Singleton?

[lviggiano]

Provide a way to define a singleton Config objects instead of creating new instances at every create() request.

3 possible ways:

1. Provide a @Singleton annotation
2. Provide a ConfigFactory.getInstance() method
3. Nothing. It's a problem of IoC and as that should be solved.

Also provide an example (on a new examples mvn module) to show how to instantiate singleton objects with Spring. See also http://forum.spring.io/forum/spring-projects/container/48256-using-factory-beans-with-factory-method-parameters

[gembin]

@Singleton +1
option 3 -1, not necessary to use a IoC framework always, i.e. foundation libraries

[lviggiano]

IoC can be done without any framework.

[gembin]

what i mean is that there are many cases without using IoC. : - )

[lviggiano]

Hi @gembin

I come out with an implementation of a sort of singleton, that actually is a cache of Config classes.

Before you used ConfigFactory:

    MyConfig instance = ConfigFactory.create(MyConfig.class);

The same way you can use the new ConfigCache:

    MyConfig instance = ConfigCache.getOrCreate(MyConfig.class);

The difference is that, when using ConfigFactory a new instance of the Config object is created every time, while using the ConfigCache, instances are returned from an internal cache.

    MyConfig firstFromFactory = ConfigFactory.create(MyConfig.class);
    MyConfig secondFromFactory = ConfigFactory.create(MyConfig.class); 
    // firstFromFactory not same as secondFromFactory

    MyConfig firstFromCache = ConfigCache.getOrCreate(MyConfig.class);
    MyConfig secondFromCache = ConfigCache.getOrCreate(MyConfig.class);
    // firstFromCache same as secondFromCache  

You can assign an "id" to an instance,

    MyConfig firstFromCache = ConfigCache.getOrCreate("foo", MyConfig.class);
    MyConfig secondFromCache = ConfigCache.getOrCreate("foo", MyConfig.class);
    MyConfig thirdFromCache = ConfigCache.getOrCreate("bar", MyConfig.class);
    // firstFromCache same as secondFromCache  
    // thirdFromCache not same as secodFromCache or firstFromCache

The ConfigCache is designed to be thread safe.

[lviggiano]

TODO-list before closing this issue:

• documentation

[gembin]

Great, thx!

[lviggiano]

Thanks to you for your help. I'll document this and the other improvements and cut a release asap, so you won't need to build the jar from a snapshot.

[lviggiano]

Documented http://owner.aeonbits.org/docs/singleton/