Accessing Array values in mongoDB with Java?

[MaRaVaN]

I am using Java Driver for mongoDB. I have a document which contains,
AlbumName, PreviewSize, ThumbSize, _id & Comments. PreviewSize &
ThumbSize are array. I want to know how can i query this document and
get any specific array value.

To be more clear, my document is like this,

Document : { "AlbumName" : "Test" , "PreviewSize" : [
{ "ImageName" : "tom_and_jerry_guns.jpg" , "BinaryImage" : <Binary
Data>} ,
{ "ImageName" : "Tom_and_Jerry,_Cartoons.jpg" , "BinaryImage" :
<Binary Data>} ,
{ "ImageName" : "TomJerry2_468x342.jpg" , "BinaryImage" : <Binary
Data>} ,
{ "ImageName" : "tom_and_jerry-5405.jpg" , "BinaryImage" : <Binary
Data>}] ,

"ThumbSize" : [ { "ImageName" : "tom_and_jerry_guns.jpg" ,
"BinaryImage" : <Binary Data>} ,
{ "ImageName" : "Tom_and_Jerry,_Cartoons.jpg" , "BinaryImage" :
<Binary Data>} ,
{ "ImageName" : "TomJerry2_468x342.jpg" , "BinaryImage" : <Binary
Data>} ,
{ "ImageName" : "tom_and_jerry-5405.jpg" , "BinaryImage" : <Binary
Data>}] ,

"_id" : { "$oid" : "4cef03b44613b5ba2d51a7b8"} , "comments" : [ ]}
How shall i get the TomJerry2_468x342.jpg and its <Binary Data> from
PreviewSize.

I am new to mongoDB. I dont know whether its possible or not. I just
constructed this document and i am able to update this document with
new images. I learnt this from this presentation.

My questions are how can i able to get the all the array contents at
once
and how can i able to get any specific <Binary Data> when i have its
name?

Any Suggestions would be more appreciative!

Thanks!!!

[Eliot Horowitz]

Do you mean you want the server to only return a certain value?
If so you can use the $slice operator.

Otherwise not sure what you mean.

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[MaRaVaN]

Thanks for your response!!!

I just showed up a single document with 2 array lists.

Is there any way to get them all with one query?

For example: // The code i tried,

BasicDBObject query = new BasicDBObject();
BasicDBObject field = new BasicDBObject();

field.put("PreviewSize", 1);

DBCursor cursor = coll.find(query, field);

while(cursor.hasNext()){
BasicDBObject result = (BasicDBObject) cursor.next();
int i = result.size();
String imageName = (String) ((BasicDBList)
result.get("PreviewSize")).get("ImageName");
System.out.println("Result Size: "+i+" Image Name :"+imageName);
byte[] imageByte = (byte[]) ((BasicDBList)
result.get("PreviewSize")).get("BinaryImage");
if(imageByte != null){System.out.println("Wow! Great!!! Its
Coming!!!");}
else{System.out.println("Try Another Way!");}
}// I am not sure this is exist(I am new to mongoDB). I need
something like that.
/* Some thing like the above list contains All contents of the
"PreviewSize" data <ImageName> & <BinaryData>.*/

I tried the above one, and the error message i got in the comsole is,

"Exception in thread "main" java.lang.IllegalArgumentException:
BasicBSONList can only work with numeric keys, not: [ImageName]"

I am totally new to mongoDB, like 3 days old :( .... Give me a way
out!!!!

And, i also want to know is there any way to retrieve specific data,
Like, if i know the "ImageName" can i get its BinaryData??

[MaRaVaN]

I tried to print the "result" Object and its size.

That is,

Result Size: 2
{ "PreviewSize" : [ { "ImageName" : "tom_and_jerry_guns.jpg" ,

"BinaryImage" : <Binary Data>} ,

{ "ImageName" : "Tom_and_Jerry,_Cartoons.jpg" , "BinaryImage" :
<Binary Data>} ,

{ "ImageName" : "TomJerry2_468x342.jpg" , "BinaryImage" : <Binary
Data>} ,

{ "ImageName" : "tom_and_jerry-5405.jpg" , "BinaryImage" : <Binary
Data>}] ,

"_id" : { "$oid" : "4cef03b44613b5ba2d51a7b8"}}

You can compare it with the actual document posted in first mail.
Almost i can see what i wanted,
But i think i am doing wrong with its receiver. What type of receiver
should i use???!!!!

Thanks!

"Exception in thread "main" java.lang.IllegalArgumentException:
BasicBSONList can only work with numeric keys, not: [ImageName]"

[Eliot Horowitz]

You have to iterate the List and find the object you want.
If you want to access it via name, you can change the schema from use
an array to a sub-document.

[MaRaVaN]

Thanks, that works...

But i am getting all images at once. Its not a problem when i need all
of them at once.

But, if need to show only one image means, i have to iterate through
all of the elements explicitly, like

if(cursor.hasNext())
{

BasicDBObject result = (BasicDBObject) cursor.next();

previewImageData = (BasicDBList) result.get("PreviewSize");
}
for(int i = 0; i<previewImageData.size(); i++)
{
String searchImage = (String) ((BSONObject)
previewImageData.get(i)).get("ImageName");
if(searchImage.equals(imageName))
{
get("ImageData";
}
}

After coding the above lines only i came to know about "$eleMatch". I
have also posted new post regarding "$eleMatch".

Don't think i am wasting your time by asking same thing in two
different posts. But both have totally different context!!
and i have got the above solution(inefficient) for this problem. But,
still i am in need of knowing "How to use "eleMatch" in java driver?


Thanks again!!