查询MongoDB集合中的字段。 [英] Query fields in a MongoDB Collection.

问题描述

我正在尝试查询mongodb集合中的特定字段。这是我的代码和输出：

I am trying to query specific fields in a mongodb collection. Here is my code and output:

    Mongo m = new Mongo();
    DB db = m.getDB( "mydb" );
    DBCollection coll = db.getCollection("student") ;


    // adding data 
    BasicDBObject moz = new BasicDBObject();
    moz.put("Name", "Mozammil");
    coll.insert(moz);



    DBCursor cursor = coll.find();


    while (cursor.hasNext()) {
        System.out.println(cursor.next());

    }

这将返回以下内容：

{ "_id" : { "$oid" : "4f5a4477c5e80f71ece56797"} , "Name" : "Mozammil"}

但是，我只想要Name部分。谷歌搜索，这应该做的工作。

However, i want only the Name part. Googling around, this should do the job.

    DBCursor cursor = coll.find({}, {'Name':1});


    while (cursor.hasNext()) {
        System.out.println(cursor.next());
    }

但它不起作用。请帮忙？

But it is not working. Help please?

推荐答案

您可以通过光标使用get返回的文档来获取您要查找的字段。像这样：

You can use get on the returned document by the cursor to get the field you are looking for. Like this:

System.out.println(cursor.next().get("key"));

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