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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.tags.core;
    17
    18  import org.apache.commons.jelly.JellyTagException;
    19  import org.apache.commons.jelly.TagSupport;
    20  import org.apache.commons.jelly.XMLOutput;
    21  import org.apache.commons.jelly.expression.Expression;
    22
    23  /*** A tag which conditionally evaluates its body based on some condition
    24    *
    25    * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
    26    * @version $Revision: 155420 $
    27    */
    28  public class WhenTag extends TagSupport {
    29
    30      /*** The expression to evaluate. */
    31      private Expression test;
    32
    33      public WhenTag() {
    34      }
    35
    36      // Tag interface
    37      //-------------------------------------------------------------------------
    38      public void doTag(XMLOutput output) throws JellyTagException {
    39          ChooseTag tag = (ChooseTag) findAncestorWithClass( ChooseTag.class );
    40          if ( tag == null ) {
    41              throw new JellyTagException( "This tag must be enclosed inside a <choose> tag" );
    42          }
    43          if ( ! tag.isBlockEvaluated() && test != null ) {
    44              if ( test.evaluateAsBoolean( context ) ) {
    45                  tag.setBlockEvaluated(true);
    46                  invokeBody(output);
    47              }
    48          }
    49      }
    50
    51      // Properties
    52      //-------------------------------------------------------------------------
    53
    54      /*** Sets the expression to evaluate. */
    55      public void setTest(Expression test) {
    56          this.test = test;
    57      }
    58
    59  }