src/com/google/wireless/gdata2/serializer/xml/XmlEntryGDataSerializer.java

// Copyright 2007 The Android Open Source Project

package com.google.wireless.gdata2.serializer.xml;

import com.google.wireless.gdata2.data.Entry;
import com.google.wireless.gdata2.data.ExtendedProperty;
import com.google.wireless.gdata2.data.StringUtils;
import com.google.wireless.gdata2.parser.ParseException;
import com.google.wireless.gdata2.parser.xml.XmlGDataParser;
import com.google.wireless.gdata2.parser.xml.XmlParserFactory;
import com.google.wireless.gdata2.serializer.GDataSerializer;

import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlSerializer;

import java.io.IOException;
import java.io.OutputStream;

/**
 * Serializes GData entries to the Atom XML format.
 */
public class XmlEntryGDataSerializer implements GDataSerializer {

  /** The XmlParserFactory that is used to create the XmlSerializer */
  private final XmlParserFactory factory;

  /** The entry being serialized. */
  private final Entry entry;

  /**
   * Creates a new XmlEntryGDataSerializer that will serialize the provided
   * entry.
   *
   * @param entry The entry that should be serialized.
   */
  public XmlEntryGDataSerializer(XmlParserFactory factory,
      Entry entry) {
    this.factory = factory;
    this.entry = entry;
  }

  /**
   * Returns the entry being serialized.
   * @return The entry being serialized.
   */
  protected Entry getEntry() {
    return entry;
  }

  /* (non-Javadoc)
  * @see GDataSerializer#getContentType()
  */
  public String getContentType() {
    return "application/atom+xml";
  }

  /* (non-Javadoc)
  * @see GDataSerializer#serialize(java.io.OutputStream)
  */
  public void serialize(OutputStream out, int format)
      throws IOException, ParseException {
    XmlSerializer serializer = null;
    try {
      serializer = factory.createSerializer();
    } catch (XmlPullParserException e) {
      throw new ParseException("Unable to create XmlSerializer.", e);
    }
    // TODO: make the output compact

    serializer.setOutput(out, "UTF-8");
    serializer.startDocument("UTF-8", new Boolean(false));

    declareEntryNamespaces(serializer);
    serializer.startTag(XmlGDataParser.NAMESPACE_ATOM_URI, "entry");

    serializeEntryContents(serializer, format);

    serializer.endTag(XmlGDataParser.NAMESPACE_ATOM_URI, "entry");
    serializer.endDocument();
    serializer.flush();
  }

  private final void declareEntryNamespaces(XmlSerializer serializer)
      throws IOException {
    serializer.setPrefix("" /* default ns */,
        XmlGDataParser.NAMESPACE_ATOM_URI);
    serializer.setPrefix(XmlGDataParser.NAMESPACE_GD,
        XmlGDataParser.NAMESPACE_GD_URI);
    declareExtraEntryNamespaces(serializer);
  }

  protected void declareExtraEntryNamespaces(XmlSerializer serializer)
      throws IOException {
    // no-op in this class
  }

  /**
   * @param serializer
   * @throws IOException
   */
  private final void serializeEntryContents(XmlSerializer serializer,
      int format)
      throws ParseException, IOException {

    if (format != FORMAT_CREATE) {
      serializeId(serializer, entry.getId());
    }

    serializeTitle(serializer, entry.getTitle());

    if (format != FORMAT_CREATE) {
      serializeLink(serializer, "edit" /* rel */, entry.getEditUri(), null /* type */, null /* etag */ );
      serializeLink(serializer, "alternate" /* rel */, entry.getHtmlUri(), "text/html" /* type */, null /* etag */ );
    }

    serializeSummary(serializer, entry.getSummary());

    serializeContent(serializer, entry.getContent());

    serializeAuthor(serializer, entry.getAuthor(), entry.getEmail());

    serializeCategory(serializer,
        entry.getCategory(), entry.getCategoryScheme());

    if (format == FORMAT_FULL) {
      serializePublicationDate(serializer,
          entry.getPublicationDate());
    }

    if (format != FORMAT_CREATE) {
      serializeUpdateDate(serializer,
          entry.getUpdateDate());
    }

    serializeExtraEntryContents(serializer, format);
  }

  /**
   * Hook for subclasses to serialize extra fields within the entry.
   * @param serializer The XmlSerializer being used to serialize the entry.
   * @param format The serialization format for the entry.
   * @throws ParseException Thrown if the entry cannot be serialized.
   * @throws IOException Thrown if the entry cannot be written to the
   * underlying {@link OutputStream}.
   */
  protected void serializeExtraEntryContents(XmlSerializer serializer,
      int format)
      throws ParseException, IOException {
    // no-op in this class.
  }

  // TODO: make these helper methods protected so sublcasses can use them?

  private static void serializeId(XmlSerializer serializer,
      String id) throws IOException {
    if (StringUtils.isEmpty(id)) {
      return;
    }
    serializer.startTag(null /* ns */, "id");
    serializer.text(id);
    serializer.endTag(null /* ns */, "id");
  }

  private static void serializeTitle(XmlSerializer serializer,
      String title)
      throws IOException {
    if (StringUtils.isEmpty(title)) {
      return;
    }
    serializer.startTag(null /* ns */, "title");
    serializer.text(title);
    serializer.endTag(null /* ns */, "title");
  }

  /**
   * Serializes a link relationship into the xml serializer passed in.
   * 
   * @param serializer The serializer to be used
   * @param rel        The relationship value (like alternate, edit etc)
   * @param href       the URI this link points to
   * @param type       the content type
   * @param etag       the optional etag if this link specifies a resource
   * 
   * @exception IOException
   */
  protected static void serializeLink(XmlSerializer serializer, String rel, String href, String type, String etag)
      throws IOException {
    if (StringUtils.isEmpty(href)) {
      return;
    }
    serializer.startTag(null /* ns */, "link");
    serializer.attribute(null /* ns */, "rel", rel);
    serializer.attribute(null /* ns */, "href", href);
    if (!StringUtils.isEmpty(type)) serializer.attribute(null /* ns */, "type", type);
    if (!StringUtils.isEmpty(etag)) serializer.attribute(null /* ns */, "etag", etag);
    serializer.endTag(null /* ns */, "link");
  }

  private static void serializeSummary(XmlSerializer serializer,
      String summary)
      throws IOException {
    if (StringUtils.isEmpty(summary)) {
      return;
    }
    serializer.startTag(null /* ns */, "summary");
    serializer.text(summary);
    serializer.endTag(null /* ns */, "summary");
  }

  private static void serializeContent(XmlSerializer serializer,
      String content)
      throws IOException {
    if (content == null) {
      return;
    }
    serializer.startTag(null /* ns */, "content");
    serializer.attribute(null /* ns */, "type", "text");
    serializer.text(content);
    serializer.endTag(null /* ns */, "content");
  }

  private static void serializeAuthor(XmlSerializer serializer,
      String author,
      String email)
      throws IOException {
    if (StringUtils.isEmpty(author) || StringUtils.isEmpty(email)) {
      return;
    }
    serializer.startTag(null /* ns */, "author");
    serializer.startTag(null /* ns */, "name");
    serializer.text(author);
    serializer.endTag(null /* ns */, "name");
    serializer.startTag(null /* ns */, "email");
    serializer.text(email);
    serializer.endTag(null /* ns */, "email");
    serializer.endTag(null /* ns */, "author");
  }

  private static void serializeCategory(XmlSerializer serializer,
      String category,
      String categoryScheme)
      throws IOException {
    if (StringUtils.isEmpty(category) &&
        StringUtils.isEmpty(categoryScheme)) {
      return;
    }
    serializer.startTag(null /* ns */, "category");
    if (!StringUtils.isEmpty(category)) {
      serializer.attribute(null /* ns */, "term", category);
    }
    if (!StringUtils.isEmpty(categoryScheme)) {
      serializer.attribute(null /* ns */, "scheme", categoryScheme);
    }
    serializer.endTag(null /* ns */, "category");
  }

  private static void
  serializePublicationDate(XmlSerializer serializer,
      String publicationDate)
      throws IOException {
    if (StringUtils.isEmpty(publicationDate)) {
      return;
    }
    serializer.startTag(null /* ns */, "published");
    serializer.text(publicationDate);
    serializer.endTag(null /* ns */, "published");
  }

  private static void
  serializeUpdateDate(XmlSerializer serializer,
      String updateDate)
      throws IOException {
    if (StringUtils.isEmpty(updateDate)) {
      return;
    }
    serializer.startTag(null /* ns */, "updated");
    serializer.text(updateDate);
    serializer.endTag(null /* ns */, "updated");
  }
}