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查询MongoDB中的数组位置?

mongodb java

user405398 · 技术社区 · 15 年前

我正在使用MavigDB的Java驱动程序。我有一份文件, AlbumName , PreviewSize , ThumbSize , _id 和; Comments . 预览尺寸 和; 拇指尺寸 是数组。我想知道如何查询这个文档并获取任何特定的数组值。

更清楚地说,我的文件是这样的,

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" : [ ]}

我怎样才能拿到 TomJerry2_468x342.jpg 及其 <Binary Data> 从 预览尺寸 .

我是MongoDB的新手。我不知道是否可能。我刚刚构建了这个文档,我可以用新的图像更新这个文档。我从中学到这个 this 演示。

我的问题是我怎样才能得到任何具体的 <二进制数据 当我知道它的名字?

任何建议都会更有价值!

谢谢!!!!

更新

例如:/,我尝试的代码,

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();
     System.out.println("Result Size: "+i);
     System.out.println(result);

     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>.*/

首先,我尝试了用(basicdbobject)进行强制转换,但我给了我一个错误,比如, cannot cast (BasicBSONList) to (BasicDBObject) 然后我把它改成 (BasicBSONList)

我想我在接受器上做错了。我应该用什么接收器!!!!????

我尝试了上面的一个,在控制台中得到的错误消息是,

控制台显示:

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"}}

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

我对MongoDB完全陌生,就像3天大的时候一样:(……给我一条路出去!!!!!

我还想知道是否有任何方法可以检索特定的数据, 比如,如果我知道 ImageName 我能得到它的 BinaryData??

1 回复 | 直到 15 年前

Gates VP 15 年前

db.albums.find({ "ThumbSize.ImageName" : "TomJerry2_468x342.jpg"} )

db.albums.find({ "ThumbSize.ImageName" : "TomJerry2_468x342.jpg"}, { "ThumbSize" : 1 } )