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The core Konfig module

There is a newer version: 0.0.3

package io.dropwizard.configuration;

import static java.util.Objects.requireNonNull;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;

import org.apache.commons.lang3.text.StrSubstitutor;

/**
 * A delegating {@link ConfigurationSourceProvider} which replaces variables in the underlying configuration
 * source according to the rules of a custom {@link org.apache.commons.lang3.text.StrSubstitutor}.
 */
public class SubstitutingSourceProvider implements ConfigurationSourceProvider {

  private final ConfigurationSourceProvider delegate;
  private final StrSubstitutor substitutor;

  /**
   * Create a new instance.
   *
   * @param delegate The underlying {@link io.dropwizard.configuration.ConfigurationSourceProvider}.
   * @param substitutor The custom {@link org.apache.commons.lang3.text.StrSubstitutor} implementation.
   */
  public SubstitutingSourceProvider(ConfigurationSourceProvider delegate, StrSubstitutor substitutor) {

    this.delegate = requireNonNull(delegate);
    this.substitutor = requireNonNull(substitutor);
  }

  @Override
  public InputStream open(String path) throws IOException {

    try (final InputStream in = delegate.open(path)) {

      final String config = convertStreamToString(in);

      final String substituted = substitutor.replace(config);

      return new ByteArrayInputStream(substituted.getBytes(StandardCharsets.UTF_8));
    }
  }

  private String convertStreamToString(java.io.InputStream is) {
    java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
    return s.hasNext() ? s.next() : "";
  }

}