contrib/src/test/java/org/apache/apex/malhar/contrib/util/TupleGenerator.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.apex.malhar.contrib.util;

import java.lang.reflect.Constructor;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * This is a copy from contrib, should be merged later.
 *
 */
public class TupleGenerator<T>
{
  private static final Logger logger = LoggerFactory.getLogger( TupleGenerator.class );

  private volatile long rowId = 0;
  private Constructor<T> constructor;

  private static Class<?>[] paramTypes = new Class<?>[]{Long.class, long.class, Integer.class, int.class };

  public TupleGenerator()
  {
  }

  public TupleGenerator( Class<T> tupleClass )
  {
    useTupleClass( tupleClass );
  }

  public void useTupleClass( Class<T> tupleClass )
  {
    for ( Class<?> paramType : paramTypes ) {
      constructor = tryGetConstructor( tupleClass, paramType );
      if ( constructor != null ) {
        break;
      }
    }
    if ( constructor == null ) {
      logger.error( "Not found proper constructor." );
      throw new RuntimeException( "Not found proper constructor." );
    }
  }

  protected Constructor<T> tryGetConstructor( Class<T> tupleClass, Class<?> parameterType )
  {
    try {
      return tupleClass.getConstructor( parameterType );
    } catch ( Exception e ) {
      return null;
    }
  }

  public void reset()
  {
    rowId = 0;
  }

  public T getNextTuple()
  {
    if ( constructor == null ) {
      throw new RuntimeException( "Not found proper constructor." );
    }
    long curRowId = ++rowId;
    try {
      return constructor.newInstance( curRowId );
    } catch ( Exception e) {
      logger.error( "newInstance failed.", e );
      return null;
    }
  }

}