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
015package org.apache.tapestry.valid;
016
017import org.apache.tapestry.AbstractComponent;
018import org.apache.tapestry.BindingException;
019import org.apache.tapestry.IForm;
020import org.apache.tapestry.IMarkupWriter;
021import org.apache.tapestry.IRequestCycle;
022import org.apache.tapestry.Tapestry;
023import org.apache.tapestry.TapestryUtils;
024import 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
035public abstract class FieldLabel extends AbstractComponent
036{
037    // Parameter
038    public abstract boolean isPrerender();
039
040    /**
041     * Gets the {@link IForm}&nbsp;and {@link IValidationDelegate delegate}, then renders the
042     * label obtained from the field. Does nothing when rewinding.
043     */
044
045    protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
046    {
047        IForm form = TapestryUtils.getForm(cycle, this);
048        
049        IFormComponent field = getField();
050        
051        if (field != null && isPrerender())
052            form.prerenderField(writer, field, getLocation());
053
054        if (cycle.isRewinding())
055            return;
056
057        String displayName = getDisplayName();
058
059        if (displayName == null)
060        {
061            if (field == null)
062                throw Tapestry.createRequiredParameterException(this, "field");
063
064            displayName = field.getDisplayName();
065
066            if (displayName == null)
067                throw new BindingException(ValidMessages.noDisplayName(this, field), this, null,
068                        getBinding("field"), null);
069        }
070
071        IValidationDelegate delegate = form.getDelegate();
072
073        String id = field == null ? null : field.getClientId();
074
075        delegate.writeLabelPrefix(field, writer, cycle);
076
077        writer.begin("label");
078
079        if (id != null)
080            writer.attribute("for", id);
081        
082        delegate.writeLabelAttributes(writer, cycle, field);
083        renderInformalParameters(writer, cycle);
084
085        writer.print(displayName, getRaw());
086
087        writer.end();
088
089        delegate.writeLabelSuffix(field, writer, cycle);
090    }
091
092    /** displayName parameter */
093    public abstract String getDisplayName();
094
095    /** field parameter */
096    public abstract IFormComponent getField();
097
098    /** raw parameter */
099    public abstract boolean getRaw();
100}