.Collection;
    20  import java.util.Enumeration;
    21  import java.util.Iterator;
    22  import java.util.List;
    23  import java.util.Map;
    24
    25  import org.apache.commons.collections.iterators.ArrayIterator;
    26  import org.apache.commons.collections.iterators.EnumerationIterator;
    27  import org.apache.commons.collections.iterators.SingletonIterator;
    28
    29  import org.apache.commons.jelly.JellyContext;
    30  import org.apache.commons.lang.StringUtils;
    31
    32  /*** <p><code>ExpressionSupport</code>
    33    * an abstract base class for Expression implementations
    34    * which provides default implementations of some of the
    35    * typesafe evaluation methods.</p>
    36    *
    37    * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
    38    * @version $Revision: 155420 $
    39    */
    40  public abstract class ExpressionSupport implements Expression {
    41
    42      protected static final Iterator EMPTY_ITERATOR = Collections.EMPTY_LIST.iterator();
    43
    44      // inherit javadoc from interface
    45      public String evaluateAsString(JellyContext context) {
    46          Object value = evaluateRecurse(context);
    47          // sometimes when Jelly is used inside Maven the value
    48          // of an expression can actually be an expression.
    49          // e.g. ${foo.bar} can lookup "foo.bar" in a Maven context
    50          // which could actually be an expression
    51
    52          if ( value != null ) {
    53              return value.toString();
    54          }
    55          return null;
    56      }
    57
    58
    59      // inherit javadoc from interface
    60      public Object evaluateRecurse(JellyContext context) {
    61          Object value = evaluate(context);
    62          if (value instanceof Expression) {
    63              Expression expression = (Expression) value;
    64              return expression.evaluateRecurse(context);
    65          }
    66          return value;
    67      }
    68
    69      // inherit javadoc from interface
    70      public boolean evaluateAsBoolean(JellyContext context) {
    71          Object value = evaluateRecurse(context);
    72          if ( value instanceof Boolean ) {
    73              Boolean b = (Boolean) value;
    74              return b.booleanValue();
    75          }
    76          else if ( value instanceof String ) {
    77              // return Boolean.getBoolean( (String) value );
    78              String str = (String) value;
    79
    80              return ( str.equalsIgnoreCase( "on" )
    81                   ||
    82                   str.equalsIgnoreCase( "yes" )
    83                   ||
    84                   str.equals( "1" )
    85                   ||
    86                   str.equalsIgnoreCase( "true" ) );
    87
    88          }
    89          return false;
    90      }
    91
    92      // inherit javadoc from interface
    93      public Iterator evaluateAsIterator(JellyContext context) {
    94          Object value = evaluateRecurse(context);
    95          if ( value == null ) {
    96              return EMPTY_ITERATOR;
    97          } else if ( value instanceof Iterator ) {
    98              return (Iterator) value;
    99          } else if ( value instanceof List ) {
    100             List list = (List) value;
    101             return list.iterator();
    102         } else if ( value instanceof Map ) {
    103             Map map = (Map) value;
    104             return map.entrySet().iterator();
    105         } else if ( value.getClass().isArray() ) {
    106             return new ArrayIterator( value );
    107         } else if ( value instanceof Enumeration ) {
    108             return new EnumerationIterator((Enumeration ) value);
    109         } else if ( value instanceof Collection ) {
    110           Collection collection = (Collection) value;
    111           return collection.iterator();
    112         } else if ( value instanceof String ) {
    113            String[] array = StringUtils.split((String) value, "," );
    114            array = StringUtils.stripAll( array );
    115            return new ArrayIterator( array );
    116         } else {
    117             // XXX: should we return single iterator?
    118             return new SingletonIterator( value );
    119         }
    120     }
    121 }