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()) return;
058    
059            String displayName = getDisplayName();
060    
061            if (displayName == null)
062            {
063                if (field == null)
064                    throw Tapestry.createRequiredParameterException(this, "field");
065    
066                displayName = field.getDisplayName();
067    
068                if (displayName == null)
069                    throw new BindingException(ValidMessages.noDisplayName(this,
070                            field), this, null, getBinding("field"), null);
071            }
072    
073            IValidationDelegate delegate = form.getDelegate();
074    
075            String id = field == null ? null : field.getClientId();
076    
077            delegate.writeLabelPrefix(field, writer, cycle);
078    
079            writer.begin("label");
080    
081            if (id != null) writer.attribute("for", id);
082    
083            delegate.writeLabelAttributes(writer, cycle, field);
084            renderInformalParameters(writer, cycle);
085    
086            writer.print(displayName, getRaw());
087    
088            writer.end();
089    
090            delegate.writeLabelSuffix(field, writer, cycle);
091        }
092    
093        /** displayName parameter. */
094        public abstract String getDisplayName();
095    
096        /** field parameter. */
097        public abstract IFormComponent getField();
098    
099        /** raw parameter. */
100        public abstract boolean getRaw();
101    }