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  package org.apache.cayenne.dba;
  
  import org.apache.cayenne.di.DIRuntimeException;
  
  import java.util.Map;
  import java.util.Objects;
  
  /**
   * An injectable provider that returns a given service in a context of a specific {@link DbAdapter}.
   * This allows modules to create adapter-specific extensions without altering DbAdapter API.
   *
   * @since 4.0
   */
  public class PerAdapterProvider<T> {
  
      private Map<String, T> perAdapterValues;
      private T defaultValue;
  
      public PerAdapterProvider(Map<String, T> perAdapterValues, T defaultValue) {
          this.perAdapterValues = Objects.requireNonNull(perAdapterValues);
          this.defaultValue = Objects.requireNonNull(defaultValue);
      }
  
      public T get(DbAdapter adapter) throws DIRuntimeException {
          T t = perAdapterValues.get(adapter.unwrap().getClass().getName());
          return t != null ? t : defaultValue;
      }
  }
  