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.form;
016    
017    import org.apache.hivemind.ApplicationRuntimeException;
018    import org.apache.tapestry.IForm;
019    import org.apache.tapestry.IMarkupWriter;
020    import org.apache.tapestry.IRequestCycle;
021    import org.apache.tapestry.Tapestry;
022    
023    /**
024     *  Implements a component that manages an HTML <input type=radio> form element.
025     *  Such a component must be wrapped (possibly indirectly)
026     *  inside a {@link RadioGroup} component.
027     *
028     *  [<a href="../../../../../ComponentReference/Radio.html">Component Reference</a>]
029     *
030     *
031     *  <p>{@link Radio} and {@link RadioGroup} are generally not used (except
032     *  for very special cases).  Instead, a {@link PropertySelection} component is used.
033     *
034     *
035     *  @author Howard Lewis Ship
036     *
037     **/
038    
039    public abstract class Radio extends AbstractFormComponent
040    {
041        /**
042         *  Renders the form element, or responds when the form containing the element
043         *  is submitted (by checking {@link Form#isRewinding()}.
044         *
045         *
046         **/
047    
048        protected void renderFormComponent(IMarkupWriter writer, IRequestCycle cycle)
049        {
050            RadioGroup group = RadioGroup.get(cycle);
051    
052            if (group == null)
053                throw new ApplicationRuntimeException(Tapestry.getMessage("Radio.must-be-contained-by-group"),
054                                                      this,
055                                                      null,
056                                                      null);
057    
058            int option = group.getNextOptionId();
059    
060            setClientId(group.getName()+option);
061            setName(group.getName());
062    
063            writer.beginEmpty("input");
064    
065            writer.attribute("type", "radio");
066    
067            writer.attribute("name", getName());
068    
069            renderIdAttribute(writer, cycle);
070    
071            // As the group if the value for this Radio matches the selection
072            // for the group as a whole; if so this is the default radio and is checked.
073    
074            if (group.isSelection(getValue()))
075                writer.attribute("checked", "checked");
076    
077            if (isDisabled() || group.isDisabled())
078                writer.attribute("disabled", "disabled");
079    
080            // The value for the Radio matches the option number (provided by the RadioGroup).
081            // When the form is submitted, the RadioGroup will know which option was,
082            // in fact, selected by the user.
083    
084            writer.attribute("value", option);
085    
086            renderInformalParameters(writer, cycle);
087    
088            writer.closeTag();
089        }
090    
091        protected void rewindFormComponent(IMarkupWriter writer, IRequestCycle cycle)
092        {
093            RadioGroup group = RadioGroup.get(cycle);
094    
095            if (group == null)
096                throw new ApplicationRuntimeException(
097                        Tapestry.getMessage("Radio.must-be-contained-by-group"),
098                        this,
099                        null,
100                        null);
101    
102            int option = group.getNextOptionId();
103    
104            setClientId(group.getName()+option);
105            setName(group.getName());
106    
107            // If not disabled and this is the selected button within the radio group,
108            // then update set the selection from the group to the value for this
109            // radio button.  This will update the selected parameter of the RadioGroup.
110    
111            if (!isDisabled() && !group.isDisabled() && group.isSelected(option))
112                group.updateSelection(getValue());
113        }
114    
115        /**
116         * Overridden to do nothing so that special {@link RadioGroup} semantics are handled properly.
117         * @param form The form to set the name on.
118         */
119        protected void setName(IForm form)
120        {
121        }
122    
123        public abstract boolean isDisabled();
124    
125        public abstract Object getValue();
126    }