001    // Copyright 2004, 2005 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    //     http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry.contrib.components;
016    
017    import org.apache.hivemind.ApplicationRuntimeException;
018    import org.apache.tapestry.IMarkupWriter;
019    import org.apache.tapestry.IRequestCycle;
020    import org.apache.tapestry.Tapestry;
021    import org.apache.tapestry.components.Conditional;
022    
023    /**
024     *  Represents an alternative whithin a {@link Choose} component. 
025     *  The default alternative is described by the Otherwise component.
026     *
027     *  [<a href="../../../../../../ComponentReference/contrib.When.html">Component Reference</a>]
028     *
029     *  @author David Solis
030     * 
031     **/
032    public abstract class When extends Conditional
033    {
034        /** Parent of this component. */
035    
036        private Choose _choose;
037    
038        /**
039         *  Renders its wrapped components only if the condition is true and its parent {@link Choose}
040         *  allows it. In addition, if element is specified, can emulate that HTML element.
041         *
042         **/
043    
044        protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
045        {
046            Choose choose = getChoose();
047    
048            if (choose == null)
049                throw new ApplicationRuntimeException(
050                    Tapestry.getMessage("When.must-be-contained-by-choose"),
051                    this,
052                    null,
053                    null);
054    
055            if (!choose.isConditionMet() && getCondition())
056            {
057                choose.setConditionMet(true);
058                super.renderComponent(writer, cycle);
059            }
060        }
061    
062        protected boolean evaluateCondition()
063        {
064            return true;
065        }
066    
067        public boolean getInvert()
068        {
069            // This component doesn't require invert parameter.
070            return false;
071        }
072    
073        /**
074         *  @return Choose
075         */
076        public Choose getChoose()
077        {
078            return _choose;
079        }
080    
081        /**
082         *  Sets the choose.
083         *  @param value The choose to set
084         */
085        public void setChoose(Choose value)
086        {
087            _choose = value;
088        }
089    
090    }