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package com.sun.grizzly;

import com.sun.grizzly.util.DataStructures;
import java.util.Queue;
import java.util.concurrent.Callable;

/**
 * This interface is responsible of handling {@link ConnectorHandler}
 * instance creation. This interface can be used to implement a connection
 * pooling mechanism.
 *
 * @param E ConnectorHandler implementation this pool will manage
 * @author Jeanfrancois
 */
public interface ConnectorInstanceHandler {
    
    
    /**
     * Acquire a {@link ConnectorHandler}
     * @return instance of ConnectorHandler
     */
    public E acquire();
    
    
    /**
     * Release a {@link ConnectorHandler}
     * @param connectorHandler release connector handler
     */
    public void release(E connectorHandler);
    
    /**
     * Concurrent Queue ConnectorInstanceHandler implementation
     * @param E ConnectorHandler implementation this pool will manage
     */
    public abstract class ConcurrentQueueConnectorInstanceHandler implements ConnectorInstanceHandler {
        /**
         * Simple queue used to pool {@link ConnectorHandler}
         */
        private final Queue pool;
        
        
        public ConcurrentQueueConnectorInstanceHandler(){
            pool = (Queue) DataStructures.getCLQinstance();
        }
        
        /**
         * Acquire a {@link ConnectorHandler}
         */
        public E acquire(){
            E connectorHandler = pool.poll();
            if (connectorHandler == null){
                connectorHandler = newInstance();
            }
            return connectorHandler;
        }
        
        /**
         * Release a {@link ConnectorHandler}
         */
        public void release(E connectorHandler){
            pool.offer(connectorHandler);
        }
        
        public abstract E newInstance();
    }
    
    /**
     * Concurrent Queue ConnectorInstanceHandler implementation
     * @param E ConnectorHandler implementation this pool will manage
     */
    public class ConcurrentQueueDelegateCIH 
            extends ConcurrentQueueConnectorInstanceHandler {
        
        // ConnectorHandler instance creator
        private final Callable delegate;
        
        public ConcurrentQueueDelegateCIH(Callable delegate) {
            this.delegate = delegate;
        }
        
        public E newInstance() {
            try {
                return delegate.call();
            } catch(Exception e) {
                throw new IllegalStateException("Unexpected exception", e);
            }
        }
    }
}