org.glassfish.hk2
Interface ServiceLocator<T>

All Superinterfaces:

Providers<T>

All Known Subinterfaces:

ContractLocator<T>

public interface ServiceLocator<T>
extends Providers<T>

A ServiceLocator provides runtime access to a particular service in HK2.

At any point in time, one can get the Providers that qualify to the locator query by calling the super class methods.

There are two variations of ServiceLocators. The first type is when a ServiceLocator is produced by methods like Locator.byType(Class) and Locator.byType(String).

In HK2, services "byType" represent a concrete class type lacking any contract level abstraction of that concrete class as shown in this example:

 @Service
 public class Example {
  ...
 }
 

Services "byType" are either present or they are not. This is because a service "byType" is a concrete class declaration as shown in the example above. Example.class will either be present in the HK2 service registry or it will not. In another words, there is no further way to abstractly locate Example.class when it is being sought by its type.

The methods #getProvider() and {@link #get()} represent access to the singleton if the service "byType" exists in the HK2 service registry. If the service component does not exist then these methods will return null. In this situation, {@link #all()} will return an empty collection. Otherwise {@link #all} will return a singleton collection.

The second variation of ServiceLocator is that it forms the super interface for {@link ContractLocator} and is produced by methods like {@link Services#forContract(Class)} and {@link Services#forContract(String)}.

Unlike "byType" where there can either be zero or one manifestation of a qualifying service, a {@link ContractLocator} can represent many service instances in the HK2 service registry. In this case, the methods {@link #getProvider()} and {@link #get()} represent the "best qualifying" service matching the locator criteria.

See {@link ContractLocator} for more detail.

Author:

Jerome Dochez, Jeff Trent, Mason Taube

See Also:

ContractLocator

Method Summary

Methods inherited from interface org.glassfish.hk2.Providers

all, get, getProvider