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 * and Distribution License("CDDL") (collectively, the "License").  You
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package com.sun.jersey.atom.abdera;

import com.sun.jersey.core.util.MultivaluedMapImpl;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.lang.annotation.Annotation;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyReader;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Providers;
import org.apache.abdera.Abdera;
import org.apache.abdera.model.Document;
import org.apache.abdera.model.Element;
import org.apache.abdera.model.Entry;
import org.apache.abdera.parser.Parser;

/**
 * Helper class to assist in serializing and deserializing Java entities
 * as XML that will be transferred through the content element
 * of an Atom Entry instance.  A configured instance of this
 * class can be made available in a resource class as follows:
 *
 *  *   @Context
 *   private ContentHelper contentHelper;
 *


 */
public class ContentHelper {


    // ------------------------------------------------------------ Constructors


    /**
     * Construct a configured instance of this helper.
     *
     * @param providers Providers for this application
     */
    public ContentHelper(Providers providers) {
        this.providers = providers;
    }


    // ------------------------------------------------------ Instance Variables


    /**
     * 
Singleton Abdera instance for this application.
     */
    private Abdera abdera = Abdera.getInstance();


    /**
     * Empty array of annotations for calls to message body readers and writers.
     */
    private Annotation[] emptyAnnotations = new Annotation[0];


    /**
     * Empty map of headers for calls to message body readers and writers.
     */
    private MultivaluedMap emptyHeaders = new MultivaluedMapImpl();


    /**
     * The injected helper to look up appropriate Provider
     * instances.
     */
    private Providers providers;


    // ---------------------------------------------------------- Public Methods


    /**
     * Deserialize the content element of the specified entry, and
     * transform it back into an appropriate Java object.  The media type
     * used for selecting an appropriate Provider will be
     * acquired from the type attribute of the content
     * element.
     *
     * @param entry Entry whose content element is to be processed
     * @param clazz Class of the object to be returned
     *
     * @exception IllegalArgumentException if the specified entry does not
     *  contain a valid content element
     */
    public  T getContentEntity(Entry entry, Class clazz) {
        String[] parts = entry.getContentMimeType().toString().split("/");
        if (parts.length != 2) {
            throw new IllegalArgumentException("Invalid content type '" + entry.getContentMimeType().toString() + "'");
        }
        return getContentEntity(entry, new MediaType(parts[0], parts[1]), clazz);
    }


    /**
     * Deserialize the content element of the specified entry, and
     * transform it back into an appropriate Java object.
     *
     * @param entry Entry whose content element is to be processed
     * @param mediaType MediaType to use when selecting an
     *  appropriate provider
     * @param clazz Class of the object to be returned
     *
     * @exception IllegalArgumentException if the specified entry does not
     *  contain a valid content element
     */
    public  T getContentEntity(Entry entry, MediaType mediaType, Class clazz) {

        // Select the MessageBodyReader we will use
        MessageBodyReader reader =
          providers.getMessageBodyReader(clazz, clazz, emptyAnnotations, mediaType);
        if (reader == null) {
            throw new IllegalArgumentException
              ("No MessageBodyReader for class '" +
               clazz.getName() + "' and media type '" + mediaType + "'");
        }

        // Extract the content element as an XML byte stream
        if ((entry.getContentElement() == null) || (entry.getContentElement().getValueElement() == null)) {
            throw new IllegalArgumentException("Entry does not contain a valid content element");
        }
        Element element = entry.getContentElement().getValueElement();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            element.writeTo(baos);
        } catch (IOException e) {
            // Can not happen
        }

        // Transform the byte stream into an appropriate Java object
        try {
            return reader.readFrom(clazz, clazz, emptyAnnotations,
                                   mediaType, emptyHeaders,
                                   new ByteArrayInputStream(baos.toByteArray()));
        } catch (IOException e) {
            // Can not happen
            return null;
        }

    }


    /**
     * Serialize the specified entity as the content element
     * of the specified entry.  The selected provider MUST
     * produce an XML representation.
     *
     * @param entry Entry whose content element is to be set
     * @param mediaType MediaType to pass as the type
     *  attribute of the content element (also used to select an
     *  appropriate Provider)
     * @param entity Entity to be serialized
     */
    public void setContentEntity(Entry entry, MediaType mediaType, Object entity) {

        // Select the MessageBodyWriter we will use
        MessageBodyWriter writer =
          providers.getMessageBodyWriter(entity.getClass(),
                                         entity.getClass(),
                                         emptyAnnotations,
                                         mediaType);
        if (writer == null) {
            throw new IllegalArgumentException
              ("No MessageBodyWriter for class '" +
               entity.getClass().getName() + "' and media type '" + mediaType + "'");
        }

        // Serialize this entity to a byte stream
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            writer.writeTo(entity, entity.getClass(), entity.getClass(),
                           emptyAnnotations, mediaType, emptyHeaders, baos);
        } catch (IOException e) {
            // Can not happen
        }

        // Parse the XML into an Abdera Element (yes, this is pretty smelly)
        // and set it as the content element
        Parser parser = abdera.getParser();
        Document document = parser.parse(new ByteArrayInputStream(baos.toByteArray()));
        entry.setContent(document.getRoot(), mediaType.toString());

    }


}