How to create relationships between objects in Spring JDBC?

Question

I want to implement relationships from JPA to Spring JDBC. For instance, assume I have Account and Advert objects. The relationship between Account and Advert is @OneToMany according to JPA.

Account class:

public class Account {

private Long id;
private String username;
private Set<Advert> adverts = new HashSet<Advert>();

// getters + setters
}

Advert class:

public class Advert {

private Long id;
private String text;
private Account account;

// getters + setters
}

AccountMapper:

public class AccountMapper implements RowMapper<Account> {

public Account mapRow(ResultSet rs, int rowNum) throws SQLException {
    Account account = new Account();
    account.setId(rs.getLong("id"));
    account.setUsername(rs.getString("username"));
    return account;
}
}

Now, I am trying to create a Mapper for the Advert class. How can I map the account variable from the Advert class to a row? Many thanks

Answer 1

Well if you do not use an ORM ... you have no object relation mapping ! After all the ORMs were created for that reason :-)

More seriously, ORM saves you from writing a lot of boilerplate code. Using direct JDBC instead of JPA is a code optimisation. Like any other code optimisation, it should be used when appropriate. It is relevant for :

• libraries using few tables that do not want to rely on an ORM (ex: user, roles, and ACL in spring security)
• identified bottlenecks in larger application

My advice should be to first use JPA or native hibernate hidden in a DAO layer. Then carefully analyze your performance problems and rewrite the most expensive parts in JDBC.

Of course, you can directly code you DAO implementations in JDBC, but it will be much longer to write.

I almost forgot the essential part : in an ORM you map classes and relations, in JDBC you write independant SQL queries.