/**
* Returns the first provider in the registry for the specified category, using the specified map
* of hints (if any). This method may {@linkplain #scanForPlugins scan for plugins} the first time
* it is invoked. Except as a result of this scan, no new provider instance is created by the
* default implementation of this method. The {@link FactoryCreator} class change this behavior
* however.
*
* @param <T> The class represented by the {@code category} argument.
* @param 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).
* @param filter An optional filter, or {@code null} if none. This is used for example in order to
* select the first factory for some {@linkplain
* org.opengis.referencing.AuthorityFactory#getAuthority authority}.
* @param hints A {@linkplain Hints map of hints}, or {@code null} if none.
* @param key The key to use for looking for a user-provided instance in the hints, or {@code
* null} if none.
* @return A factory {@linkplain OptionalFactory#isAvailable available} for use for the specified
* category and hints. The returns type is {@code Object} instead of {@link 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.
* @throws FactoryRegistryException if a factory can't be returned for some other reason.
* @see #getServiceProviders(Class, Filter, Hints)
* @see FactoryCreator#getServiceProvider
*/
public <T> T getServiceProvider(
final Class<T> category, final Filter filter, Hints hints, final Hints.Key key)
throws FactoryRegistryException {
synchronizeIteratorProviders();
final boolean debug = LOGGER.isLoggable(DEBUG_LEVEL);
if (debug) {
/*
* We are not required to insert the method name ("GetServiceProvider") in the
* message because it is part of the informations already stored by LogRecord,
* and formatted by the default java.util.logging.SimpleFormatter.
*
* Conventions for the message part according java.util.logging.Logger javadoc:
* - "ENTRY" at the begining of a method.
* - "RETURN" at the end of a method, if successful.
* - "THROW" in case of failure.
* - "CHECK" ... is our own addition to Sun's convention for this method ...
*/
debug("ENTRY", category, key, null, null);
}
Class<?> implementation = null;
if (key != null) {
/*
* Sanity check: make sure that the key class is appropriate for the category.
*/
final Class<?> valueClass = key.getValueClass();
if (!category.isAssignableFrom(valueClass)) {
if (debug) {
debug("THROW", category, key, "unexpected type:", valueClass);
}
throw new IllegalArgumentException(Errors.format(ErrorKeys.ILLEGAL_KEY_$1, key));
}
if (hints != null) {
final Object hint = hints.get(key);
if (hint != null) {
if (debug) {
debug("CHECK", category, key, "user provided a", hint.getClass());
}
if (category.isInstance(hint)) {
/*
* The factory implementation was given explicitly by the user.
* Nothing to do; we are done.
*/
if (debug) {
debug("RETURN", category, key, "return hint as provided.", null);
}
return category.cast(hint);
}
/*
* Before to pass the hints to the private 'getServiceImplementation' method,
* remove the hint for the user-supplied key. This is because this hint has
* been processed by this public 'getServiceProvider' method, and the policy
* is to remove the processed hints before to pass them to child dependencies
* (see the "Check recursively in factory dependencies" comment elswhere in
* this class).
*
* Use case: DefaultDataSourceTest invokes indirectly 'getServiceProvider'
* with a "CRS_AUTHORITY_FACTORY = ThreadedEpsgFactory.class" hint. However
* ThreadedEpsgFactory (in the org.geotools.referencing.factory.epsg package)
* is a wrapper around DirectEpsgFactory, and defines this dependency through
* a "CRS_AUTHORITY_FACTORY = DirectEpsgFactory.class" hint. There is no way
* to match this hint for both factories in same time. Since we must choose
* one, we assume that the user is interrested in the most top level one and
* discart this particular hint for the dependencies.
*/
hints = new Hints(hints);
if (hints.remove(key) != hint) {
// Should never happen except on concurrent modification in an other thread.
throw new AssertionError(key);
}
/*
* If the user accepts many implementation classes, then try all of them in
* the preference order given by the user. The last class (or the singleton
* if the hint was not an array) will be tried using the "normal" path
* (oustide the loop) in order to get the error message in case of failure.
*/
if (hint instanceof Class<?>[]) {
final Class<?>[] types = (Class<?>[]) hint;
final int length = types.length;
for (int i = 0; i < length - 1; i++) {
final Class<?> type = types[i];
if (debug) {
debug("CHECK", category, key, "consider hint[" + i + ']', type);
}
final T candidate = getServiceImplementation(category, type, filter, hints);
if (candidate != null) {
if (debug) {
debug("RETURN", category, key, "found implementation", candidate.getClass());
}
return candidate;
}
}
if (length != 0) {
implementation = types[length - 1]; // Last try to be done below.
}
} else {
implementation = (Class<?>) hint;
}
}
}
}
if (debug && implementation != null) {
debug("CHECK", category, key, "consider hint[last]", implementation);
}
final T candidate = getServiceImplementation(category, implementation, filter, hints);
if (candidate != null) {
if (debug) {
debug("RETURN", category, key, "found implementation", candidate.getClass());
}
return candidate;
}
if (debug) {
debug("THROW", category, key, "could not find implementation.", null);
}
throw new FactoryNotFoundException(
Errors.format(
ErrorKeys.FACTORY_NOT_FOUND_$1, implementation != null ? implementation : category));
}
