ResourceTemplateResponseWriter.java

/**
 *
 * Copyright 2009-2011 Rickard Öberg AB
 *
 * 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.qi4j.library.rest.server.restlet.responsewriter;

import freemarker.template.Configuration;
import freemarker.template.Template;
import freemarker.template.TemplateException;
import java.io.IOException;
import java.io.Writer;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.qi4j.api.injection.scope.Service;
import org.qi4j.api.value.ValueDescriptor;
import org.restlet.Response;
import org.restlet.data.MediaType;
import org.restlet.representation.Representation;
import org.restlet.representation.WriterRepresentation;
import org.restlet.resource.ResourceException;
import org.restlet.service.MetadataService;

/**
 * JAVADOC
 */
public class ResourceTemplateResponseWriter extends AbstractResponseWriter
{
    private static final List<MediaType> supportedMediaTypes = Arrays.asList( MediaType.TEXT_HTML, MediaType.APPLICATION_ATOM );

    @Service
    private Configuration cfg;

    @Service
    private MetadataService metadataService;

    Set<String> skip = new HashSet<String>();

    @Override
    public boolean writeResponse( final Object result, final Response response )
        throws ResourceException
    {
        MediaType type = getVariant( response.getRequest(), ENGLISH, supportedMediaTypes ).getMediaType();
        if( type != null )
        {
            // Try to find template for this specific resource
            StringBuilder templateBuilder = (StringBuilder) response.getRequest().getAttributes().get( "template" );
            String templateName = templateBuilder.toString();

            if( result instanceof ValueDescriptor )
            {
                templateName += "_form";
            }

            final String extension = metadataService.getExtension( type );
            templateName += "." + extension;

            // Have we failed on this one before, then don't try again
            if( skip.contains( templateName ) )
            {
                return false;
            }

            try
            {
                final Template template = cfg.getTemplate( templateName );
                Representation rep = new WriterRepresentation( MediaType.TEXT_HTML )
                {
                    @Override
                    public void write( Writer writer )
                        throws IOException
                    {
                        Map<String, Object> context = new HashMap<String, Object>();
                        context.put( "request", response.getRequest() );
                        context.put( "response", response );

                        context.put( "result", result );

                        try
                        {
                            template.process( context, writer );
                        }
                        catch( TemplateException e )
                        {
                            throw new IOException( e );
                        }
                    }
                };
                response.setEntity( rep );
                return true;
            }
            catch( Exception e )
            {
                skip.add( templateName );
                // Ignore
            }
        }
        return false;
    }
}