org.openqa.selenium.grid.config.AnnotatedConfig Maven / Gradle / Ivy

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package org.openqa.selenium.grid.config;

import com.google.common.collect.ImmutableMap;

import java.lang.reflect.Field;
import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.Collection;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;

/**
 * A form of {@link Config} that is generated by looking at fields in the constructor arg that are
 * annotated with {@link ConfigValue}. The class hierarchy is walked from closest to Object to the
 * constructor argument's type, null values are ignored, and the order in which fields are read is
 * not stable (meaning duplicate config values may give different values each time).
 * 
 * The main use of this class is to allow an object configured using (for example) jcommander to be
 * used directly within the app, without requiring intermediate support classes to convert flags to
 * config values.
 */
public class AnnotatedConfig implements Config {

  private final Map> config;

  public AnnotatedConfig(Object obj) {
    Map> values = new HashMap<>();

    Deque allConfigValues = findConfigFields(obj.getClass());

    for (Field field : allConfigValues) {
      if (Collection.class.isAssignableFrom(field.getType())) {
        throw new ConfigException("Collection fields may not be used for configuration: " + field);
      }

      if (Map.class.isAssignableFrom(field.getType())) {
        throw new ConfigException("Map fields may not be used for configuration: " + field);
      }

      field.setAccessible(true);
      Object value;
      try {
        value = field.get(obj);
      } catch (IllegalAccessException e) {
        throw new ConfigException("Unable to read field: " + field);
      }

      if (value == null) {
        continue;
      }

      ConfigValue annotation = field.getAnnotation(ConfigValue.class);
      Map section = values.getOrDefault(annotation.section(), new HashMap<>());
      section.put(annotation.name(), String.valueOf(value));
      values.put(annotation.section(), section);
    }

    config = ImmutableMap.copyOf(values);
  }

  private Deque findConfigFields(Class clazz) {
    Deque toSet = new ArrayDeque<>();
    Set> toVisit = new HashSet<>();
    toVisit.add(clazz);

    Set> seen = new HashSet<>();

    while (!toVisit.isEmpty()) {
      clazz = toVisit.iterator().next();
      toVisit.remove(clazz);
      seen.add(clazz);

      Arrays.stream(clazz.getDeclaredFields())
          .filter(field -> field.getAnnotation(ConfigValue.class) != null)
          .forEach(toSet::addFirst);

      Class toAdd = clazz.getSuperclass();
      if (!Object.class.equals(toAdd) && !seen.contains(toAdd)) {
        toVisit.add(toAdd);
      }
      Arrays.stream(clazz.getInterfaces())
          .filter(face -> !seen.contains(face))
          .forEach(toVisit::add);
    }

    return toSet;
  }

  @Override
  public Optional get(String section, String option) {
    Objects.requireNonNull(section, "Section name not set");
    Objects.requireNonNull(option, "Option name not set");

    Map sec = config.get(section);
    if (sec == null) {
      return Optional.empty();
    }

    return Optional.ofNullable(sec.get(option));
  }
}