View Javadoc

    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
    17  package org.apache.commons.jelly.expression.jexl;
    18
    19  import java.util.Map;
    20  import java.util.Set;
    21  import java.util.Collection;
    22
    23  import org.apache.commons.jelly.JellyContext;
    24  import org.apache.commons.jelly.expression.ExpressionSupport;
    25
    26  import org.apache.commons.jexl.Expression;
    27  import org.apache.commons.jexl.JexlContext;
    28
    29  import org.apache.commons.logging.Log;
    30  import org.apache.commons.logging.LogFactory;
    31
    32  /***
    33   * Represents a <a href="http://jakarta.apache.org/commons/jexl.html">Jexl</a>
    34   * expression which fully supports the Expression Language in JSTL and JSP
    35   * along with some extra features like object method invocation.
    36   *
    37   * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
    38   * @version $Revision: 155420 $
    39   */
    40
    41  public class JexlExpression extends ExpressionSupport {
    42
    43      /*** The Log to which logging calls will be made. */
    44      private static final Log log = LogFactory.getLog(JexlExpression.class);
    45
    46      /*** The Jexl expression object */
    47      private Expression expression;
    48
    49      public JexlExpression(Expression expression) {
    50          this.expression = expression;
    51      }
    52
    53      public String toString() {
    54          return super.toString() + "[" + expression.getExpression() + "]";
    55      }
    56
    57      // Expression interface
    58      //-------------------------------------------------------------------------
    59      public String getExpressionText() {
    60          return "${" + expression.getExpression() + "}";
    61      }
    62
    63      public Object evaluate(JellyContext context) {
    64          try {
    65              JexlContext jexlContext = new JellyJexlContext( context );
    66              if (log.isDebugEnabled()) {
    67                  log.debug("Evaluating EL: " + expression.getExpression());
    68              }
    69              Object value = expression.evaluate(jexlContext);
    70
    71              if (log.isDebugEnabled()) {
    72                  log.debug("value of expression: " + value);
    73              }
    74
    75              return value;
    76          }
    77          catch (Exception e) {
    78              log.warn("Caught exception evaluating: " + expression + ". Reason: " + e, e);
    79              return null;
    80          }
    81      }
    82  }
    83
    84  class JellyJexlContext implements JexlContext {
    85
    86      private Map vars;
    87
    88      JellyJexlContext(JellyContext context) {
    89          this.vars = new JellyMap( context );
    90      }
    91
    92      public void setVars(Map vars) {
    93          this.vars.clear();
    94          this.vars.putAll( vars );
    95      }
    96
    97      public Map getVars() {
    98          return this.vars;
    99      }
    100 }
    101
    102
    103 class JellyMap implements Map {
    104
    105     private JellyContext context;
    106
    107     JellyMap(JellyContext context) {
    108         this.context = context;
    109     }
    110
    111     public Object get(Object key) {
    112         return context.getVariable( (String) key );
    113     }
    114
    115     public void clear() {
    116         // not implemented
    117     }
    118
    119     public boolean containsKey(Object key) {
    120         return ( get( key ) != null );
    121     }
    122
    123     public boolean containsValue(Object value) {
    124         return false;
    125     }
    126
    127     public Set entrySet() {
    128         return null;
    129     }
    130
    131     public boolean isEmpty() {
    132         return false;
    133     }
    134
    135     public Set keySet() {
    136         return null;
    137     }
    138
    139     public Object put(Object key, Object value) {
    140         return null;
    141     }
    142
    143     public void putAll(Map t) {
    144         // not implemented
    145     }
    146
    147     public Object remove(Object key) {
    148         return null;
    149     }
    150
    151     public int size() {
    152         return -1;
    153     }
    154
    155     public Collection values() {
    156         return null;
    157     }
    158 }