private static String createEntryKey(
      final EntityInfoAggregator entityInfo, final Map<String, Object> data)
      throws EntityProviderException {
    final List<EntityPropertyInfo> keyPropertyInfos = entityInfo.getKeyPropertyInfos();

    StringBuilder keys = new StringBuilder();
    for (final EntityPropertyInfo keyPropertyInfo : keyPropertyInfos) {
      if (keys.length() > 0) {
        keys.append(',');
      }

      final String name = keyPropertyInfo.getName();
      if (keyPropertyInfos.size() > 1) {
        keys.append(Encoder.encode(name)).append('=');
      }

      final EdmSimpleType type = (EdmSimpleType) keyPropertyInfo.getType();
      try {
        keys.append(
            Encoder.encode(
                type.valueToString(
                    data.get(name), EdmLiteralKind.URI, keyPropertyInfo.getFacets())));
      } catch (final EdmSimpleTypeException e) {
        throw new EntityProviderException(EntityProviderException.COMMON, e);
      }
    }

    return keys.toString();
  }
  protected static String createSelfLink(
      final EntityInfoAggregator eia, final Map<String, Object> data, final String extension)
      throws EntityProviderException {
    StringBuilder sb = new StringBuilder();
    if (!eia.isDefaultEntityContainer()) {
      sb.append(Encoder.encode(eia.getEntityContainerName())).append(Edm.DELIMITER);
    }
    sb.append(Encoder.encode(eia.getEntitySetName()));

    sb.append("(")
        .append(createEntryKey(eia, data))
        .append(")")
        .append(extension == null ? "" : ("/" + extension));
    return sb.toString();
  }
  public void append(
      final Writer writer,
      final EntityInfoAggregator entityInfo,
      final Map<String, Object> data,
      final boolean isRootElement)
      throws EntityProviderException {
    final EdmEntityType type = entityInfo.getEntityType();

    try {
      jsonStreamWriter = new JsonStreamWriter(writer);
      if (isRootElement) {
        jsonStreamWriter.beginObject();
        jsonStreamWriter.name(FormatJson.D);
      }

      jsonStreamWriter.beginObject();

      jsonStreamWriter.name(FormatJson.METADATA);
      jsonStreamWriter.beginObject();
      final String self = AtomEntryEntityProducer.createSelfLink(entityInfo, data, null);
      location = properties.getServiceRoot().toASCIIString() + self;
      jsonStreamWriter.namedStringValue(FormatJson.ID, location);
      jsonStreamWriter.separator();
      jsonStreamWriter.namedStringValue(FormatJson.URI, location);
      jsonStreamWriter.separator();
      jsonStreamWriter.namedStringValueRaw(
          FormatJson.TYPE, type.getNamespace() + Edm.DELIMITER + type.getName());
      eTag = AtomEntryEntityProducer.createETag(entityInfo, data);
      if (eTag != null) {
        jsonStreamWriter.separator();
        jsonStreamWriter.namedStringValue(FormatJson.ETAG, eTag);
      }
      if (type.hasStream()) {
        jsonStreamWriter.separator();
        jsonStreamWriter.namedStringValueRaw(
            FormatJson.CONTENT_TYPE,
            properties.getMediaResourceMimeType() == null
                ? type.getMapping() == null || type.getMapping().getMimeType() == null
                    ? HttpContentType.APPLICATION_OCTET_STREAM
                    : data.get(type.getMapping().getMimeType()).toString()
                : properties.getMediaResourceMimeType());
        jsonStreamWriter.separator();
        jsonStreamWriter.namedStringValue(FormatJson.MEDIA_SRC, self + "/$value");
        jsonStreamWriter.separator();
        jsonStreamWriter.namedStringValue(FormatJson.EDIT_MEDIA, location + "/$value");
      }
      jsonStreamWriter.endObject();

      for (final String propertyName : type.getPropertyNames()) {
        if (entityInfo.getSelectedPropertyNames().contains(propertyName)) {
          jsonStreamWriter.separator();
          jsonStreamWriter.name(propertyName);
          JsonPropertyEntityProducer.appendPropertyValue(
              jsonStreamWriter, entityInfo.getPropertyInfo(propertyName), data.get(propertyName));
        }
      }

      for (final String navigationPropertyName : type.getNavigationPropertyNames()) {
        if (entityInfo.getSelectedNavigationPropertyNames().contains(navigationPropertyName)) {
          jsonStreamWriter.separator();
          jsonStreamWriter.name(navigationPropertyName);
          if (entityInfo.getExpandedNavigationPropertyNames().contains(navigationPropertyName)) {
            if (properties.getCallbacks() != null
                && properties.getCallbacks().containsKey(navigationPropertyName)) {
              final EdmNavigationProperty navigationProperty =
                  (EdmNavigationProperty) type.getProperty(navigationPropertyName);
              final boolean isFeed = navigationProperty.getMultiplicity() == EdmMultiplicity.MANY;
              final EdmEntitySet entitySet = entityInfo.getEntitySet();
              final EdmEntitySet inlineEntitySet =
                  entitySet.getRelatedEntitySet(navigationProperty);

              WriteCallbackContext context =
                  isFeed ? new WriteFeedCallbackContext() : new WriteEntryCallbackContext();
              context.setSourceEntitySet(entitySet);
              context.setNavigationProperty(navigationProperty);
              context.setEntryData(data);
              context.setCurrentExpandSelectTreeNode(
                  properties.getExpandSelectTree().getLinks().get(navigationPropertyName));

              ODataCallback callback = properties.getCallbacks().get(navigationPropertyName);
              try {
                if (isFeed) {
                  final WriteFeedCallbackResult result =
                      ((OnWriteFeedContent) callback)
                          .retrieveFeedResult((WriteFeedCallbackContext) context);
                  List<Map<String, Object>> inlineData = result.getFeedData();
                  if (inlineData != null) {
                    final EntityProviderWriteProperties inlineProperties =
                        result.getInlineProperties();
                    final EntityInfoAggregator inlineEntityInfo =
                        EntityInfoAggregator.create(
                            inlineEntitySet, inlineProperties.getExpandSelectTree());
                    new JsonFeedEntityProducer(inlineProperties)
                        .append(writer, inlineEntityInfo, inlineData, false);
                  }
                } else {
                  final WriteEntryCallbackResult result =
                      ((OnWriteEntryContent) callback)
                          .retrieveEntryResult((WriteEntryCallbackContext) context);
                  Map<String, Object> inlineData = result.getEntryData();
                  if (inlineData != null) {
                    final EntityProviderWriteProperties inlineProperties =
                        result.getInlineProperties();
                    final EntityInfoAggregator inlineEntityInfo =
                        EntityInfoAggregator.create(
                            inlineEntitySet, inlineProperties.getExpandSelectTree());
                    new JsonEntryEntityProducer(inlineProperties)
                        .append(writer, inlineEntityInfo, inlineData, false);
                  }
                }
              } catch (final ODataApplicationException e) {
                throw new EntityProviderException(EntityProviderException.COMMON, e);
              }
            } else {
              throw new EntityProviderException(
                  EntityProviderException.EXPANDNOTSUPPORTED.addContent(navigationPropertyName));
            }
          } else {
            jsonStreamWriter.beginObject();
            jsonStreamWriter.name(FormatJson.DEFERRED);
            JsonLinkEntityProducer.appendUri(
                jsonStreamWriter, location + "/" + Encoder.encode(navigationPropertyName));
            jsonStreamWriter.endObject();
          }
        }
      }

      jsonStreamWriter.endObject();

      if (isRootElement) {
        jsonStreamWriter.endObject();
      }

    } catch (final IOException e) {
      throw new EntityProviderException(EntityProviderException.COMMON, e);
    } catch (final EdmException e) {
      throw new EntityProviderException(EntityProviderException.COMMON, e);
    }
  }