Mongodb-java如何将新对象插入数组对象的起始索引

Question

I have a collection with following schema,

        {
                "_id" : ObjectId("58b9d6b9e02fd02963b7d227"),
                "id" : 1,
                "ref" : [
                        {
                                "no" : 101
                        },
                        {
                                "no" : 100
                        }
                        ]
        }

when i tried to push the child Object to ArrayList of Object ,it added into end of array , but my goal is push the object into start index of an array, I tried with this code but it insert the object into end of array failed,

Java code,

            Document push = new Document().append("$push", new Document().append("ref", new Document().append("no", 102)));
            collection.updateMany(new Document().append("id", 1), push);

ExpectedResult should be,

            {
                    "_id" : ObjectId("58b9d6b9e02fd02963b7d227"),
                    "id" : 1,
                    "ref" : [
                            {
                                    "no" : 102
                            },
                            {
                                    "no" : 101
                            },
                            {
                                    "no" : 100
                            }
                            ]
            }

Answer 1

Use $position modifier to specify the location in the array.

Mongodb-Java driver,

ArrayList<Document> docList = new ArrayList<Document>();
docList.add(new Document().append("no", 102));
Document push = new  Document().append("$push", new Document().append("ref", new Document().append("$each", docList).append("$position", 0)));
collection.updateMany(new Document().append("id", 1), push);