src/test/java/org/apache/datasketches/quantilescommon/ReflectUtilityTest.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.datasketches.quantilescommon;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import static org.apache.datasketches.quantilescommon.QuantileSearchCriteria.*;
import static org.testng.Assert.assertEquals;

import org.apache.datasketches.req.ReqSketchSortedView;
import org.testng.annotations.Test;

public final class ReflectUtilityTest {

  private ReflectUtilityTest() {}

  static final Class<?> REQ_SV;
  static final Class<?> KLL_FLOATS_SV;
  static final Class<?> DOUBLES_SV;

  static final Constructor<?> REQ_SV_CTOR;
  static final Constructor<?> KLL_FLOATS_SV_CTOR;
  static final Constructor<?> DOUBLES_SV_CTOR;

  static {
    REQ_SV = getClass("org.apache.datasketches.req.ReqSketchSortedView");
    KLL_FLOATS_SV = getClass("org.apache.datasketches.quantilescommon.FloatsSketchSortedView");
    DOUBLES_SV = getClass("org.apache.datasketches.quantilescommon.DoublesSketchSortedView");

    REQ_SV_CTOR =
        getConstructor(REQ_SV, float[].class, long[].class, long.class, float.class, float.class);
    KLL_FLOATS_SV_CTOR =
        getConstructor(KLL_FLOATS_SV, float[].class, long[].class, long.class, float.class, float.class);
    DOUBLES_SV_CTOR =
        getConstructor(DOUBLES_SV, double[].class, long[].class, long.class, double.class, double.class);
  }

  @Test //Example
  public static void checkCtr() throws Exception {
    float[] farr = { 10, 20, 30 };
    long[] larr = { 1, 2, 3 };
    long n = 3;
    ReqSketchSortedView reqSV =
        (ReqSketchSortedView) REQ_SV_CTOR.newInstance(farr, larr, n, 10f, 30f);
    float q = reqSV.getQuantile(1.0, INCLUSIVE);
    assertEquals(q, 30f);
  }

  /**
   * Gets a Class reference to the given class loaded by the SystemClassLoader.
   * This will work for private, package-private and abstract classes.
   * @param fullyQualifiedBinaryName the binary name is the name of the class file on disk. This does not instantiate
   * a concrete class, but allows access to constructors, static fields and static methods.
   * @return the Class object of the given class.
   */
  public static Class<?> getClass(final String fullyQualifiedBinaryName) {
    try {
      final ClassLoader scl = ClassLoader.getSystemClassLoader();
      return scl.loadClass(fullyQualifiedBinaryName);
    } catch (final ClassNotFoundException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Gets a declared constructor given the owner class and parameter types
   * @param ownerClass the Class object of the class loaded by the SystemClassLoader.
   * @param parameterTypes parameter types for the constructor
   * @return the constructor
   */
  public static Constructor<?> getConstructor(final Class<?> ownerClass, final Class<?>... parameterTypes ) {
    try {
      final Constructor<?> ctor = ownerClass.getDeclaredConstructor(parameterTypes);
      ctor.setAccessible(true);
      return ctor;
    } catch (final NoSuchMethodException | SecurityException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Gets a class instance from its constructor and initializing arguments.
   * @param constructor the given Constructor
   * @param initargs the initializing arguments
   * @return the instantiated class.
   */
  public static Object getInstance(final Constructor<?> constructor, final Object... initargs) {
    try {
      constructor.setAccessible(true);
      return constructor.newInstance(initargs);
    } catch (final InstantiationException | IllegalAccessException | IllegalArgumentException
          | InvocationTargetException | SecurityException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Gets a declared field of the given the loaded owner class and field name. The accessible flag will be set true.
   * @param ownerClass the Class object of the class loaded by the SystemClassLoader.
   * @param fieldName the desired field name
   * @return the desired field.
   */
  public static Field getField(final Class<?> ownerClass, final String fieldName) {
    try {
      final Field field = ownerClass.getDeclaredField(fieldName);
      field.setAccessible(true);
      return field;
    } catch (final NoSuchFieldException | SecurityException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Gets a field value given the loaded owner class and the Field. The accessible flag will be set true.
   * @param ownerClass the loaded class owning the field
   * @param field The Field object
   * @return the returned value as an object.
   */
  public static Object getFieldValue(final Class<?> ownerClass, final Field field) {
    try {
      field.setAccessible(true);
      return field.get(ownerClass);
    } catch (final IllegalAccessException | SecurityException | IllegalArgumentException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Gets a declared method of the given the loaded owning class, method name and parameter types.
   * The accessible flag will be set true.
   * @param ownerClass the given
   * @param methodName the given method name
   * @param parameterTypes the list of parameter types
   * @return the desired method.
   */
  public static Method getMethod(
      final Class<?> ownerClass, final String methodName, final Class<?>... parameterTypes ) {
    try {
      final Method method = (parameterTypes == null)
          ? ownerClass.getDeclaredMethod(methodName)
          : ownerClass.getDeclaredMethod(methodName, parameterTypes);
      method.setAccessible(true);
      return method;
    } catch (final NoSuchMethodException | SecurityException e) {
      throw new RuntimeException(e);
    }
  }

}