Package org.elasticsearch.common.inject

Interface Binding<T>

Type Parameters:
T - the bound type. The injected is always assignable to this type.
All Superinterfaces:
Element
All Known Subinterfaces:
ConstructorBinding<T>, ConvertedConstantBinding<T>, ExposedBinding<T>, InstanceBinding<T>, LinkedKeyBinding<T>, ProviderBinding<T>, ProviderInstanceBinding<T>, ProviderKeyBinding<T>, UntargettedBinding<T>
All Known Implementing Classes:
BindingImpl, ExposedBindingImpl, InstanceBindingImpl, LinkedBindingImpl, LinkedProviderBindingImpl, ProviderInstanceBindingImpl, UntargettedBindingImpl
public interface Binding<T>
extends Element
A mapping from a key (type and optional annotation) to the strategy for getting instances of the type. This interface is part of the introspection API and is intended primarily for use by tools.

Bindings are created in several ways:

  • Explicitly in a module, via bind() and bindConstant() statements: 
         bind(Service.class).annotatedWith(Red.class).to(ServiceImpl.class);
     bindConstant().annotatedWith(ServerHost.class).to(args[0]);
  • Implicitly by the Injector by following a type's pointer annotations or by using its annotated or default constructor.
  • By converting a bound instance to a different type.
  • For providers, by delegating to the binding for the provided type.

They exist on both modules and on injectors, and their behaviour is different for each:

  • Module bindings are incomplete and cannot be used to provide instances. This is because the applicable scopes and interceptors may not be known until an injector is created. From a tool's perspective, module bindings are like the injector's source code. They can be inspected or rewritten, but this analysis must be done statically.
  • Injector bindings are complete and valid and can be used to provide instances. From a tools' perspective, injector bindings are like reflection for an injector. They have full runtime information, including the complete graph of injections necessary to satisfy a binding.