Executing Mongo like Query (JSON)through Java

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执笔经年
执笔经年 2020-12-25 14:54

I was wondering if there is a way to execute mongo like query directly through Java i.e. we give mongoDB like query as a String to a function in Java driver for mongoDB as a

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  • 2020-12-25 15:28

    Yes, there is way, by passing the filter as a string. Example:

    BasicDBObject query = BasicDBObject.parse("{userId: {$gt: \"1\"}}");
    FindIterable<Document> dumps = crapCollection.find(query);
    

    You can Also use com.mongodb.util.JSON, but I don't recommend it. It's less descriptive.

    DBObject dbObject = (DBObject)JSON.parse("{userId: {$gt: \"1\"}}");
    

    Please notice that this might be vulnerable to SQL injections because you parse/build the filter yourself.

    I recommend using Jongo's parameterized query.

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  • 2020-12-25 15:36

    What you showed here is not JSON, it's Javascript code for embedded MongoDB Shell. If you need for some reason to execute the code inside Java environment you will have to embed Javascript engine (like Rhino) and implement compatible API.

    Otherwise you just need to convert JSON to DBObject and you can do this with JSON.parse() method or any other JSON-mapping library like Jackson. Note that MongoDB uses extended set of data types that are not present in JSON: http://www.mongodb.org/display/DOCS/Data+Types+and+Conventions

    UPD: Scott Hernandez pointed out about JSON.parse.

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  • I would recommend to use mongo-shell-like-query utility (jar). It allows you to write mongo queries in java (or scala) code using the same syntax as that of mongo command shell. To be more specific, you can write mongo queries in string format. It also supports advance features such as aggregation pipeline. Have a look at https://github.com/EqualExperts/mongo-shell-like-query

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  • 2020-12-25 15:40

    You can follow the example in the tutorial:

    http://www.mongodb.org/display/DOCS/Java+Tutorial#JavaTutorial-GettingASetofDocumentsWithaQuery

    Note their use a of (Basic)DBObject to create the query, not a string.

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  • 2020-12-25 15:47

    Take a look at the Jongo library - it will allow you to run even pretty advanced queries using the command-line syntax.

    It also uses a very fast GSON mapper to return your own objects back to you as the result of the query, instead of a list of BasicDBObjects.

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