guice绑定到实例和asEagersingleton有什么区别

Question

When we do a

bind(ClassName).toInstance(new ClassName()) inside the configure method do we essentially mean that it is an "eagerly initialized singleton" by default?

If yes, what is the use of adding

bind(ClassName).toInstance(new ClassName()).asEagerSingleton()

Answer 1

It's not possible to append .asEagerSingleton()

The complete signature of toInstance is the following:

void toInstance(T instance)

Since toInstance(T) returns nothing, you can't chain it with .asEagerSingleton() . The compilation will fail if you do that.

As you suspected, toInstance is already an eagerly-loaded singleton, this is why it's a chain-ending method ( void ) and not a binding declaration that can be further scoped.