Richard Zowalla created OPENNLP-1972:
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Summary: Add a generic provider SPI for service-loaded components
Key: OPENNLP-1972
URL: https://issues.apache.org/jira/browse/OPENNLP-1972
Project: OpenNLP
Issue Type: Improvement
Reporter: Richard Zowalla
Adds to {{opennlp.tools.util.ext}} in opennlp\-api:
\* {{Provider}}: {{name\(\)}}, {{priority\(\)}}, {{isAvailable\(\)}},
{{supports\(ProviderSpec\)}}, {{create\(ProviderSpec\)}}.
\* {{Providers>}}: created with {{of\(spi\)}}, {{of\(spi, loader\)}} or
{{of\(spi, loader, configuration\)}}; {{installed\(\)}}, {{byName\(name\)}},
{{supporting\(spec\)}}, {{select\(spec\)}}, {{configurationKey\(\)}},
{{disabledKey\(\)}}, {{allowedKey\(\)}}.
\* {{ProviderSpec}}: an optional URI location plus string options.
\* {{ProviderResolutionException}} with {{UnsatisfiedProviderException}} and
{{AmbiguousProviderException}}.
Each service interface gets its own SPI sub\-interface and service file, so a
lookup only instantiates providers of that service interface. {{select}}
considers the available providers that support the spec; {{opennlp.provider.}}
narrows them to one name, {{opennlp.provider..disabled}} vetoes names and
provider classes and {{opennlp.provider..allowed}} restricts which provider
classes may be instantiated at all; the highest priority wins and a tie is
ambiguous. The keys are read from {{META\-INF/opennlp/providers.properties}} of
the class loader used for the lookup, overridden by system properties, or from
a source the application passes.
A provider that fails to load, has an invalid name or throws from {{name\(\)}}
or {{priority\(\)}} is skipped while the providers are looked up; one that
throws from {{isAvailable\(\)}} or {{supports\(\)}} is left out of that
resolution. A class loader that cannot list or read its files fails the lookup
with {{ProviderResolutionException}}.
The implementation is thread\-safe, keeps no static state so that an
application server can undeploy an application, and uses no reflection, so a
native image needs no metadata for the lookup itself \(OPENNLP\-1954\).
{{DocumentAnnotatorProvider}} is the first service interface, with
{{StemmerAnnotatorProvider}} in opennlp\-runtime.
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