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package org.objenesis;

import java.util.HashMap;
import java.util.Map;
import java.util.WeakHashMap;

import org.objenesis.instantiator.ObjectInstantiator;
import org.objenesis.strategy.InstantiatorStrategy;

/**
 * Base class to extend if you want to have a class providing your own default strategy. Can also be
 * instantiated directly.
 * 
 * @author Henri Tremblay
 */
public class ObjenesisBase implements Objenesis {

   /** Strategy used by this Objenesi implementation to create classes */
   protected final InstantiatorStrategy strategy;

   /** Strategy cache. Key = Class, Value = InstantiatorStrategy */
   protected Map cache;

   /**
    * Constructor allowing to pick a strategy and using cache
    * 
    * @param strategy Strategy to use
    */
   public ObjenesisBase(InstantiatorStrategy strategy) {
      this(strategy, true);
   }

   /**
    * Flexible constructor allowing to pick the strategy and if caching should be used
    * 
    * @param strategy Strategy to use
    * @param useCache If {@link ObjectInstantiator}s should be cached
    */
   public ObjenesisBase(InstantiatorStrategy strategy, boolean useCache) {
      if(strategy == null) {
         throw new IllegalArgumentException("A strategy can't be null");
      }
      this.strategy = strategy;
      this.cache = useCache ? new HashMap() : null;
   }

   public String toString() {
      return getClass().getName() + " using " + strategy.getClass().getName()
         + (cache == null ? " without" : " with") + " caching";
   }

   /**
    * Will create a new object without any constructor being called
    * 
    * @param clazz Class to instantiate
    * @return New instance of clazz
    */
   public Object newInstance(Class clazz) {
      return getInstantiatorOf(clazz).newInstance();
   }

   /**
    * Will pick the best instantiator for the provided class. If you need to create a lot of
    * instances from the same class, it is way more efficient to create them from the same
    * ObjectInstantiator than calling {@link #newInstance(Class)}.
    * 
    * @param clazz Class to instantiate
    * @return Instantiator dedicated to the class
    */
   public synchronized ObjectInstantiator getInstantiatorOf(Class clazz) {
      if(cache == null) {
         return strategy.newInstantiatorOf(clazz);
      }
      ObjectInstantiator instantiator = (ObjectInstantiator) cache.get(clazz.getName());
      if(instantiator == null) {
         instantiator = strategy.newInstantiatorOf(clazz);
         cache.put(clazz.getName(), instantiator);
      }
      return instantiator;
   }

}