Class ServiceFactoryFactory (2.0.0)

This class is not intended for end users.

Provide factory instances for AppEngine APIs. Each API will have an associated FactoryProvider registered with this class. N.B. Once <xref uid="com.google.appengine.spi.ServiceFactoryFactory.

To construct the runtime mapping, this class first uses java.util.ServiceLoader to find all registered FactoryProvider entities using the ClassLoader of ServiceFactoryFactory. Finally, the explicitly registered providers <xref uid="com.google.appengine.spi.ServiceFactoryFactory.register(com.google.appengine.spi.FactoryProvider<I>)" data-throw-if-not-resolved="false">#register(FactoryProvider) are merged in.

If ServiceLoader locates multiple providers for a given factory interface, the ambiguity can be resolved by using the ServiceProvider#precedence annotation property (higher precedence wins; the google implementations all have precedence Integer.MIN_VALUE). An exception is raised if the ambiguity cannot be resolved. Note that explicit registration (<xref uid="com.google.appengine.spi.ServiceFactoryFactory.register(com.google.appengine.spi.FactoryProvider<I>)" data-throw-if-not-resolved="false">#register(FactoryProvider)) always takes precedence (it does not honor the ServiceProvider#precedence annotation property).

If this system property is set to "true" the thread context classloader is used (if non-null) when looking up API service implementations. Otherwise the class loader of this class is used.

Explicitly register a provider. This does not take the precedence (see FactoryProvider#getPrecedence()) of the provider into consideration; subsequent registrations will always override previous ones.

Used by AppEngine service factories. Returns an instance of the factory implementing the interface provide by base. Since there must always be a provider registered for a given base, an error will be raised if no appropriate registration is found.