GWT RPC: DTO vs. DAO?

Question

I've started learning GWT about a week ago and here's the question I can't answer for sure.

Here's the server-side:

// business object - has logic
interface Article {
  String getTitle(); // lazy
  void setTitle();
  String getText(); // lazy
  void setText();
  Set<Comment> getComments(); // lazy
}

// also has logic
interface Comment { ... }

I need to somehow create a GWT widget to visualize Article. Passing Article won't work, since it's not serializable and moreover, it has some BL. So, there are 2 ways:

The first one is to use DTOs like:

class ArticleDTO implements Serializable {
  public int articleId;
  public String title;
  public String text;
}

class CommentDTO implements Serializable {
  public int commentId;
  public int articleId;
  public String commentText;
}

The I'll have to implement a repository logic in my GWT RPC service:

class MyRPCRepository ... {
  ArticleDTO getArticle(int id);
  void saveArticle(ArticleDTO article);
  void deleteArticle(ArticleDTO article);
  ...similar things for comments here...
}

The second way is to use DAOs:

class ArticleDAO implements Serializable {
  private transitional MyRPC rpc;
  private int articleId; // only this one is serializable

  public ArticleDAO(MyRPC rpc, int articleId) { ... }

  public String getTitle() {
    // i know it would require more code in real
    return rpc.getArticleTitle(articleId);
  }
  ...
}

I like the first one, because it's really stupid. I like the second one because it's quite intellectual. Which one should I choose to make the code easier to understand and maintain?

Answer 1

In projects I've worked on, people seem to differ a lot in their opinions about the best approach to take with problems like this. There are pros and cons for both. The DTO approach is now supported by GWT in an API called RequestFactory, and is advertised as an alternative to "standard" GWT RPC usage (your DAO approach). You gain performance and integration with GWT's data binding framework, and the cost of maintaining the DTOs. I think it's a good trade-off, but for small projects it might be overkill.