net.java.truecommons.services

Class ServiceLocator

java.lang.Object

net.java.truecommons.services.ServiceLocator

@Immutable
public final class ServiceLocator
extends Object

Creates containers or factories of products. Resolving service instances is done in several steps:

First, the name of a given provider service class is used as the key string to lookup a system property. If this yields a value then it's supposed to name a class which gets loaded and instantiated by calling its public no-argument constructor.

Otherwise, the class path is searched for any resources with the name "META-INF/services/" plus the name of the given locatable provider class. If this yields no results, a ServiceConfigurationError is thrown.

Otherwise the classes with the names contained in these resources get loaded and instantiated by calling their public no-argument constructor. Next, the instances are filtered according to their priority. Only the instance with the highest priority is kept for subsequent use.

Next, the class is searched again for any resources with the name "META-INF/services/" plus the name of the given locatable function class. If this yields some results, the classes with the names contained in these resources get loaded and instantiated by calling their public no-argument constructor. Next, the instances get sorted in ascending order of their priority and kept for subsequent use.

Finally, depending on the requesting method either a container or a factory gets created which will use the instantiated provider and functions to obtain a product and map it in order of their priorities.

Author:

Christian Schlichtherle

See Also:

ServiceLoader

Constructor Summary

Constructors

Constructor and Description
ServiceLocator(Class<?> client) Constructs a new locator which uses the class loader of the given client class before using the current thread context's class loader unless the latter is identical to the former.
ServiceLocator(ClassLoader loader) Constructs a new locator which uses the given class loader before using the current thread context's class loader unless the latter is identical to the former.

Method Summary

Modifier and Type	Method and Description
<P> Container<P>	container(Class<? extends LocatableProvider<P>> provider) Creates a new container with a single product.
<P> Container<P>	container(Class<? extends LocatableProvider<P>> provider, Class<? extends LocatableDecorator<P>> decorator) Creates a new container with a single product.
<P> Factory<P>	factory(Class<? extends LocatableFactory<P>> factory) Creates a new factory for products.
<P> Factory<P>	factory(Class<? extends LocatableFactory<P>> factory, Class<? extends LocatableFunction<P>> functions) Creates a new factory for products.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ServiceLocator

public ServiceLocator(Class<?> client)

Constructs a new locator which uses the class loader of the given client class before using the current thread context's class loader unless the latter is identical to the former.

Parameters:

client - the class which identifies the calling client.

ServiceLocator

public ServiceLocator(ClassLoader loader)

Constructs a new locator which uses the given class loader before using the current thread context's class loader unless the latter is identical to the former.

Parameters:

loader - the class loader to use before the current thread context's class loader unless the the latter is identical to the former.

Since:

TrueCommons 1.0.13

Method Detail

container

public <P> Container<P> container(Class<? extends LocatableProvider<P>> provider)
                           throws ServiceConfigurationError

Creates a new container with a single product.

Type Parameters:

P - the type of the product to contain.

Parameters:

provider - the class of the locatable provider for the product.

Returns:

A new container with a single product.

Throws:

ServiceConfigurationError - if loading or instantiating a located class fails for some reason.

container

public <P> Container<P> container(Class<? extends LocatableProvider<P>> provider,
                                  @Nullable
                                  Class<? extends LocatableDecorator<P>> decorator)
                           throws ServiceConfigurationError

Creates a new container with a single product.

Type Parameters:

P - the type of the product to contain.

Parameters:

provider - the class of the locatable provider for the product.

decorator - the class of the locatable decoractors for the product.

Returns:

A new container with a single product.

Throws:

ServiceConfigurationError - if loading or instantiating a located class fails for some reason.

factory

public <P> Factory<P> factory(Class<? extends LocatableFactory<P>> factory)
                       throws ServiceConfigurationError

Creates a new factory for products.

Type Parameters:

P - the type of the products to create.

Parameters:

factory - the class of the locatable factory for the products.

Returns:

A new factory of products.

Throws:

ServiceConfigurationError - if loading or instantiating a located class fails for some reason.

factory

public <P> Factory<P> factory(Class<? extends LocatableFactory<P>> factory,
                              @Nullable
                              Class<? extends LocatableFunction<P>> functions)
                       throws ServiceConfigurationError

Creates a new factory for products.

Type Parameters:

P - the type of the products to create.

Parameters:

factory - the class of the locatable factory for the products.

functions - the class of the locatable functions for the products.

Returns:

A new factory of products.

Throws:

ServiceConfigurationError - if loading or instantiating a located class fails for some reason.