001    // Copyright 2007, 2010 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.tapestry5;
016    
017    import org.apache.tapestry5.services.javascript.JavaScriptSupport;
018    
019    /**
020     * Interface for any kind of object (typically, a component) that can provide a {@linkplain #getClientId() client-side
021     * id}, typically used in the generation of client-side (JavaScript) logic. For components, the client id will be null
022     * or inaccurate until after the component has rendered itself. Inside of any kind of loop, the clientId property is
023     * only accurate just after the component has rendered, and before it renders again.
024     * <p/>
025     * Some components must be configured to provide a client id. In many cases, the client id matches the component's
026     * {@linkplain ComponentResourcesCommon#getId() component id}, typically passed through
027     * {@link JavaScriptSupport#allocateClientId(String)} to ensure uniqueness.
028     */
029    public interface ClientElement
030    {
031        /**
032         * Returns a unique id for the element. This value will be unique for any given rendering of a page. This value is
033         * intended for use as the id attribute of the client-side element, and will be used with any DHTML/Ajax related
034         * JavaScript.
035         */
036        String getClientId();
037    }