Mongo java 基础 1

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本文介绍了一个简单的MongoDB Java客户端示例，展示了如何通过Java进行数据库连接、集合操作、文档写入及查询等基本功能。


package org.test;




import java.net.UnknownHostException;

import java.util.Iterator;




import com.mongodb.BasicDBObject;

import com.mongodb.DB;

import com.mongodb.DBCollection;

import com.mongodb.DBCursor;

import com.mongodb.DBObject;

import com.mongodb.MongoClient;

import com.mongodb.WriteConcern;




public class MongoInstance

{

MongoClient mongoClient = null;


public MongoInstance() throws UnknownHostException

{

// TODO Auto-generated constructor stub

this.mongoClient = new MongoClient();

}



public void test()

{

DB db = mongoClient.getDB("test");

//query all the collections in the db

Iterator it = db.getCollectionNames().iterator();

while(it.hasNext())

{

System.out.println(it.next());

}


// get a collection

DBCollection dbc = db.getCollection("things");

//setting write concern

dbc.setWriteConcern(WriteConcern.JOURNALED);


/* write a document

{

   "name" : "MongoDB",

   "type" : "database",

   "count" : 1,

   "info" : {

               x : 203,

               y : 102

             }

}

*/

BasicDBObject doc =  new BasicDBObject("_id",1).append("name","MongonDB").append("type", "database").append("count", 1).append("info", new BasicDBObject("x",203).append("y",111));

dbc.save(doc);


DBObject mydoc = dbc.findOne();

System.out.println(mydoc);


System.out.println("--------batch insert--------");

// insert batch

for(int i = 1 ;i < 3;i++)

dbc.insert(new BasicDBObject("i",i));


// get the size of a collection

System.out.println(dbc.getCount());


System.out.println("--------use cursor--------");

// use cursor

DBCursor cur = dbc.find();

while(cur != null && cur.hasNext())

{

System.out.println(cur.next());

}


System.out.println("--------query--------");

//query

BasicDBObject query = new BasicDBObject("i",new BasicDBObject("$gt",0));


cur = dbc.find(query);

while(cur != null && cur.hasNext())

{

System.out.println(cur.next());

}


dbc.remove(query);

}

public static void main(String[] args) throws UnknownHostException

{

MongoInstance mongon = new MongoInstance();

mongon.test();

}

}

需要到 mongo 官网上下载 mongo java-driver

this.mongoClient = new MongoClient();

只需要一个 mongoClient 实例即可，他是一个连接池。

MongoClient instance actually represents a pool of connections to the database; you will only need one instance of class MongoClient even with multiple threads