org.geotools.util.factory

Class FactoryRegistry

Object

FactoryRegistry

Direct Known Subclasses:

AnnotatedBeanProcessFactory.BeanFactoryRegistry, FactoryCreator

public class FactoryRegistry
extends Object

A registry for factories, organized by categories (usually by interface). For example CRSFactory.class is a category, and MathTransformFactory.class is another category.

For each category, implementations are registered in a file placed in the META-INF/services/ directory, as specified in the CategoryRegistry javadoc. Those files are usually bundled into the JAR file distributed by the vendor. If the same META-INF/services/ file appears many time in different JARs, they are processed as if their content were merged.

Example use:

 
 Set<Class<?>> categories =
     Collections.singleton(new Class<?>[] {
         MathTransformProvider.class
     });
 FactoryRegistry registry = new FactoryRegistry(categories);

 // get the factories
 Predicate filter = null;
 Hints hints = null;
 Iterator<MathTransform> providers =
     registry.getFactories(MathTransformProvider.class, null, hints);
 
 

NOTE: This class is not thread safe. Users are responsible for synchronisation. This is usually done in an utility class wrapping this factory registry (e.g. ReferencingFactoryFinder).

NOTE: Java 9 Service Registry Incompatibility. Prior releases of GeoTools uses Java's built-in ServiceRegistry to manage instances for our plug-in system. In Java 9 the service registry was restricted to a limited number of imageio services and was no longer available for general use. We have introduced CategoryRegistry to take over instance management, in conjunction with the supported ServiceLoader discovery.

Since:

2.1

Author:

Martin Desruisseaux, Richard Gould, Jody Garnett

See Also:

ReferencingFactoryFinder, CoverageFactoryFinder

Field Summary

Fields

Modifier and Type	Field and Description
protected static Logger	LOGGER The logger for all events related to factory registry.

Constructor Summary

Constructors

Constructor and Description
FactoryRegistry(Class<?>... categories) Constructs a new registry for the specified categories.
FactoryRegistry(Class<?> category) Constructs a new registry for the specified category.
FactoryRegistry(Collection<Class<?>> categories) Constructs a new registry for the specified categories.

Method Summary

Modifier and Type	Method and Description
void	deregisterAll() Clear all registered factories.
void	deregisterAll(Class<?> category) Clear registered factories for a provided category.
void	deregisterFactories(Iterable<?> factories) Manually deregister factories.
void	deregisterFactories(Iterator<?> factories) Manually deregister factories.
void	deregisterFactory(Object factory) Manually deregister a factory Used to facilitate integration with other plug-in systems, such as OSGi or Spring, that block CLASSPATH visibility of ServiceLoader implementation registration.
<T> boolean	deregisterFactory(T factory, Class<T> category) Manually deregister a factory Used to facilitate integration with other plug-in systems, such as OSGi or Spring, that block CLASSPATH visibility of ServiceLoader implementation registration.
protected void	finalize()
Set<ClassLoader>	getClassLoaders() Returns all class loaders to be used for scanning plugins.
<T> Stream<T>	getFactories(Class<T> category, boolean useOrdering) Factories for the provided category type.
<T> Stream<T>	getFactories(Class<T> category, Predicate<? super T> factoryFilter, boolean useOrdering) Factories for the provided category type.
<T> Stream<T>	getFactories(Class<T> category, Predicate<? super T> filter, Hints hints) Returns the factories in the registry for the specified category, filter and hints.
<T> T	getFactory(Class<T> category, Predicate<? super T> filter, Hints hints, Hints.Key key) Returns the first factory in the registry for the specified category, using the specified map of hints (if any).
<T> T	getFactoryByClass(Class<T> category) Instance of category, or null if not available.
protected <T> boolean	isAcceptable(T factory, Class<T> category, Hints hints) Returns true if the specified factory meets the requirements specified by a map of hints.
void	registerFactories(Iterable<?> factories) Manually register factories.
void	registerFactories(Iterator<?> factories) Manually register factories.
void	registerFactory(Object factory) Manually register a factory.
<T> boolean	registerFactory(T factory, Class<T> category) Manually register a factory.
void	scanForPlugins() Scans for factory plug-ins on the application class path.
<T> boolean	setOrdering(Class<T> base, boolean set, Predicate<? super T> filter1, Predicate<? super T> filter2) Sets or unsets a pairwise ordering between all factories meeting a criterion.
<T> boolean	setOrdering(Class<T> category, Comparator<T> comparator) Set pairwise ordering between all factories according a comparator.
<T> boolean	setOrdering(Class<T> category, T firstFactory, T secondFactory) Define pairwise ordering giving priority to the firstFactory over the secondFactory.
Stream<Class<?>>	streamCategories()
<T> boolean	unsetOrdering(Class<T> category, T firstFactory, T secondFactory) Removes the ordering between the specified factories, so that the first no longer appears before the second.

Methods inherited from class Object

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

Field Detail

LOGGER

protected static final Logger LOGGER

The logger for all events related to factory registry.

Constructor Detail

FactoryRegistry

public FactoryRegistry(Class<?> category)

Constructs a new registry for the specified category.

Parameters:

category - The single category.

Since:

2.4

FactoryRegistry

public FactoryRegistry(Class<?>... categories)

Constructs a new registry for the specified categories.

Parameters:

categories - The categories.

Since:

2.4

FactoryRegistry

public FactoryRegistry(Collection<Class<?>> categories)

Constructs a new registry for the specified categories.

Parameters:

categories - The categories.

Method Detail

finalize

protected void finalize()
                 throws Throwable

Overrides:

finalize in class Object

Throws:

Throwable

streamCategories

public Stream<Class<?>> streamCategories()

getFactoryByClass

public <T> T getFactoryByClass(Class<T> category)

Instance of category, or null if not available.

Parameters:

category - The category to look for. Usually an interface class (not the actual implementation class).

Returns:

instance, or null of not available

Since:

19

getFactories

public <T> Stream<T> getFactories(Class<T> category,
                                  boolean useOrdering)

Factories for the provided category type.

Parameters:

category - The category to look for. Usually an interface class (not the actual implementation class).

useOrdering - true to use provided pairwise orderings

Returns:

factories registered for category

Since:

19

getFactories

public <T> Stream<T> getFactories(Class<T> category,
                                  Predicate<? super T> factoryFilter,
                                  boolean useOrdering)

Factories for the provided category type.

Parameters:

category - The category to look for. Usually an interface class (not the actual implementation class).

factoryFilter - Predicate to filter factories, null for all factories

useOrdering - true to use provided pairwise orderings

Returns:

factories registered for category

Since:

19

getFactories

public <T> Stream<T> getFactories(Class<T> category,
                                  Predicate<? super T> filter,
                                  Hints hints)

Returns the factories in the registry for the specified category, filter and hints. Factories that are not available will be ignored. This method will scan for plugins the first time it is invoked for the given category.

Type Parameters:

T - The class represented by the category argument.

Parameters:

category - The category to look for. Usually an interface class (not the actual implementation class).

filter - The optional filter predicate, or null.

hints - The optional user requirements, or null.

Returns:

Factories ready to use for the specified category, filter and hints.

Since:

19

getFactory

public <T> T getFactory(Class<T> category,
                        Predicate<? super T> filter,
                        Hints hints,
                        Hints.Key key)
                 throws FactoryRegistryException

Returns the first factory in the registry for the specified category, using the specified map of hints (if any). This method may scan for plugins the first time it is invoked. Except as a result of this scan, no new factory instance is created by the default implementation of this method. The FactoryCreator class change this behavior however.

Type Parameters:

T - The class represented by the category argument.

Parameters:

category - The category to look for. Must be one of the categories declared to the constructor. Usually an interface class (not the actual implementation class).

filter - An optional filter, or null if none. This is used for example in order to select the first factory for some authority.

hints - A map of hints, or null if none.

key - The key to use for looking for a user-provided instance in the hints, or null if none.

Returns:

A factory available for use for the specified category and hints. The returns type is Object instead of Factory because the factory implementation doesn't need to be a Geotools one.

Throws:

FactoryNotFoundException - if no factory was found for the specified category, filter and hints.

FactoryRegistryException - if a factory can't be returned for some other reason.

See Also:

getFactories(Class, Predicate, Hints), FactoryCreator.getFactory(java.lang.Class<T>, java.util.function.Predicate<? super T>, org.geotools.util.factory.Hints, org.geotools.util.factory.Hints.Key)

isAcceptable

protected <T> boolean isAcceptable(T factory,
                                   Class<T> category,
                                   Hints hints)

Returns true if the specified factory meets the requirements specified by a map of hints.

The default implementation always returns true. There is no need to override this method for AbstractFactory implementations, since their hints are automatically checked.

Override this method for non-Geotools implementations. For example a JTS geometry factory finder may overrides this method in order to check if a GeometryFactory uses the required CoordinateSequenceFactory. Such method should be implemented as below, since this method may be invoked for various kind of objects:

 
 if (provider instanceof GeometryFactory) {
     // ... Check the GeometryFactory state here.
 }
 
 

Type Parameters:

T - The class represented by the category argument.

Parameters:

factory - The factory to checks.

category - The factory category. Usually an interface.

hints - The user requirements, or null if none.

Returns:

true if the provider meets the user requirements.

getClassLoaders

public final Set<ClassLoader> getClassLoaders()

Returns all class loaders to be used for scanning plugins. Current implementation returns the following class loaders:

• This object class loader
• The thread context class loader
• The system class loader

The actual number of class loaders may be smaller if redundancies was found. If some more classloaders should be scanned, they shall be added into the code of this method.

Returns:

All classloaders to be used for scanning plugins.

scanForPlugins

public void scanForPlugins()

Scans for factory plug-ins on the application class path. This method is needed because the application class path can theoretically change, or additional plug-ins may become available. Rather than re-scanning the classpath on every invocation of the API, the class path is scanned automatically only on the first invocation. Clients can call this method to prompt a re-scan. Thus this method need only be invoked by sophisticated applications which dynamically make new plug-ins available at runtime.

registerFactories

public void registerFactories(Iterator<?> factories)

Manually register factories.

Used to facilitate integration with other plug-in systems, such as OSGi or Spring, that block CLASSPATH visibility of ServiceLoader implementation registration.

registerFactories

public void registerFactories(Iterable<?> factories)

Manually register factories.

Used to facilitate integration with other plug-in systems, such as OSGi or Spring, that block CLASSPATH visibility of ServiceLoader implementation registration.

registerFactory

public void registerFactory(Object factory)

Manually register a factory.

Used to facilitate integration with other plug-in systems, such as OSGi or Spring, that block CLASSPATH visibility of ServiceLoader implementation registration.

registerFactory

public <T> boolean registerFactory(T factory,
                                   Class<T> category)

Manually register a factory.

Used to facilitate integration with other plug-in systems, such as OSGi or Spring, that block CLASSPATH visibility of ServiceLoader implementation registration.

deregisterAll

public void deregisterAll()

Clear all registered factories.

deregisterAll

public void deregisterAll(Class<?> category)

Clear registered factories for a provided category.

deregisterFactories

public void deregisterFactories(Iterator<?> factories)

Manually deregister factories.

Used to facilitate integration with other plug-in systems, such as OSGi or Spring, that block CLASSPATH visibility of ServiceLoader implementation registration.

deregisterFactories

public void deregisterFactories(Iterable<?> factories)

Manually deregister factories.

Used to facilitate integration with other plug-in systems, such as OSGi or Spring, that block CLASSPATH visibility of ServiceLoader implementation registration.

deregisterFactory

public void deregisterFactory(Object factory)

Manually deregister a factory

Used to facilitate integration with other plug-in systems, such as OSGi or Spring, that block CLASSPATH visibility of ServiceLoader implementation registration.

deregisterFactory

public <T> boolean deregisterFactory(T factory,
                                     Class<T> category)

Manually deregister a factory

Used to facilitate integration with other plug-in systems, such as OSGi or Spring, that block CLASSPATH visibility of ServiceLoader implementation registration.

setOrdering

public <T> boolean setOrdering(Class<T> category,
                               T firstFactory,
                               T secondFactory)

Define pairwise ordering giving priority to the firstFactory over the secondFactory.

Returns:

if this call establishes a new order

setOrdering

public <T> boolean setOrdering(Class<T> category,
                               Comparator<T> comparator)

Set pairwise ordering between all factories according a comparator. Calls to compare(factory1, factory2) should returns:

• -1 if factory1 is preferred to factory2
• +1 if factory2 is preferred to factory1
• 0 if there is no preferred order between factory1 and factory2

Type Parameters:

T - The class represented by the category argument.

Parameters:

category - The category to set ordering.

comparator - The comparator to use for ordering.

Returns:

true if at least one ordering setting has been modified as a consequence of this call.

setOrdering

public <T> boolean setOrdering(Class<T> base,
                               boolean set,
                               Predicate<? super T> filter1,
                               Predicate<? super T> filter2)

Sets or unsets a pairwise ordering between all factories meeting a criterion.

For example in the CRS framework (org.geotools.referencing.FactoryFinder), this is used for setting ordering between all factories provided by two vendors, or for two authorities. If one or both factories are not currently registered, or if the desired ordering is already set/unset, nothing happens and false is returned.

Type Parameters:

T - The class represented by the base argument.

Parameters:

base - The base category. Only categories assignable to base will be processed.

set - true for setting the ordering, or false for unsetting.

filter1 - Predicate for the preferred factory.

filter2 - Predicate for the factory to which filter1 is preferred.

Returns:

true if the ordering changed as a result of this call.

unsetOrdering

public <T> boolean unsetOrdering(Class<T> category,
                                 T firstFactory,
                                 T secondFactory)

Removes the ordering between the specified factories, so that the first no longer appears before the second.

Parameters:

category - The category to clear instance order for.

Returns:

true if that ordering was previously defined