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
028     * displayName (user-presentable name), there's no reason to hard code the label
029     * in a page's HTML template (this also helps with localization). [ <a
030     * href="../../../../../ComponentReference/FieldLabel.html">Component Reference
031     * </a>]
032     * 
033     * @author Howard Lewis Lewis Ship
034     */
035    
036    public abstract class FieldLabel extends AbstractComponent
037    {
038    
039        // Parameter
040        public abstract boolean isPrerender();
041    
042        /**
043         * Gets the {@link IForm}&nbsp;and {@link IValidationDelegate delegate},
044         * then renders the label obtained from the field. Does nothing when
045         * rewinding.
046         */
047    
048        protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
049        {
050            IForm form = TapestryUtils.getForm(cycle, this);
051    
052            IFormComponent field = getField();
053    
054            if (field != null && isPrerender())
055                form.prerenderField(writer, field, getLocation());
056    
057            if (cycle.isRewinding()) 
058                return;
059    
060            String displayName = getDisplayName();
061    
062            if (displayName == null)
063            {
064                if (field == null)
065                    throw Tapestry.createRequiredParameterException(this, "field");
066                
067                displayName = field.getDisplayName();
068                
069                if (displayName == null)
070                    throw new BindingException(ValidMessages.noDisplayName(this,
071                            field), this, null, getBinding("field"), null);
072            }
073    
074            IValidationDelegate delegate = form.getDelegate();
075    
076            String id = field == null ? null : field.getClientId();
077            
078            delegate.writeLabelPrefix(field, writer, cycle);
079            
080            writer.begin("label");
081    
082            if (id != null) writer.attribute("for", id);
083            
084            delegate.writeLabelAttributes(writer, cycle, field);
085            renderInformalParameters(writer, cycle);
086            
087            writer.print(displayName, getRaw());
088    
089            writer.end();
090    
091            delegate.writeLabelSuffix(field, writer, cycle);
092        }
093    
094        /** displayName parameter. */
095        public abstract String getDisplayName();
096    
097        /** field parameter. */
098        public abstract IFormComponent getField();
099    
100        /** raw parameter. */
101        public abstract boolean getRaw();
102    }