如何将新值附加到mongodb中的列表？

Question

我想在下面的“ CarList”数组中插入一个新元素。 我在项目中使用MongoDB和dropwizzard。

{
    "_id": "56aa6119bf78f37eee64697e",
    "name": "Jack",
    "occupation": "business*emphasized text* owner",
    "carList": [{
        "brand": "Ford",
        "cost": "$25000"
    }, {
        "brand": "Mazda",
        "cost": "$23000 "
    }]
}

我的POJO课程：

public class CarOwners {

    @ObjectId
    public String _id;
    public String name;
    public String occupation;
    public List<CarDetails> carList;
}

public class CarDetails
{
    public String brand;
    public String cost;
}

我的代码在carList中添加新条目：

CarDetails newCarInfo = new CarDetails();
newCarInfo.brand="Toyota";
newCarInfo.cost="$20000";

BasicDBObject ownerQuery = new BasicDBObject("name", "Jack");
carOwnerCollections.update(ownerQuery, new BasicDBObject("$addToSet", new BasicDBObject("carList",newCarInfo)));

我得到的错误：

org.codehaus.jackson.map.JsonMappingException: Can not instantiate value of type [simple type, class data.CarDetails] from JSON String; no single-String constructor/factory method (through reference chain: data.PropertyLedger["carList"])

从错误中我可以猜测到CarDetails类的接线是问题。 我不确定如何解决。 我曾在Mongo和类似的链接中更新嵌套文档，但找不到答案。

任何指针都会有所帮助。 谢谢。

Answer 1

尝试对MongoDB中的数组使用$push运算符进行操作。

BasicDBObject ownerQuery = new BasicDBObject("name", "Jack");
//Below code will insert the new object to the existing carList array
carOwnerCollections.update(ownerQuery, new BasicDBObject("$push", new BasicDBObject("carList",new BasicDBObject("brand","Toyota").append("cost","$20000"))));