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.valid;
016    
017    import org.apache.tapestry.AbstractComponent;
018    import org.apache.tapestry.BindingException;
019    import org.apache.tapestry.IForm;
020    import org.apache.tapestry.IMarkupWriter;
021    import org.apache.tapestry.IRequestCycle;
022    import org.apache.tapestry.Tapestry;
023    import org.apache.tapestry.TapestryUtils;
024    import org.apache.tapestry.form.IFormComponent;
025    
026    /**
027     * Used to label an {@link IFormComponent}. Because such fields know their displayName
028     * (user-presentable name), there's no reason to hard code the label in a page's HTML template (this
029     * also helps with localization). [ <a
030     * href="../../../../../ComponentReference/FieldLabel.html">Component Reference </a>]
031     * 
032     * @author Howard Lewis Lewis Ship
033     */
034    
035    public abstract class FieldLabel extends AbstractComponent
036    {
037        /**
038         * Gets the {@link IForm}&nbsp;and {@link IValidationDelegate delegate}, then renders the
039         * label obtained from the field. Does nothing when rewinding.
040         */
041    
042        protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
043        {
044            IForm form = TapestryUtils.getForm(cycle, this);
045    
046            IFormComponent field = getField();
047    
048            if (field != null)
049                form.prerenderField(writer, field, getLocation());
050    
051            if (cycle.isRewinding())
052                return;
053    
054            String displayName = getDisplayName();
055    
056            if (displayName == null)
057            {
058                if (field == null)
059                    throw Tapestry.createRequiredParameterException(this, "field");
060    
061                displayName = field.getDisplayName();
062    
063                if (displayName == null)
064                    throw new BindingException(ValidMessages.noDisplayName(this, field), this, null,
065                            getBinding("field"), null);
066            }
067    
068            IValidationDelegate delegate = form.getDelegate();
069    
070            String id = field == null ? null : field.getClientId();
071    
072            delegate.writeLabelPrefix(field, writer, cycle);
073    
074            writer.begin("label");
075    
076            if (id != null)
077                writer.attribute("for", id);
078    
079            // TODO: Introduce a IValidationDelegate decoration method for inside the
080            // <label> tag.
081    
082            renderInformalParameters(writer, cycle);
083    
084            writer.print(displayName, getRaw());
085    
086            writer.end();
087    
088            delegate.writeLabelSuffix(field, writer, cycle);
089        }
090    
091        /** displayName parameter */
092        public abstract String getDisplayName();
093    
094        /** field parameter */
095        public abstract IFormComponent getField();
096    
097        /** raw parameter */
098        public abstract boolean getRaw();
099    }