Package org.geotools.util.factory

Class 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 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

      • 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

      • 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