Question

Can I have a factory as follows?

public class Factory
{
    private static Map<EnumXyz, IDAO> map = new HashMap<Sting, Object>();


    public static void init()
    {
        //how do i initialize my map through spring initialization
    }

    public static IDAO getDAO(EnumXyz dao)
    {
        if (map.containsKey(dao))
        return map.get(dao);
        else
        {
            throw new IllegalArgumentException("dao not supported " + dao);
        }

        return null;
    }

}

1. How do I take care of the initialization of my factory through spring?
2. Is this way of building a factory correct?
3. Any other, better approach?

Answer 1

I would instantiate your factory as a bean itself, and have an instance of it – don’t make everything static. Spring itself can control whether your bean is a singleton (it will default as such).

e.g.

public class Factory {
   public Factory(final Map<String,Object} map) {
      this.map = map;
   }
}

and your Spring config:

<bean id="myFactory" class="Factory">
   <constructor-arg>
      <util:map>
        <!-- configure your map here, or reference it as a separate bean -->
        <entry key="java.lang.String" value="key">....</entry>
      </util:map>
   </constructor-arg>
</bean>

In your constructor, pass in the map which is defined itself in your Spring config.