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.*;
018    import org.apache.tapestry.form.IFormComponent;
019    
020    /**
021     * Used to label an {@link IFormComponent}. Because such fields know their
022     * displayName (user-presentable name), there's no reason to hard code the label
023     * in a page's HTML template (this also helps with localization). [ <a
024     * href="../../../../../ComponentReference/FieldLabel.html">Component Reference
025     * </a>]
026     * 
027     * @author Howard Lewis Lewis Ship
028     */
029    
030    public abstract class FieldLabel extends AbstractComponent
031    {
032    
033        // Parameter
034        public abstract boolean isPrerender();
035    
036        /**
037         * Gets the {@link IForm}&nbsp;and {@link IValidationDelegate delegate},
038         * then renders the label obtained from the field. Does nothing when
039         * 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 && isPrerender())
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, getBinding("field"), null);
065            }
066            
067            IValidationDelegate delegate = form.getDelegate();
068            
069            String id = (field == null) ? null : field.getClientId();
070            
071            if (field != null)
072                delegate.writeLabelPrefix(field, writer, cycle);
073            
074            writer.begin("label");
075    
076            renderInformalParameters(writer, cycle);
077    
078            if (id != null) 
079                writer.attribute("for", id);
080                    
081            delegate.writeLabelAttributes(writer, cycle, field);
082            
083            delegate.beforeLabelText(writer, cycle, field);
084            
085            writer.print(displayName, getRaw());
086            
087            delegate.afterLabelText(writer, cycle, field);
088            
089            writer.end();
090            
091            if (field != null)
092                delegate.writeLabelSuffix(field, writer, cycle);
093        }
094    
095        /** displayName parameter. */
096        public abstract String getDisplayName();
097    
098        /** field parameter. */
099        public abstract IFormComponent getField();
100    
101        /** raw parameter. */
102        public abstract boolean getRaw();
103    }