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。
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： 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}}
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