Mongodb连接方法学习

项目中需要用到mongodb，据介绍mongodb的连接采用连接池的思路，可以仅保持一个实例，

参考http://blog.csdn.net/sheismylife/article/details/7090526的代码完成自己的mongodb连接池控制类。

package cn.cnic.jingshao.mongodbapp.util;

import java.net.UnknownHostException;

import com.mongodb.DB;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
import com.mongodb.MongoOptions;

public class MongoDBUtil {
	//唯一的Mongo实例
	private Mongo mongo;
	
	//采用单例模式
	private MongoDBUtil(){}
	
	private static class InnerHolder{
		static final MongoDBUtil INSTANCE = new MongoDBUtil();
	}
	
	public static MongoDBUtil getInstance(){
		return InnerHolder.INSTANCE;
	}
	
	/**
	 * 初始化Mongodb连接
	 * @throws UnknownHostException
	 * @throws MongoException
	 */
	public void init() throws UnknownHostException, MongoException{
		int poolSize = ConfigUtil.getInstance().getPoolSize(); //从配置文件中读取连接个数
		
		if(poolSize == -1){
			poolSize = 10000;
		}
		
		System.setProperty("MONGO.POOLSIZE", String.valueOf(poolSize));
		
		if(this.mongo == null){
			//System.out.println("1st init Mongo instance"); //mongo实例仅实例化一次
			
			//从配置文件中读取服务器地址及端口号
			String serverIp = ConfigUtil.getInstance().getServerIP();
			int portNum = ConfigUtil.getInstance().getPortNum();
			
			mongo = new Mongo(serverIp, portNum);
			MongoOptions options = mongo.getMongoOptions();
			options.autoConnectRetry = true;
			options.connectionsPerHost = poolSize;
		}
	}
	
	/**
	 * 获取DB实例
	 * @param dbName
	 * @return
	 */
	public DB getDB(String dbName){
		if(dbName != null && !dbName.equals("")){
			return this.mongo.getDB(dbName);
		}else{
			return null;
		}
	}
	
	/**
	 * 关闭Mongodb
	 */
	public void close(){
		if(this.mongo != null){
			this.mongo.close();
			this.mongo = null;
		}
	}
}