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：

复制代码 代码如下:
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();
}

}
}

控制台输入结果如下：
复制代码 代码如下:
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://xiazai.jb51.net/201503/other/mongodb_helloworld.zip