MongoDB Java客户端存储"_id"在"replaceOne"上为null [英] MongoDB Java Client stores "_id" as null on "replaceOne"

问题描述

我们已经从2.11.1升级到

We have upgraded (from 2.11.1) to

            <groupId>org.mongodb</groupId>
            <artifactId>mongo-java-driver</artifactId>
            <version>3.4.1</version>

现在，当我们这样做时:

Now when we do this:

        UpdateOptions options = (new UpdateOptions()).upsert(true);
        BasicDBObject queryObject = new BasicDBObject("_id", newObject.get("_id"));
        //where newObject.get("_id") returns "null", i.e. same as
        //BasicDBObject queryObject = new BasicDBObject("_id", null);
        UpdateResult result = collection.replaceOne(queryObject, newObject, options);

将插入一个新的文档，该文档的"_id"设置为null(即使以前在该集合中不存在_id为null的对象).

will insert a new document with "_id" set to null (even though no object with _id of null existed previously in the collection). When we do

        collection.insertOne(newObject);

相反，会生成一个正确的"_id".为什么"replaceOne"不能生成正确的_id?

instead then a proper "_id" is generated. Why does "replaceOne" does not generate a proper _id?

推荐答案

replaceOne的预期行为.

MongoDB会将_id字段添加到替换文档(如果替换的话) 过滤器或更换文件中未指定.如果_id为 两者中的值必须相等.

MongoDB will add the _id field to the replacement document if it is not specified in either the filter or replacement documents. If _id is present in both, the values must be equal.

因此，在创建新文档时，它将_id用作null.

So it uses the _id as null when creating a new document.

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