Check if there is an error in update/insert | MongoDB Java driver

Question

I want to check if an insert fails (due to unique=True index in the collection). If there is an error do something. Bellow is an example of my code.

DBCollection user...;
BasicDBObject Doc = new BasicDBObject(... );

String user_exists = user.insert(Doc).getError(); //insert the doc get error if any
if(user_exists!=null){ //any errors?
    user.update(new BasicDBObject(...)); // error exists so do smthng
}

The above as it is does not work. I believe that the String user_exists is always null. How can I make the above work?

I have seen similar SO questions and mention the WriteConcern which can be passed in the insert(). E.g.

coll.insert(dbObj, WriteConcern.SAFE);

sources: SO question or Mongo docs

However I do not know which one field should I pass (SAFE, ACKNOWLEDGED, UNACKNOWLEDGED etc..) in order to get the error. Maybe I'm pointed in the wrong direction.

I do not wish to raise an exception just to check if there is an error returned by the insert operation.

Could you rephrase "However I do not know which one field should I pass or handle the rest." as it makes little sense — Martin
– Martin, Commented Feb 5, 2014 at 21:44
Yes, the various WriteConcern fields are desribed in api.mongodb.org/java/current/com/mongodb/… — Martin
– Martin, Commented Feb 5, 2014 at 22:04
The com.mongodb.MongoException.DuplicateKey is unavoidable if the dbObj you are writing violates some unique key constraint. That is just now the Mongo driver works. We are always WriteConcern.SAFE here. — Bob Kuhar
– Bob Kuhar, Commented Feb 5, 2014 at 22:22

Ori Dar · Accepted Answer · 2014-02-05 22:12:50Z

2

If you are using WriteConcern.ACKNOWLEDGED (which I think is also SAFE) you don't need to pollute your code with error checking.

For ACKNOWLEDGED, the driver will automatically issue a getLastError command automatically and raise an exception if anything got wrong, for example duplicate index violation.

Starting from v2.10 of the Java Driver, the default Write Concern is ACKNOWLEDGED

EDIT

I do not wish to raise an exception just to check if there is an error returned by the insert operation.

You shouldn't do this, but in any case:

The insert method indeed returns WriteResult. If it's getError() is null, everything is OK, otherwise it returns something such as E11000 duplicate key error index:.... For this to work, you will have to use WriteConcern.UNACKNOWLEDGED

edited Feb 5, 2014 at 22:12

answered Feb 5, 2014 at 22:03

Ori Dar

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3 Comments

Diolor Over a year ago

Sweet but how can I run the .update()? I still want to run it if something goes wrong :)

Yngve Sneen Lindal Over a year ago

Does anyone know if this is documented on the MongoDB pages somewhere? I couldn't find it.

Russ Jackson Over a year ago

Find more info on write concerns here and the documentation on save can be found at api.mongodb.org/java/current/com/mongodb/DBCollection.html ; note that a MongoExcption is thrown, and it extends from RuntimeException

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