001// Copyright 2009-2013 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
015package org.apache.tapestry5.corelib.base;
016
017import org.apache.tapestry5.BindingConstants;
018import org.apache.tapestry5.Block;
019import org.apache.tapestry5.ComponentResources;
020import org.apache.tapestry5.MarkupWriter;
021import org.apache.tapestry5.annotations.Parameter;
022import org.apache.tapestry5.annotations.SupportsInformalParameters;
023import 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 * @tapestrydoc
031 */
032@SupportsInformalParameters
033public abstract class AbstractConditional
034{
035    @Inject
036    private ComponentResources resources;
037
038    /**
039     * Performs the test via the parameters; return true to render the body of the component, false to render the else
040     * block (or nothing).
041     *
042     * @return true to render body
043     */
044    protected abstract boolean test();
045
046    /**
047     * An alternate {@link org.apache.tapestry5.Block} to render if {@link #test()} is false. The default, null, means
048     * render nothing in that situation.
049     */
050    @Parameter(name = "else", defaultPrefix = BindingConstants.LITERAL)
051    private Block elseBlock;
052
053    private boolean renderTag;
054
055    /**
056     * Returns null if the {@link #test()} is true, which allows normal rendering (of the body). If the test parameter
057     * is false, returns the else parameter (this may also be null).
058     */
059    Object beginRender(MarkupWriter writer)
060    {
061        boolean enabled = test();
062
063        Block toRender = enabled ? resources.getBody() : elseBlock;
064
065        String elementName = resources.getElementName();
066
067        renderTag = enabled && elementName != null;
068
069        if (renderTag)
070        {
071            writer.element(elementName);
072            resources.renderInformalParameters(writer);
073        }
074
075        return toRender;
076    }
077
078    /**
079     * If {@link #test()} is true, then the body is rendered, otherwise not. The component does not have a template or
080     * do any other rendering besides its body (and possibly an element around its body).
081     */
082    boolean beforeRenderBody()
083    {
084        return false;
085    }
086
087    void afterRender(MarkupWriter writer)
088    {
089        if (renderTag)
090        {
091            writer.end();
092        }
093    }
094
095
096}