    001// Licensed under the Apache License, Version 2.0 (the "License");
    002// you may not use this file except in compliance with the License.
    003// You may obtain a copy of the License at
    004//
    005// http://www.apache.org/licenses/LICENSE-2.0
    006//
    007// Unless required by applicable law or agreed to in writing, software
    008// distributed under the License is distributed on an "AS IS" BASIS,
    009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    010// See the License for the specific language governing permissions and
    011// limitations under the License.
    012
    013package org.apache.tapestry5.corelib.components;
    014
    015import org.apache.tapestry5.*;
    016import org.apache.tapestry5.annotations.Environmental;
    017import org.apache.tapestry5.annotations.HeartbeatDeferred;
    018import org.apache.tapestry5.annotations.Parameter;
    019import org.apache.tapestry5.annotations.SupportsInformalParameters;
    020import org.apache.tapestry5.dom.Element;
    021import org.apache.tapestry5.http.TapestryHttpSymbolConstants;
    022import org.apache.tapestry5.ioc.annotations.Inject;
    023import org.apache.tapestry5.ioc.annotations.Symbol;
    024import org.apache.tapestry5.ioc.internal.util.InternalUtils;
    025import org.apache.tapestry5.services.javascript.JavaScriptSupport;
    026
    027/**
    028 * Generates a &lt;label&gt; element for a particular field. It writes the CSS class "control-label".
    029 *
    030 * A Label will render its body, if it has one. However, in most cases it will not have a body, and will render its
    031 * {@linkplain org.apache.tapestry5.Field#getLabel() field's label} as its body. Remember, however, that it is the
    032 * field label that will be used in any error messages. The Label component allows for client- and server-side
    033 * validation error decorations.
    034 *
    035 * @tapestrydoc
    036 */
    037@SupportsInformalParameters
    038public class Label
    039{
    040    /**
    041     * The for parameter is used to identify the {@link Field} linked to this label (it is named this way because it
    042     * results in the for attribute of the label element).
    043     */
    044    @Parameter(name = "for", required = true, allowNull = false, defaultPrefix = BindingConstants.COMPONENT)
    045    private Field field;
    046
    047    /**
    048     * Used to explicitly set the client-side id of the element for this component. Normally this is not
    049     * bound (or null) and {@link org.apache.tapestry5.services.javascript.JavaScriptSupport#allocateClientId(org.apache.tapestry5.ComponentResources)}
    050     * is used to generate a unique client-id based on the component's id. In some cases, when creating client-side
    051     * behaviors, it is useful to explicitly set a unique id for an element using this parameter.
    052     *
    053     * Certain values, such as "submit", "method", "reset", etc., will cause client-side conflicts and are not allowed; using such will
    054     * cause a runtime exception.
    055     * @since 5.6.0
    056     */
    057    @Parameter(defaultPrefix = BindingConstants.LITERAL)
    058    private String clientId;
    059
    060    @Environmental
    061    private ValidationDecorator decorator;
    062
    063    @Inject
    064    private ComponentResources resources;
    065
    066    @Inject
    067    private JavaScriptSupport javaScriptSupport;
    068
    069    @Inject
    070    @Symbol(TapestryHttpSymbolConstants.PRODUCTION_MODE)
    071    private boolean productionMode;
    072
    073    /**
    074     * If true, then the body of the label element (in the template) is ignored. This is used when a designer places a
    075     * value inside the &lt;label&gt; element for WYSIWYG purposes, but it should be replaced with a different
    076     * (probably, localized) value at runtime. The default is false, so a body will be used if present and the field's
    077     * label will only be used if the body is empty or blank.
    078     */
    079    @Parameter
    080    private boolean ignoreBody;
    081
    082    private Element labelElement;
    083
    084    private String string;
    085
    086    private String string2;
    087
    088    boolean beginRender(MarkupWriter writer)
    089    {
    090        decorator.beforeLabel(field);
    091
    092        labelElement = writer.element("label", "class", "control-label");
    093
    094        resources.renderInformalParameters(writer);
    095
    096        // Since we don't know if the field has rendered yet, we need to defer writing the for and id
    097        // attributes until we know the field has rendered (and set its clientId property). That's
    098        // exactly what Heartbeat is for.
    099
    100        updateAttributes();
    101
    102        return !ignoreBody;
    103    }
    104
    105    @HeartbeatDeferred
    106    private void updateAttributes()
    107    {
    108        String fieldId = field.getClientId();
    109
    110        if (!productionMode && fieldId == null)
    111        {
    112            // TAP5-2500
    113            String warningText = "The Label component " + resources.getCompleteId()
    114              + " is linked to a Field that failed to return a clientId. The 'for' attibute will not be rendered.";
    115            javaScriptSupport.require("t5/core/console").invoke("warn").with(warningText);
    116        }
    117
    118        String id = clientId != null ? clientId : javaScriptSupport.allocateClientId(fieldId + "-label");
    119        labelElement.attribute("id", id);
    120        labelElement.forceAttributes("for", fieldId);
    121
    122        if (fieldId != null)
    123        {
    124            Element input = labelElement.getDocument().getElementById(field.getClientId());
    125            if (input != null)
    126            {
    127                input.attribute("aria-labelledby", id);
    128            }
    129        }
    130
    131        decorator.insideLabel(field, labelElement);
    132    }
    133
    134    void afterRender(MarkupWriter writer)
    135    {
    136        // If the Label element has a body that renders some non-blank output, that takes precedence
    137        // over the label string provided by the field.
    138
    139        boolean bodyIsBlank = InternalUtils.isBlank(labelElement.getChildMarkup());
    140
    141        if (bodyIsBlank)
    142            writer.write(field.getLabel());
    143
    144        writer.end(); // label
    145
    146        decorator.afterLabel(field);
    147    }
    148}