問題描述
如何使用 Java MongoDB 驅動程序檢索字段子集? (How to retrieve a subset of fields using the Java MongoDB driver?)
new poster here, I found this previous post but it's on C#, I tried doing this query straight into the java code of a JSP page, for some reason, it doesn't accept the info in the {} of the find() query and just gives out an error...
So peeps, how do I do this in Java:
// retrieve ssn field for documents where last_name == 'Smith':
db.users.find({last_name: 'Smith'}, {'ssn': 1});
Thanks!
PS: why the hell does C# have the nice little .Exclude() and .Include() commands and java doesn't? cries
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參考解法
方法 1:
The java driver follows the exact same API as the shell. Just pass a DBObject
containing your field projection as the second argument to find
or findOne
As far as I know the official C# driver doesn't expose Include() and Exclude() methods as they violate the standard API.
(by Gonçalo Vieira、Brendan W. McAdams)