java - 如何从Java中Mongodb中的数组中获取项目

Question

我对在 MongoDB 中创建应用程序完全陌生。所以我遇到了一个问题，我不确定如何从 Mongodb 的数组中检索项目。以下是示例

{
    "name": "Random Person",
    "age": 22,
    "address": "Address of the User",
    "likes":[{
        "like": 1,
        "comment": "Comment of the User",
        "description": "Some description"
    },
    {
        "like": 2,
        "comment": "Comment of the User",
        "description": "Some description"
    },
    {
        "like": 3,
        "comment": "Comment of the User",
        "description": "Some description"
    },
    ]
}

所以我想要的预期结果如下

Name: Random Person
address: Address of the User
Comment: [Comment of the User, Comment of the User, Comment of the User] (Assuming we have different data at each index retrieved from Mongodb)

下面是代码

MongoCursor<Document> cursor = collection.find().iterator();
            
Document data = null;

while(cursor.hasNext()) {
    data = cursor.next();
    

    String name = (String) data.get("name");
    String address = (String) data.get("address");


    data.get("likes"); // Not sure about this line
}

我尝试过使用 data.get("likes.comment");但它返回 null 作为输出。

Answer 1

应该这样做：

data.getList("likes", Map.class)
        .stream()
        .map(map -> map.get("comment"))
        .collect(Collectors.toList());

我鼓励您阅读 Java 驱动程序的 Javadocs。