TypeCapture.java

/*
 * Copyright © 2015 Cask Data, Inc.
 *
 * 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 co.cask.cdap.etl.common.guice;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import static com.google.common.base.Preconditions.checkArgument;

/**
 * Captures the actual type of {@code T}.
 *
 * @author Ben Yu
 */
abstract class TypeCapture<T> {

  /** Returns the captured type. */
  final Type capture() {
    Type superclass = getClass().getGenericSuperclass();
    checkArgument(superclass instanceof ParameterizedType,
                  "%s isn't parameterized", superclass);
    return ((ParameterizedType) superclass).getActualTypeArguments()[0];
  }
}