MongoDB（六）java操作mongodb增删改查

    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，就能够直接进入testMongoDb。由于用户能够进入系统的数据库。就是超级管理员，use testMongoDb后。为该数据库设置username和password，db.addUser('root','root')，这样我们在程序中连该数据库，并实现增删改查，代码例如以下所看到的。

    代码例如以下所看到的：

<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();
    }

  }
}

控制台输入结果例如以下：

    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