Retrieving a list of objects with their dependencies

In this recipe, we will add a DAO method to generate, from an SQL query joining several tables, a list of objects with their dependencies. We will retrieve a list of User objects along with their Post objects (blog posts written by these users).

Getting ready

You need to have model classes related to each other. In this example, a user has many posts:

public class User {
  private Long id;
  private String firstName;
  private Integer age;
  private LinkedList<Post> posts = new LinkedList<Post>();

public class Post {
  private long id;
  private String title;
  private Date date;
  private User user;

You need to have corresponding database tables, for example:

CREATE TABLE `user` (
  `id` int(11) AUTO_INCREMENT,
  `first_name` text,
  `age` int(11),
  PRIMARY KEY (`id`)
)

CREATE TABLE `post` (
  `id` int(11) AUTO_INCREMENT,
  `title` text,
  `date` datetime,
  `user_id` int(11),
  PRIMARY KEY (`id`),
  CONSTRAINT `user_id` FOREIGN...