^_^[root@:/usr/local/mongodb/bin]#./mongo
MongoDB shell version: 1.8.2
connecting to: test
> var a = {name:"C++"}                                                                                           
> db 
test
> db.language.save(a)
> db.language.find()
{ "_id" : ObjectId("4da32c897d2de864e0448e06"), "name" : "C++" }
> var b = {name:"javascript"}
> db.language.save(b)
> db.language.find()
{ "_id" : ObjectId("4da32c897d2de864e0448e06"), "name" : "C++" }
{ "_id" : ObjectId("4da32cb17d2de864e0448e07"), "name" : "javascript" }
> lan = {name:"obj1",computer:[new DBRef('language',a._id)]}
{
        "name" : "obj1",
        "computer" : [
                {
                        "$ref" : "language",
                        "$id" : ObjectId("4da32c897d2de864e0448e06")
                }
        ]
}
> lan.computer[0]
{ "$ref" : "language", "$id" : ObjectId("4da32c897d2de864e0448e06") }
> lan.computer[0].fetch()
{ "_id" : ObjectId("4da32c897d2de864e0448e06"), "name" : "C++" }
> db.language.insert(lan)                                                                                        
> db.language.find()
{ "_id" : ObjectId("4da32c897d2de864e0448e06"), "name" : "C++" }
{ "_id" : ObjectId("4da32cb17d2de864e0448e07"), "name" : "javascript" }
{ "_id" : ObjectId("4da33b487d2de864e0448e08"), "name" : "obj1", "computer" : [ { "$ref" : "language", "$id" : ObjectId("4da32c897d2de864e0448e06") } ] }
> db.language.findOne({name:"obj1"}).computer[0].fetch()                                                         
{ "_id" : ObjectId("4da32c897d2de864e0448e06"), "name" : "C++" }
> lan2 = {name:"obj2",computer:[new DBRef('language',b._id)]}     
{
        "name" : "obj2",
        "computer" : [
                {
                        "$ref" : "language",
                        "$id" : ObjectId("4da32cb17d2de864e0448e07")
                }
        ]
}
> db.language.insert(lan2)
> db.language.find()
{ "_id" : ObjectId("4da32c897d2de864e0448e06"), "name" : "C++" }
{ "_id" : ObjectId("4da32cb17d2de864e0448e07"), "name" : "javascript" }
{ "_id" : ObjectId("4da33b487d2de864e0448e08"), "name" : "obj1", "computer" : [ { "$ref" : "language", "$id" : ObjectId("4da32c897d2de864e0448e06") } ] }