Package 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:

  • Field Details

    • LOGGER

      protected static final Logger LOGGER
      The logger for all events related to factory registry.

  • Constructor Details

    • 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 Details

    • 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:

    • 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:

      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