大家好，我正在使用 java 在 mongodb 上工作，我有一个场景，如果外部文档匹配，那么我必须在嵌套数组中更新/添加计数，例如我想做这样的事情:

`"_id" : ObjectId("55d71603aed7562284e5df95"),
"id" : "1",
"type" : "a",
"score" : {
        "mark1" : "1",
        "mark2" : "2",
        "count" : { "one","two"                
        }
}`

如果我再次发送具有相同字段(如 id:1、type:a、mark1:1、mark2:2)的文档，那么我必须将我的文档作为

`"_id" : ObjectId("55d71603aed7562284e5df95"),
"id" : "1",
"type" : "a",
"score" : {
        "mark1" : "1",
        "mark2" : "2",
        "count" : { "one","two","three"                
        }
}`

但是我得到了这样的东西:

`"_id" : ObjectId("55d71e42aed7560e8c9d02e4"),
"id" : "1",
"type" : "a",
"score" : {
        "mark1" : "1",
        "mark2" : "2",
        "count" : {
                "count" : "one",

        }
}`

我的java代码是

 `mongoDatabase=mongoClient.getDatabase("TestNestedInsert");
        Document sourceDocument=mongoDatabase.getCollection("entity").find(new Document("id",1).append("score.mark1", "1").append("score.mark2", "2")).first();
        if(sourceDocument==null){
            Document entity=new Document();
            entity.append("id", "1");
            entity.append("type", "a");
            entity.append("score", new Document("mark1","1").append("mark2", "2").append("count", new Document("count","one")));
            mongoDatabase.getCollection("entity").insertOne(entity);
        }
        else{
            mongoDatabase.getCollection("entity").findOneAndUpdate(new Document("id",1).append("score.mark1", "1").append("score.mark2", "2"), new Document("$set",new Document("score.count","three")));
        }
        ` 

我知道我们不能有重复的键我也尝试了 $set 和 $push 但我被卡住了。有什么帮助吗？

最佳答案

主要问题是，根据代码，“count”键是一个对象而不是数组。所以正确的 JSON 表示是:

{
    "_id": ObjectId("55d71603aed7562284e5df95"),
    "id": "1",
    "type": "a",
    "score": {
        "mark1": "1",
        "mark2": "2",
        "count": [
            "one",
            "two",
            "three"
        ]
    }
}

注意“计数”键后的方括号“[]”。

我对新的 mongo java 驱动程序 (3.0) 有同样的问题。 这是我解决它的方法:

MongoDatabase mongoDatabase = mongoClient.getDatabase("TestNestedInsert");
MongoCollection<Document> entityCollection = mongoDatabase.getCollection("entity");

Document queryDocument = new Document("id", 1).append("score.mark1", "1").append("score.mark2", "2");
Document sourceDocument = entityCollection.find(queryDocument).first();

if (sourceDocument == null) {
    Document entity = new Document();
    entity.append("id", "1");
    entity.append("type", "a");

    // Create the score nested object
    String[] countArray = { "one", "two" }; // create the count array
    Document scoreObject = new Document()
            .append("mark1", "1")
            .append("mark2", "2")
            .append("count", countArray); // append the count array

    entity.append("score", scoreObject); // append the score object.
    entityCollection.insertOne(entity);
}
else{
    // push the new element to the count array.
    // see: https://docs.mongodb.org/v3.0/reference/operator/update/push/#append-a-value-to-an-array
    Document elementToArray = new Document("score.count", "three");
    Document pushElement = new Document("$push", elementToArray);
    entityCollection.updateOne(queryDocument, pushElement);
}

希望对您有所帮助!

关于java - 如何使用java在mongodb中的嵌套数组中添加元素，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/32140952/