com.vaadin.ui.ClientWidget Maven / Gradle / Ivy
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/*
* Copyright 2011 Vaadin Ltd.
*
* 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 com.vaadin.ui;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import com.vaadin.terminal.gwt.client.Paintable;
import com.vaadin.terminal.gwt.widgetsetutils.CustomWidgetMapGenerator;
import com.vaadin.terminal.gwt.widgetsetutils.EagerWidgetMapGenerator;
import com.vaadin.terminal.gwt.widgetsetutils.LazyWidgetMapGenerator;
import com.vaadin.terminal.gwt.widgetsetutils.WidgetMapGenerator;
/**
* Annotation defining the default client side counterpart in GWT terminal for
* {@link Component}.
*
* With this annotation server side Vaadin component is marked to have a client
* side counterpart. The value of the annotation is the class of client side
* implementation.
*
* Note, even though client side implementation is needed during development,
* one may safely remove them from the classpath of the production server.
*
* @since 6.2
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface ClientWidget {
/**
* @return the client side counterpart for the annotated component
*/
Class value();
/**
* Depending on the used WidgetMap generator, these optional hints may be
* used to define how the client side components are loaded by the browser.
* The default is to eagerly load all widgets
* {@link EagerWidgetMapGenerator}, but if the {@link WidgetMapGenerator} is
* used by the widgetset, these load style hints are respected.
*
* Lazy loading of a widget implementation means the client side component
* is not included in the initial JavaScript application loaded when the
* application starts. Instead the implementation is loaded to the client
* when it is first needed. Lazy loaded widget can be achieved by giving
* {@link LoadStyle#LAZY} value in ClientWidget annotation.
*
* Lazy loaded widgets don't stress the size and startup time of the client
* side as much as eagerly loaded widgets. On the other hand there is a
* slight latency when lazy loaded widgets are first used as the client side
* needs to visit the server to fetch the client side implementation.
*
* The {@link LoadStyle#DEFERRED} will also not stress the initially loaded
* JavaScript file. If this load style is defined, the widget implementation
* is preemptively loaded to the browser after the application is started
* and the communication to server idles. This load style kind of combines
* the best of both worlds.
*
* Fine tunings to widget loading can also be made by overriding
* {@link WidgetMapGenerator} in the GWT module. Tunings might be helpful if
* the end users have slow connections and especially if they have high
* latency in their network. The {@link CustomWidgetMapGenerator} is an
* abstract generator implementation for easy customization. Vaadin package
* also includes {@link LazyWidgetMapGenerator} that makes as many widgets
* lazily loaded as possible.
*
* @since 6.4
*
* @return the hint for the widget set generator how the client side
* implementation should be loaded to the browser
*/
LoadStyle loadStyle() default LoadStyle.DEFERRED;
public enum LoadStyle {
/**
* The widget is included in the initial JS sent to the client.
*/
EAGER,
/**
* Not included in the initial set of widgets, but added to queue from
* which it will be loaded when network is not busy or the
* implementation is required.
*/
DEFERRED,
/**
* Loaded to the client only if needed.
*/
LAZY
}
}