Preventing non-Singleton use outside of Spring

[hay7777]

Hi,

I have a DAO which I proxy and set up with an Interceptor using Spring.

However, there are no guarantees that Spring will be used everywhere the class is used.

I would normally force the DAO to be a singleton by using a private constructor with a getInstance(). How can I set this up so that Spring can create it as a Singleton, and everyone else have to use the getInstance()?

Cheers,

David

[irbouho]

You can configure a singleton class as a factory bean within Spring using the following:

  <bean name="myDAO"
            factory-method="getInstance"
            class="com.company.MyDAO" />

now back to your initial problem:
I do not think refactoring your DAO into a singleton will solve your problem unless you apply your Interceptor by code in the getInstance method. Otherwise, calling MyDAO.getInstance() will return an instance that is not proxied by your Interceptor.

[hay7777]

Thanks. I think that will be fine just making it a singleton and setting it as a factory bean.

If it's used outside of spring then the interceptor (handles transactions) won't be used.

[Rod Johnson]

Spring 1.1 should be able to invoke your private constructor, so you can stick with the previous getInstance() approach. Though of course Spring will be creating a new instance, subverting the Singleton usage pattern getInstance() implies. This may bother you more than it bothers me...