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.tapestry.IMarkupWriter;
018    import org.apache.tapestry.IRequestCycle;
019    import org.apache.tapestry.valid.ValidatorException;
020    
021    /**
022     * Implements a component that manages an HTML &lt;input type=checkbox&gt; form element. [ <a
023     * href="../../../../../ComponentReference/Checkbox.html">Component Reference </a>]
024     * <p>
025     * As of 4.0, this component can be validated.
026     * 
027     * @author Howard Lewis Ship
028     * @author Paul Ferraro
029     */
030    public abstract class Checkbox extends AbstractFormComponent implements ValidatableField
031    {
032        /**
033         * @see org.apache.tapestry.form.validator.AbstractRequirableField#renderRequirableFormComponent(org.apache.tapestry.IMarkupWriter,
034         *      org.apache.tapestry.IRequestCycle)
035         */
036        protected void renderFormComponent(IMarkupWriter writer, IRequestCycle cycle)
037        {
038            writer.beginEmpty("input");
039            writer.attribute("type", "checkbox");
040    
041            writer.attribute("name", getName());
042    
043            if (isDisabled())
044                writer.attribute("disabled", "disabled");
045    
046            if (getValue())
047                writer.attribute("checked", "checked");
048    
049            renderIdAttribute(writer, cycle);
050    
051            renderInformalParameters(writer, cycle);
052    
053            writer.closeTag();
054        }
055    
056        /**
057         * In traditional HTML, many checkboxes would have the same name but different values. Under
058         * Tapestry, it makes more sense to have different names and a fixed value. For a checkbox, we
059         * only care about whether the name appears as a request parameter.
060         */
061        protected void rewindFormComponent(IMarkupWriter writer, IRequestCycle cycle)
062        {
063            String value = cycle.getParameter(getName());
064            
065            try
066            {
067                // This is atypical validation - since this component does not explicitly bind to an object
068                getValidatableFieldSupport().validate(this, writer, cycle, value);
069    
070                setValue(value != null);
071            }
072            catch (ValidatorException e)
073            {
074                getForm().getDelegate().record(e);
075            }
076        }
077    
078        public abstract boolean getValue();
079    
080        public abstract void setValue(boolean selected);
081    
082        /**
083         * Injected.
084         */
085        public abstract ValidatableFieldSupport getValidatableFieldSupport();
086    
087        /**
088         * @see org.apache.tapestry.form.AbstractFormComponent#isRequired()
089         */
090        public boolean isRequired()
091        {
092            return getValidatableFieldSupport().isRequired(this);
093        }
094    }