ReplacingClassLoader.java

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package io.grpc;

import java.io.IOException;
import java.net.URL;
import java.util.Enumeration;

/**
 * A ClassLoader to help test service providers.
 */
public class ReplacingClassLoader extends ClassLoader {
  private final String resource;
  private final String replacement;

  /**
   * Construct an instance where {@code replacement} is loaded instead of {@code resource}.
   */
  public ReplacingClassLoader(ClassLoader parent, String resource, String replacement) {
    super(parent);
    this.resource = resource;
    this.replacement = replacement;
  }

  @Override
  public URL getResource(String name) {
    if (resource.equals(name)) {
      return getParent().getResource(replacement);
    }
    return super.getResource(name);
  }

  @Override
  public Enumeration<URL> getResources(String name) throws IOException {
    if (resource.equals(name)) {
      return getParent().getResources(replacement);
    }
    return super.getResources(name);
  }
}