tapestry/tapestry-framework/src/java/org/apache/tapestry/BaseComponent.java

// Copyright 2004, 2005 The Apache Software Foundation
//
// 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 org.apache.tapestry;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.tapestry.engine.IPageLoader;
import org.apache.tapestry.spec.IComponentSpecification;

/**
 * Base implementation for most components that use an HTML template.
 * 
 * @author Howard Lewis Ship
 */

public abstract class BaseComponent extends AbstractComponent implements ITemplateComponent
{
    private static final Log LOG = LogFactory.getLog(BaseComponent.class);

    private static final int OUTER_INIT_SIZE = 5;

    private IRender[] _outer;

    private int _outerCount = 0;

    /**
     * Adds an element as an outer element for the receiver. Outer elements are elements that should
     * be directly rendered by the receiver's <code>render()</code> method. That is, they are
     * top-level elements on the HTML template.
     */

    public void addOuter(IRender element)
    {
        if (_outer == null)
        {
            _outer = new IRender[OUTER_INIT_SIZE];
            _outer[0] = element;

            _outerCount = 1;
            return;
        }

        // No more room? Make the array bigger.

        if (_outerCount == _outer.length)
        {
            IRender[] newOuter;

            newOuter = new IRender[_outer.length * 2];

            System.arraycopy(_outer, 0, newOuter, 0, _outerCount);

            _outer = newOuter;
        }

        _outer[_outerCount++] = element;
    }

    public IRender[] getContainedRenderers()
    {
        return _outer;
    }
    
    public IRender[] getInnerRenderers()
    {
        return _body;
    }

    /**
     * Reads the receiver's template and figures out which elements wrap which other elements.
     *
     * @param cycle
     *          The current request.
     * @param loader
     *          The service responsible for loading / resolving a page spec.
     */

    private void readTemplate(IRequestCycle cycle, IPageLoader loader)
    {
        loader.loadTemplateForComponent(cycle, this);
    }

    /**
     * Renders the top level components contained by the receiver.
     * 
     * @since 2.0.3
     */

    protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
    {
        if (LOG.isDebugEnabled())
            LOG.debug("Begin render " + getExtendedId());
        
        for (int i = 0; i < _outerCount; i++)
            cycle.getResponseBuilder().render(writer, _outer[i], cycle);
        
        if (LOG.isDebugEnabled())
            LOG.debug("End render " + getExtendedId());
    }

    /**
     * Loads the template for the component, then invokes
     * {@link AbstractComponent#finishLoad(IRequestCycle, IPageLoader, IComponentSpecification)}.
     * Subclasses must invoke this method first, before adding any additional behavior, though its
     * usually simpler to override {@link #finishLoad()}instead.
     */

    public void finishLoad(IRequestCycle cycle, IPageLoader loader, IComponentSpecification specification)
    {
        readTemplate(cycle, loader);

        super.finishLoad(cycle, loader, specification);
    }
}