Mongodb連接方法學習

項目中需要用到mongodb，據介紹mongodb的連接採用連接池的思路，可以僅保持一個實例，

參考http://blog.csdn.net/sheismylife/article/details/7090526的代碼完成自己的mongodb連接池控制類。

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實例
	private Mongo mongo;
	
	//採用單例模式
	private MongoDBUtil(){}
	
	private static class InnerHolder{
		static final MongoDBUtil INSTANCE = new MongoDBUtil();
	}
	
	public static MongoDBUtil getInstance(){
		return InnerHolder.INSTANCE;
	}
	
	/**
	 * 初始化Mongodb連接
	 * @throws UnknownHostException
	 * @throws MongoException
	 */
	public void init() throws UnknownHostException, MongoException{
		int poolSize = ConfigUtil.getInstance().getPoolSize(); //從配置文件中讀取連接個數
		
		if(poolSize == -1){
			poolSize = 10000;
		}
		
		System.setProperty("MONGO.POOLSIZE", String.valueOf(poolSize));
		
		if(this.mongo == null){
			//System.out.println("1st init Mongo instance"); //mongo實例僅實例化一次
			
			//從配置文件中讀取服務器地址及端口號
			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;
		}
	}
	
	/**
	 * 獲取DB實例
	 * @param dbName
	 * @return
	 */
	public DB getDB(String dbName){
		if(dbName != null && !dbName.equals("")){
			return this.mongo.getDB(dbName);
		}else{
			return null;
		}
	}
	
	/**
	 * 關閉Mongodb
	 */
	public void close(){
		if(this.mongo != null){
			this.mongo.close();
			this.mongo = null;
		}
	}
}