Question

I saw this Java snippet in the book Spring in Action, but I’m not familiar with the language construct.

new RowMapper() {
  public Object mapRow() throws SQLException, DataAccessException {
    Motorist motorist = new Motorist();
    motorist.setId(rs.getInt(1));
    motorist.setEmail(rs.getString(2));
    motorist.setPassword(rs.getString(3));
    motorist.setFirstName(rs.getString(4));
    motorist.setLastName(rs.getString(5));
    return motorist;
  }
}

According the Spring documentation, RowMapper is an interface. It looks to me like an anonymous class definition based on the RowMapper interface. The new keyword is a little confusing, making me wonder if this also creates one instance of the anonymous class. I would guess yes, because if the class has no name, how will you ever create an instance after the line that defines it?

Can anyone confirm my guesses that:

• this is an anonymous class definition based on the RowMapper interface, and
• it creates a single instance of that class?

Answer 1

This is an anonymous class definition based on the RowMapper interface

That’s precisely what it is.

It creates a single instance of that class?

Yep. That’s correct.