VelocityPanel.java

package com.rectang.xsm.wicket;

import com.rectang.xsm.Engine;
import com.rectang.xsm.Theme;
import com.rectang.xsm.io.XSMDocument;
import com.rectang.xsm.pages.XSMSession;
import com.rectang.xsm.site.DocumentPage;
import org.apache.velocity.VelocityContext;
import org.apache.wicket.MarkupContainer;
import org.apache.wicket.markup.IMarkupCacheKeyProvider;
import org.apache.wicket.markup.IMarkupResourceStreamProvider;
import org.apache.wicket.markup.html.panel.Panel;
import org.apache.wicket.model.IModel;
import org.apache.wicket.model.Model;
import org.apache.wicket.model.StringResourceModel;
import org.apache.wicket.util.resource.IResourceStream;
import org.apache.wicket.util.resource.StringResourceStream;

import java.io.StringWriter;
import java.util.Map;

/**
 * A simple velocity panel that renders content from a velocity template instead of html markup.
 * <p/>
 * Copyright Kotikan Ltd 2011
 * Created: 13/11/2011
 *
 * @author Andrew Williams
 * @since 1.0
 */
public class VelocityPanel
        extends Panel
        implements IMarkupResourceStreamProvider, IMarkupCacheKeyProvider
{
    public VelocityPanel( String id )
    {
        super( id );
    }

    public VelocityPanel( String id, IModel model )
    {
        super( id, model );
    }

    public VelocityPanel( String id, final String template )
    {
        super( id, new Model()
        {
            @Override
            public String getObject()
            {
                return template;
            }
        } );
    }

    // TODO improve this "never cache" code with something that stores it until change needed...
    public String getCacheKey( MarkupContainer markupContainer, Class aClass )
    {
        return null;
    }

    public IResourceStream getMarkupResourceStream( MarkupContainer markupContainer, Class aClass )
    {
        return new StringResourceStream( "<wicket:panel>" + evaluateVelocityTemplate() + "</wicket:panel>" );
    }

    /**
     * Evaluates the template from our model and returns the result.
     * @return the result of evaluating the velocity template
     */
    private String evaluateVelocityTemplate()
    {
        XSMSession session = (XSMSession) getSession();
        XSMDocument doc = null;
        com.rectang.xsm.site.Page page = null;
        if ( getPage() instanceof com.rectang.xsm.pages.cms.Page )
        {
            page = ((com.rectang.xsm.pages.cms.Page) getPage()).getXSMPage();
            if ( page instanceof DocumentPage )
            {
                doc = XSMDocument.getXSMDoc( session.getSite(), (DocumentPage) page );
            }
        }
        final Map<String, Object> map = Engine.getContext( doc, page, null, null, session.getSite(), "",
                session.getUser() );
        final VelocityContext context = new VelocityContext( map );

        StringWriter out = new StringWriter();
        try
        {
            // execute the velocity script and capture the output in writer
            Engine.getVelocityEngine().evaluate( context, out, getClass().getSimpleName(), getDefaultModelObjectAsString() );

            // replace the tag's body the Velocity output
            return out.toString();
        }
        catch ( Exception e )
        {
            e.printStackTrace();
            // TODO handle displaying this error for debug
            return null;
        }
    }
}