如何在mongodb的单个字段中添加值答案

【问题标题】：how to add values in a single field in mongodb如何在mongodb的单个字段中添加值
【发布时间】：2015-12-01 14:53:38
【问题描述】：

我在 mongodb 中有以下文档

{
"_id" : "1999",
    "Email" : "mail@example.com",
    "FirstName" : "personFirstNmae",
    "LastName" : "personLastName",
    "UserStatus" : "INACTIVE",

    "FollowingItems" : [
        {
            "FollowingItemUuid" : "g12345",
            "FollowingItemUuidType" : "GALLERY"
        }
    ]
}

我想实现这个

{
"_id" : "1999",
    "Email" : "mail@example.com",
    "FirstName" : "personFirstNmae",
    "LastName" : "personLastName",
    "UserStatus" : "INACTIVE",

    "FollowingItems" : [
        {
            "FollowingItemUuid" : "g12345",
            "FollowingItemUuidType" : "GALLERY"
        },
        {
            "FollowingItemUuid" : "M121",
            "FollowingItemUuidType" : "MUSEUM"
        }


    ]
}

这是我的代码

val q=QueryBuilder.start("_id").is("1999")
var update=collection.update(q.get,new BasicDBObject("$set",new BasicDBObject("FollowingItems.$.FollowingItemUuid","M121").append("FollowingItems.$.FollowingItemUuidType","MUSEUM")))

但它会引发以下异常

com.mongodb.WriteConcernException: { "serverUsed" : "Localhost:27017" , "ok" : 1 , "n" : 0 , "updatedExisting" : false , "err" : "cannot use the part (FollowingItems of FollowingItems.FollowingItemUuid) to traverse the element ({FollowingItems: [ { FollowingItemUuid: \"g12345\", FollowingItemUuidType: \"GALLERY\" } ]})" , "code" : 16837}
    at com.mongodb.CommandResult.getWriteException(CommandResult.java:90)
    at com.mongodb.CommandResult.getException(CommandResult.java:79)
    at com.mongodb.DBCollectionImpl.translateBulkWriteException(DBCollectionImpl.java:316)
    at com.mongodb.DBCollectionImpl.update(DBCollectionImpl.java:274)
    at com.mongodb.casbah.MongoCollectionBase$class.update(MongoCollection.scala:882)
    at com.mongodb.casbah.MongoCollection.update(MongoCollection.scala:1162)

请指导我如何实现我的预期结果以及我做错了什么

【问题讨论】：

标签： java mongodb scala scala-2.11

【解决方案1】：

您需要使用$push 运算符来使用它。这是 MongoDB shell 命令：

  db.data.update({
  "_id": "1999"
 }, {
  "$push": {
    "FollowingItems": {
      "FollowingItemUuid": "M121",
      "FollowingItemUuidType": "MUSEUM"
    }
  }
})

这是等效的 QueryBuilder 语法：

val q=QueryBuilder.start("_id").is("1999")
var update=collection.update(q.get,new BasicDBObject("$push",new BasicDBObject("FollowingItems.$.FollowingItemUuid","M121").append("FollowingItems.$.FollowingItemUuidType","MUSEUM")))

【讨论】：