java - Mongodb在java中查询嵌套文档

Question

我是 Mongodb 新手。我在 mongodb 中有以下数据集。

{
"_id": {
    "$oid": "563644f44b17ca12886440a9"
},
"data": [
    {
        "uid": 1,
        "character": " ",
        "unicode": 32,
        "color": -7309587
    },
    {
        "uid": 2,
        "character": "!",
        "unicode": 33,
        "color": -8911704
    },
    {
        "uid": 3,
        "character": "\"",
        "unicode": 34,
        "color": -1778539
    }

我正在尝试使用 _id 和字符从此字段检索颜色。我无法执行查询。

这是我尝试过的。

DBObject clause1 = new BasicDBObject("_id",new ObjectId(KEY1));  
                DBObject clause2 = new BasicDBObject("data.character",text[i]);    
                BasicDBList or = new BasicDBList();
                or.add(clause1);
                or.add(clause2);
                DBObject query = new BasicDBObject("$and", or);

此外，我在寻找在 mongodb-java 中查询 3.0.0+ api 的方法时遇到了很多问题。有人可以帮忙吗？

Answer 1

    MongoClient mongoClient = new MongoClient(new ServerAddress("localhost", 27017));
    MongoDatabase db = mongoClient.getDatabase("testDB");
    AggregateIterable<Document> iterable = db.getCollection("testCollection").aggregate(
            asList(new Document("$unwind", "$data"), new Document("$match", (new Document("_id", new ObjectId(
                    "5636f106b2acf98ecb033b98")).append("data.character", " "))), new Document("$project",
                    new Document("data.color", 1).append("_id", 0))));

    iterable.forEach(new Block<Document>()
    {
        @Override
        public void apply(final Document document)
        {
            System.out.println(document.toJson());
        }
    });

更多详情请查看MongoDB Documentation .