    001    // Copyright 2009 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.corelib.base;
    016
    017    import org.apache.tapestry5.BindingConstants;
    018    import org.apache.tapestry5.Block;
    019    import org.apache.tapestry5.ComponentResources;
    020    import org.apache.tapestry5.MarkupWriter;
    021    import org.apache.tapestry5.annotations.Parameter;
    022    import org.apache.tapestry5.annotations.SupportsInformalParameters;
    023    import org.apache.tapestry5.ioc.annotations.Inject;
    024
    025    /**
    026     * Base class for {@link org.apache.tapestry5.corelib.components.If} and {@link org.apache.tapestry5.corelib.components.Unless}.
    027     * Will render its body or the block from its else parameter.  If it renders anything and it has an element name, then
    028     * it renders the element and its informal parameters.
    029     */
    030    @SupportsInformalParameters
    031    public abstract class AbstractConditional
    032    {
    033        @Inject
    034        private ComponentResources resources;
    035
    036        /**
    037         * Performs the test via the parameters; return true to render the body of the component, false to render the else
    038         * block (or nothing).
    039         *
    040         * @return true to render body
    041         */
    042        protected abstract boolean test();
    043
    044        /**
    045         * An alternate {@link org.apache.tapestry5.Block} to render if {@link #test()} is false. The default, null, means
    046         * render nothing in that situation.
    047         */
    048        @Parameter(name = "else", defaultPrefix = BindingConstants.LITERAL)
    049        private Block elseBlock;
    050
    051        private boolean renderTag;
    052
    053        /**
    054         * Returns null if the {@link #test()} is true, which allows normal rendering (of the body). If the test parameter
    055         * is false, returns the else parameter (this may also be null).
    056         */
    057        Object beginRender(MarkupWriter writer)
    058        {
    059            Block toRender = test() ? resources.getBody() : elseBlock;
    060
    061            String elementName = resources.getElementName();
    062
    063            renderTag = toRender != null && elementName != null;
    064
    065            if (renderTag)
    066            {
    067                writer.element(elementName);
    068                resources.renderInformalParameters(writer);
    069            }
    070
    071            return toRender;
    072        }
    073
    074        /**
    075         * If {@link #test()} is true, then the body is rendered, otherwise not. The component does not have a template or
    076         * do any other rendering besides its body.
    077         */
    078        boolean beforeRenderBody()
    079        {
    080            return false;
    081        }
    082
    083        void afterRenderBody(MarkupWriter writer)
    084        {
    085            if (renderTag)
    086                writer.end();
    087        }
    088
    089
    090    }