001    // Copyright 2004, 2005 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.tapestry;
016    
017    import org.apache.commons.logging.Log;
018    import org.apache.commons.logging.LogFactory;
019    import org.apache.tapestry.engine.IPageLoader;
020    import org.apache.tapestry.spec.IComponentSpecification;
021    
022    /**
023     * Base implementation for most components that use an HTML template.
024     * 
025     * @author Howard Lewis Ship
026     */
027    
028    public class BaseComponent extends AbstractComponent implements ITemplateComponent
029    {
030        private static final Log LOG = LogFactory.getLog(BaseComponent.class);
031    
032        private static final int OUTER_INIT_SIZE = 5;
033    
034        private IRender[] _outer;
035    
036        private int _outerCount = 0;
037    
038        /**
039         * Adds an element as an outer element for the receiver. Outer elements are elements that should
040         * be directly rendered by the receiver's <code>render()</code> method. That is, they are
041         * top-level elements on the HTML template.
042         */
043    
044        public void addOuter(IRender element)
045        {
046            if (_outer == null)
047            {
048                _outer = new IRender[OUTER_INIT_SIZE];
049                _outer[0] = element;
050    
051                _outerCount = 1;
052                return;
053            }
054    
055            // No more room? Make the array bigger.
056    
057            if (_outerCount == _outer.length)
058            {
059                IRender[] newOuter;
060    
061                newOuter = new IRender[_outer.length * 2];
062    
063                System.arraycopy(_outer, 0, newOuter, 0, _outerCount);
064    
065                _outer = newOuter;
066            }
067    
068            _outer[_outerCount++] = element;
069        }
070    
071        /**
072         * Reads the receiver's template and figures out which elements wrap which other elements.
073         */
074    
075        private void readTemplate(IRequestCycle cycle, IPageLoader loader)
076        {
077            loader.loadTemplateForComponent(cycle, this);
078        }
079    
080        /**
081         * Renders the top level components contained by the receiver.
082         * 
083         * @since 2.0.3
084         */
085    
086        protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
087        {
088            if (LOG.isDebugEnabled())
089                LOG.debug("Begin render " + getExtendedId());
090    
091            for (int i = 0; i < _outerCount; i++)
092                _outer[i].render(writer, cycle);
093    
094            if (LOG.isDebugEnabled())
095                LOG.debug("End render " + getExtendedId());
096        }
097    
098        /**
099         * Loads the template for the component, then invokes
100         * {@link AbstractComponent#finishLoad(IRequestCycle, IPageLoader, IComponentSpecification)}.
101         * Subclasses must invoke this method first, before adding any additional behavior, though its
102         * usually simpler to override {@link #finishLoad()}instead.
103         */
104    
105        public void finishLoad(IRequestCycle cycle, IPageLoader loader, IComponentSpecification specification)
106        {
107            readTemplate(cycle, loader);
108    
109            super.finishLoad(cycle, loader, specification);
110        }
111    }