Question

我正在尝试使用morphia做一个简单的findOne（）。我的代码如下：

public static void main(String[] args)
{
    MongoClient client = new MongoClient();
    Morphia morphia = new Morphia();
    morphia.map(Restaurant_M.class);
    Datastore ds = morphia.createDatastore(client, "test");
    System.out.println(ds.find(Restaurant_M.class).get());
    client.close();
}

我打印出一个null。我无法找到什么问题。有人能指出我正确的方向吗？感谢。

EDIT 收集格式

{
    "_id" : ObjectId("572eb5df1d739cc73c21f953"),
    "address" : {
            "building" : "469",
            "coord" : [
                    -73.961704,
                    40.662942
            ],
            "street" : "Flatbush Avenue",
            "zipcode" : "11225"
    },
    "borough" : "Brooklyn",
    "cuisine" : "Hamburgers",
    "grades" : [
            {
                    "date" : ISODate("2014-12-30T00:00:00Z"),
                    "grade" : "A",
                    "score" : 8
            },
            {
                    "date" : ISODate("2014-07-01T00:00:00Z"),
                    "grade" : "B",
                    "score" : 23
            },
            {
                    "date" : ISODate("2013-04-30T00:00:00Z"),
                    "grade" : "A",
                    "score" : 12
            },
            {
                    "date" : ISODate("2012-05-08T00:00:00Z"),
                    "grade" : "A",
                    "score" : 12
            }
    ],
    "name" : "Wendy'S",
    "restaurant_id" : "30112340"
}

@Entity class

@Entity("restaurants")
public class Restaurant_M
{
    @Id
    public ObjectId _id;
    @Property("borough")
    public String town;
    public String cuisine;
    public String name;
    @Property("restaurant_id")
    public String r_id;

Answer 1

问题是您没有提供有关该实体的所有信息你可以用来映射到实体： dt.getCollection（Restaurant_M.class）;然后使用DBObject 要么 dt.createQuery（Restaurant_M.class）.field（＆＃34;＆＃34;）。equal（＆＃34;指定＆＃34;）。get;

Answer 2

我按如下方式进行了DBO实现：

 public Restaurant_M getByID (String id)
 {
    Query<Restaurant_M> query = createQuery().field("cuisine").equal(id);
    return query.get();
 }

并更新了主要方法，如下所示

public static void main(String[] args)
{
    MongoClient client = new MongoClient("127.0.0.1:27017");
    Morphia morphia = new Morphia();
    Datastore ds = morphia.createDatastore(client, "test");
    RestaurantDAO rdao = new RestaurantDAOImpl(Restaurant_M.class, ds);
    Restaurant_M r = rdao.getByID("Hamburgers");
    System.out.println(r);

    r = ds.find(Restaurant_M.class).get();
    System.out.println (r);

}

使用我的JAVA类

2 个答案: