internal.sdmxdl.web.spi.RegistryLoader Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of sdmx-dl-api Show documentation

Easily download official statistics - API

The newest version!

package internal.sdmxdl.web.spi;

import java.lang.Iterable;
import java.util.Collections;
import java.util.Comparator;
import java.util.ServiceLoader;
import java.util.function.Predicate;
import java.util.regex.Pattern;
import java.util.stream.StreamSupport;
import sdmxdl.web.spi.Registry;

/**
 * Custom service loader for {@link sdmxdl.web.spi.Registry}.
 * 
This class is thread-safe.
 * Properties:
 * 

 * Quantifier: SINGLE
 * Fallback: {@link internal.sdmxdl.web.spi.NoOpRegistry}
 * Preprocessing: wrapper: none filters:[] sorters:[getRegistryRank]
 * Mutability: NONE
 * Singleton: false
 * Name: internal.{{canonicalName}}Loader
 * Backend: null
 * Cleaner: null
 * Batch: false
 * Batch name: null
 * 
 */
public final class RegistryLoader {
  public static final Pattern ID_PATTERN = Pattern.compile("^[A-Z0-9]+(?:_[A-Z0-9]+)*$");

  private final Iterable source = ServiceLoader.load(Registry.class);

  private final Predicate filter = o -> ID_PATTERN.matcher(o.getRegistryId()).matches();

  private final Comparator sorter = Collections.reverseOrder(Comparator.comparingInt(Registry::getRegistryRank));

  private final Registry resource = doLoad();

  private Registry doLoad() {
    return StreamSupport.stream(source.spliterator(), false)
        .filter(filter)
        .sorted(sorter)
        .findFirst()
        .orElseGet(() -> NoOpRegistry.INSTANCE);
  }

  /**
   * Gets a {@link sdmxdl.web.spi.Registry} instance.
   * 
This method is thread-safe.
   * @return the current non-null value
   */
  public Registry get() {
    return resource;
  }

  /**
   * Gets a {@link sdmxdl.web.spi.Registry} instance.
   * 
This is equivalent to the following code: new RegistryLoader().get()
   * 
Therefore, the returned value might be different at each call.
   * 
This method is thread-safe.
   * @return a non-null value
   */
  public static Registry load() {
    return new RegistryLoader().get();
  }
}