// Copyright 2006, 2007 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package org.apache.tapestry.corelib.components;
import org.apache.tapestry.ComponentResources;
import org.apache.tapestry.Field;
import org.apache.tapestry.MarkupWriter;
import org.apache.tapestry.ValidationDecorator;
import org.apache.tapestry.annotations.AfterRender;
import org.apache.tapestry.annotations.BeforeRenderBody;
import org.apache.tapestry.annotations.BeginRender;
import org.apache.tapestry.annotations.Environmental;
import org.apache.tapestry.annotations.Inject;
import org.apache.tapestry.annotations.Parameter;
import org.apache.tapestry.annotations.SupportsInformalParameters;
import org.apache.tapestry.dom.Element;
import org.apache.tapestry.services.Heartbeat;
/** Generates a <label> element for a particular field. */
@SupportsInformalParameters
public class Label
{
/**
* The for parameter is used to identify the {@link Field} linked to this label (it is named
* this way because it results in the for attribute of the label element).
*/
@Parameter(name = "for", required = true, defaultPrefix = "component")
private Field _field;
@Environmental
private Heartbeat _heartbeat;
@Environmental
private ValidationDecorator _decorator;
@Inject
private ComponentResources _resources;
@BeginRender
void begin(MarkupWriter writer)
{
final Field field = _field;
final Element element = writer.element("label");
_resources.renderInformalParameters(writer);
// Uh oh! Referencing a private field (that happens to get instrumented up the wazoo) from
// a inner class causes a java.lang.Verify error (Unable to pop operand off an empty stack).
// Perhaps this is a Javassist error? Shouldn't the inner class be going through a synthetic
// accessor method of some kind? Resolved by assigning to a local variable and referencing
// that. Layers on layers, oh my!
final ValidationDecorator decorator = _decorator;
// Since we don't know if the field has rendered yet, we need to defer writing the for
// attribute until we know the field has rendered (and set its clientId property). That's
// exactly what Heartbeat is for.
Runnable command = new Runnable()
{
public void run()
{
String fieldId = field.getClientId();
element.forceAttributes("for", fieldId, "id", fieldId + ":label");
decorator.insideLabel(field, element);
}
};
_heartbeat.defer(command);
}
@BeforeRenderBody
boolean renderBody()
{
// Don't render the body of the component even if there is one.
return false;
}
@AfterRender
void after(MarkupWriter writer)
{
writer.write(_field.getLabel());
writer.end(); // label
}
}