Question

What is the best method to get the Mongo generated ID of a document inserted via Java.

Java进程插入文件是多面的,这意味着我们需要某种原样的办法来插入和归还物体的识别。

Also, if we setup a unique index, in the event that the object is a duplicate, will an ID be returned?

感谢!

Answer 1

Generate the ObjectId early, use it in the insert, and there will no need to have the database return it to you. ObjectId doesn t use a shared sequence number to be unique, so it doesn t matter if you generate one before inserting or retrieve it after.

public ObjectId createThing() {
    ObjectId result = new ObjectId();
    BasicDBObject thingToInsert = new BasicDbObject();
    thingToInsert.put( _id , result);
    //set other fields here
    collection.insert(thingToInsert);
    return result;
}

Answer 2

土地 Mongo产生的迷魂药在全球是独一无二的,可以从多面应用中安全使用。

generated ObjectId can be obtained from the DbObject under _id key.

If inserted document violates a unique index constraint - java driver may throw an exception, depending on a value of WriteConcern:

 http://api.mongodb.org/java/current/com/mongodb/WriteConcern.html

如果其价值更高,那么NORMAL-例外就会被推翻。

可以通过使用行文法,具体针对每个个人添加(或更新)方法,或在全球范围进行写作。

Answer 3

I retrieve the document with _id but when I get the data into my java class eg mobile, _id attribute which is of type ObjectID me I change it set the value of the document in mongodb.

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