java操作mysql数据库的代码我们已经了如指掌了，增删改查，java对mongodb数据库也是类似的操作，先是数据库连接，再是进行操作。

    首先我们进入进入admin数据库，然后建立自己的数据库testMongoDb，进入admin数据库后，就可以直接进入testMongoDb，因为用户可以进入系统的数据库，就是超级管理员，use testMongoDb后，为该数据库设置用户名和密码，db.addUser(‘root‘,‘root‘)，这样我们在程序中连该数据库，并实现增删改查，代码如下所示。

    代码如下所示：

<pre name="code" class="java">package com.mkyong.core;

import java.net.UnknownHostException;
import java.util.Date;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.Mongo;
import com.mongodb.MongoException;

/**
 * Java + MongoDB Hello world Example
 * 
 */
public class App {
	public static void main(String[] args) {

		try {

			/**** Connect to MongoDB ****/
			// Since 2.10.0, uses MongoClient
			//MongoClient mongo = new MongoClient("localhost", 27017);
			
			Mongo mongo = new Mongo("127.0.0.1",27017);
			
          
			/**** Get database ****/
			// if database doesn't exists, MongoDB will create it for you
			DB db = mongo.getDB("testMongoDb");
			//database username  root  and password root 
			boolean ok = db.authenticate("root","root".toCharArray());
			if(ok){
				System.out.println("db connection success！");
				
			}{
				System.out.println("db connection fail ！");
			}
			/**** Get collection / table from 'testMongoDb' ****/
			// if collection doesn't exists, MongoDB will create it for you
			DBCollection table = db.getCollection("user");

			/**** Insert ****/
			// create a document to store key and value
			BasicDBObject document = new BasicDBObject();
			document.put("name", "mkyong");
			document.put("age", 30);
			document.put("createdDate", new Date());
			table.insert(document);

			/**** Find and display ****/
			BasicDBObject searchQuery = new BasicDBObject();
			searchQuery.put("name", "mkyong");

			DBCursor cursor = table.find(searchQuery);

			while (cursor.hasNext()) {
				System.out.println(cursor.next());
			}

			/**** Update ****/
			// search document where name="mkyong" and update it with new values
			BasicDBObject query = new BasicDBObject();
			query.put("name", "mkyong");

			BasicDBObject newDocument = new BasicDBObject();
			newDocument.put("name", "mkyong-updated");

			BasicDBObject updateObj = new BasicDBObject();
			updateObj.put("$set", newDocument);

			table.update(query, updateObj);

			/**** Find and display ****/
			BasicDBObject searchQuery2 
				= new BasicDBObject().append("name", "mkyong-updated");

			DBCursor cursor2 = table.find(searchQuery2);

			while (cursor2.hasNext()) {
				System.out.println(cursor2.next());
			}

			/**** Done ****/
			System.out.println("Done");

		} catch (UnknownHostException e) {
			e.printStackTrace();
		} catch (MongoException e) {
			e.printStackTrace();
		}

	}
}

    db connection success！
    db connection fail ！
{ "_id" : { "$oid" : "544073c4d58dfa6e469555ba"} , "name" : "mkyong" , "age" : 30 , "createdDate" : { "$date" : "2014-10-17T01:41:24.479Z"}}

{ "_id" : { "$oid" : "543e154bd58d704982fd38f0"} , "name" : "mkyong-updated" , "age" : 30 , "createdDate" : { "$date" : "2014-10-15T06:33:47.321Z"}}
{ "_id" : { "$oid" : "5440719dd58d08a207605c8e"} , "name" : "mkyong-updated" , "age" : 30 , "createdDate" : { "$date" : "2014-10-17T01:32:13.922Z"}}
{ "_id" : { "$oid" : "544073c4d58dfa6e469555ba"} , "name" : "mkyong-updated" , "age" : 30 , "createdDate" : { "$date" : "2014-10-17T01:41:24.479Z"}}
Done

源码下载：http://download.csdn.net/detail/lovesummerforever/8047875

深入浅出MongoDB（六）java操作mongodb增删改查