ShardSelectImpl.java

/*
 * @(#)ShardSelectImpl.java 2012-8-1 下午10:00:00
 *
 * Copyright (c) 2011-2012 Makersoft.org all rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 *
 */
package org.makersoft.shards.select.impl;

import java.util.List;
import java.util.Map;

import org.apache.ibatis.session.SqlSession;
import org.makersoft.shards.Shard;
import org.makersoft.shards.ShardId;
import org.makersoft.shards.ShardOperation;
import org.makersoft.shards.select.SelectFactory;
import org.makersoft.shards.select.ShardSelect;
import org.makersoft.shards.strategy.access.ShardAccessStrategy;
import org.makersoft.shards.strategy.exit.impl.ConcatenateListsExitStrategy;
import org.makersoft.shards.strategy.exit.impl.ExitOperationsSelectCollector;
import org.makersoft.shards.strategy.exit.impl.SelectOneExitStrategy;
import org.makersoft.shards.strategy.reduce.ShardReduceStrategy;
import org.makersoft.shards.utils.ParameterUtil;

/**
 * 
 */
public class ShardSelectImpl implements ShardSelect {

	private final List<Shard> shards;

	private final SelectFactory selectFactory;
	
	private final ShardAccessStrategy shardAccessStrategy;
	
	/**
	 * The queryCollector is not used in ShardedQueryImpl as it would require
	 * this implementation to parse the query string and extract which exit
	 * operations would be appropriate. This member is a place holder for future
	 * development.
	 */
	private final ExitOperationsSelectCollector selectCollector;

	public ShardSelectImpl(List<Shard> shards, SelectFactory selectFactory,
			ShardAccessStrategy shardAccessStrategy, ShardReduceStrategy shardReduceStrategy) {
		this.shards = shards;
		this.selectFactory = selectFactory;
		this.shardAccessStrategy = shardAccessStrategy;
		this.selectCollector = new ExitOperationsSelectCollector(selectFactory, shardReduceStrategy);
	}

	@Override
	@SuppressWarnings("unchecked")
	public <E> List<E> getResultList() {
		ShardOperation<List<Object>> shardOp = new ShardOperation<List<Object>>() {
			public List<Object> execute(SqlSession session, ShardId shardId) {

				return session.selectList(selectFactory.getStatement(),
						ParameterUtil.resolve(selectFactory.getParameter(), shardId), 
						selectFactory.getRowBounds());
			}

			public String getOperationName() {
				return "getResultList()";
			}
		};

		return (List<E>) shardAccessStrategy.apply(shards, shardOp,
				new ConcatenateListsExitStrategy(), selectCollector);
	}

	@Override
	public <K, V> Map<K, V> getResultMap() {
//		ShardOperation<Map<K, V>> shardOp = new ShardOperation<Map<K, V>>() {
//			public Map<K, V> execute(SqlSession session, ShardId shardId) {
//
//				return session.selectMap(selectFactory.getStatement(), 
//						ParameterUtil.resolve(selectFactory.getParameter(), shardId), 
//						selectFactory.getMapKey());
//			}
//
//			public String getOperationName() {
//				return "getResultMap()";
//			}
//		};
		
		throw new UnsupportedOperationException();
		
//		return (T) shardAccessStrategy.apply(
//				shards,
//				shardOp,
//				new SelectOneExitStrategy(),
//				new ExitOperationsSelectMapCollector(selectFactory
//						.getStatement()));
	}

	@Override
	@SuppressWarnings("unchecked")
	public <T> T getSingleResult() {

		ShardOperation<Object> shardOp = new ShardOperation<Object>() {
			public Object execute(SqlSession session, ShardId shardId) {
				
				return session.selectOne(selectFactory.getStatement(),
						ParameterUtil.resolve(selectFactory.getParameter(), shardId));
			}

			public String getOperationName() {
				return "getSingleResult()";
			}
		};

		return (T) shardAccessStrategy.apply(
				shards,
				shardOp,
				new SelectOneExitStrategy(), selectCollector);
	}

}