How to update embedded document in mongo?

Question

I am having the following document in the mongo db.

  { "_id" : ObjectId("50656f33a4e82d3f98291eff"), 
     "description" : "gdfgdfgdfg",
     "menus" : [    
               {    
                 "name" : "gdfgdfgdfg",     
                  "description" : "dfgdgd",     
                  "text" : "dfgdfg",    
                  "key" : "2",  
                  "onSelect" : "yyy",   
                  "_id" : ObjectId("50656f3ca4e82d3f98291f00") 
              }, 
               {    
                 "name" : "rtytry",     
                  "description" : "gffhf",  
                  "text" : "dfgdfg",    
                  "key" : "2",  
                  "onSelect" : "yyy",   
                  "_id" : ObjectId("50656f3ca4e82d3f98281f00") 
              }],
      "select":"ffdfgd"
   }

I want to do automatic update of menus {
"name" : "gdfgdfgdfg",
"description" : "dfgdgd",
"text" : "dfgdfg",
"key" : "2",
"onSelect" : "yyy",
"_id" : ObjectId("50656f3ca4e82d3f98291f00") }

I have tried using the following code:

         BasicDBObject query = new BasicDBObject("_id", new ObjectId("50656f33a4e82d3f98291eff"));

         BasicDBObject update = new BasicDBObject("_id", ObjectId("50656f3ca4e82d3f98291f00"));

         BasicDBObject updateCommand = new BasicDBObject("$set", new BasicDBObject("menus", update));

         collection.update(query, updateCommand);

The result i got is

  { "_id" : ObjectId("50656f33a4e82d3f98291eff"), 
 "description" : "gdfgdfgdfg",
 "menus" :    
           {    
             "name" : "gdfgdfgdfg",     
              "description" : "dfgdgd",     
              "text" : "dfgdfg",    
              "key" : "2",  
              "onSelect" : "yyy",   
              "_id" : ObjectId("50656f3ca4e82d3f98291f00") 
          },
  "select":"ffdfgd"

}

but i want to update in the same embedded document.

Any one guide me ....Thanks in advance

Answer 1

Ok After having to read this a couple of times (English...) I think I understand now.

You want to upto the subdocument with the _id 50656f3ca4e82d3f98291f00 with:

{
"name" : "gdfgdfgdfg",
"description" : "dfgdgd",
"text" : "dfgdfg",
"key" : "2",
"onSelect" : "yyy",
"_id" : ObjectId("50656f3ca4e82d3f98291f00") 
} 

First problem you have is that your code merely sets menus field to this object. What you need is the postional operator. So you need to do a dot notation find (warning my Java is a little rusty):

query.append("menus._id", new ObjectId("50656f3ca4e82d3f98291f00"));

And then use that positional operator to update in position:

BasicDBObject update_document = new BasicDBObject("menus.$.name", my_new_subdocument.name);
update_document.append("menus.$.description", my_new_subdocument.description);
// All the other fields

BasicDBObject updateCommand = new BasicDBObject("$set", update_document);

Hopefully that should do the trick.