MongoDB系列教程（六）：java操作mongodb实例

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：

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) {