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    • io.appulse.utils.ReflectionUtils Maven / Gradle / Ivy

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    /*
 * Copyright 2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.appulse.utils;

import static java.util.Optional.empty;
import static java.util.Optional.ofNullable;

import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Optional;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Stream;

import lombok.NonNull;
import lombok.SneakyThrows;
import lombok.val;

/**
 * Different reflection helpers.
 *
 * @author Artem Labazin
 * @since 1.0.1
 */
public final class ReflectionUtils {

  /**
   * Extracts field value from object by its name.
   *
   * @param obj  object, from which need to extract field's value.
   * @param name field's name
   *
   * @return optional - field's value or nothing.
   */
  @SneakyThrows
  public static Optional getFieldValueFrom (@NonNull Object obj, @NonNull String name) {
    val optional = findIn(obj, Class::getDeclaredFields, field -> field.getName().equals(name));
    if (optional.isPresent()) {
      val field = optional.get();
      AccessController.doPrivileged(new PrivilegedAction() {

        @Override
        public Object run () {
          field.setAccessible(true);
          return null;
        }
      });
      val value = field.get(obj);
      return ofNullable(value);
    }
    return empty();
  }

  /**
   * Invoke method of object with specified arguments.
   *
   * @param obj     object
   * @param name    method's name
   * @param arguments optional arguments for method
   *
   * @return method's invocation result.
   */
  @SneakyThrows
  public static Object invokeMethodOf (@NonNull Object obj, @NonNull String name, Object... arguments) {
    val optional = findIn(obj, Class::getDeclaredMethods, method -> method.getName().equals(name));
    if (optional.isPresent()) {
      val method = optional.get();
      return method.invoke(obj, arguments);
    }
    return null;
  }

  // Searches method/field in object by predicate.
  private static  Optional findIn (Object obj, Function, T[]> extractor, Predicate predicate) {
    Class current = obj.getClass();

    while (current != null) {
      val values = extractor.apply(current);
      val optional = Stream.of(values)
          .filter(predicate)
          .findFirst();

      if (optional.isPresent()) {
        return optional;
      }
      current = current.getSuperclass();
    }
    return empty();
  }

  private ReflectionUtils () {
  }
}
    
    
    
    

    




    
    
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