Question

我正在尝试从Google Firestore检索对象，这是对象：

由于我添加了属性，因此使用该类对对象进行反序列化得到了错误信息：

@Data
public class Car {
    private String plate;
    private String model;
    private long km;
    private boolean available;
    private DocumentReference soat;   
}

此代码可从Firestore中检索所有Car对象

     @Override
    public List<Car> findAll() {
        List<Car> empList = new ArrayList<Car>();
        CollectionReference car = fb.getFirestore().collection("Cars");
        ApiFuture<QuerySnapshot> querySnapshot = car.get();
        try {
            for (DocumentSnapshot doc : querySnapshot.get().getDocuments()) {
                Car emp = doc.toObject(Car.class);
                empList.add(emp);
            }
        } catch (Exception e) {
             e.printStackTrace();
        }
        return empList;
    }

由于我添加了属性，因此在请求数据时出现此错误

错误7544-[nio-8080-exec-7] s.e.ErrorMvcAutoConfiguration $ StaticView：无法呈现请求[请求路由]和异常的错误页面[无法编写JSON：无限递归（StackOverflowError）；嵌套异常是com.fasterxml.jackson.databind.JsonMappingException：无限递归（StackOverflowError）（通过参考链：com.google.cloud.firestore.FirestoreImpl [“ options”]-> com.google.cloud.firestore.FirestoreOptions [“ service“]-> com.google.cloud.firestore.FirestoreImpl [” options“]-> com.google.cloud.firestore.FirestoreOptions [” service“]-> com.google.cloud.firestore.FirestoreImpl [” options“ ]-> com.google.cloud.firestore.FirestoreOptions [“服务”]-> com.google.cloud.firestore.FirestoreImpl [“ options”] ... -> com.google.cloud.firestore.FirestoreOptions [“ credentia [“ modulus”]）]），因为响应已经提交。结果，

以前我无法正确发出请求，所以我将其添加到了application.properties

spring.jackson.serialization.FAIL_ON_EMPTY_BEANS=false

编辑：只是尝试了此方法，仍然出现相同的错误

    @Override
    public List<Car> findAll() {
        List<Car> empList = new ArrayList<Car>();
        CollectionReference car = fb.getFirestore().collection("Cars");
        ApiFuture<QuerySnapshot> querySnapshot = car.get();
        try {
            for (DocumentSnapshot doc : querySnapshot.get().getDocuments()) {
               
                 String plate=doc.getData().get("plate").toString();
                 String model=doc.getData().get("model").toString();
                 long km=Long.parseLong(doc.getData().get("km").toString());
                 boolean available=Boolean.parseBoolean(doc.getData().get("available").toString());
                 DocumentReference soat=(DocumentReference)doc.getData().get("soat");

                Car emp = new Car();
                emp.setAvailable(available);
                emp.setKm(km);
                emp.setModel(model);
                emp.setPlate(plate);
                emp.setSoat(soat);

                empList.add(emp);
            }
        } catch (Exception e) {
             e.printStackTrace();
        }
        return empList;
    }

-------编辑--------
我已将此添加到我的application.properties

spring.jackson.serialization.fail-on-self-references=false

现在我可以从Firestore呼叫中获取

[{"plate":"HEO628","model":"2014","km":75000,"available":true,"soat":{"path":"SOATS/HEO628","parent":{"parent":null,"id":"SOATS","path":"SOATS","firestore":{"firestore":{"firestore":{"firestore":{"firestore":{"firestore":{"firestore":{"firestore":{"firestore":

Answer 1

基本上，您必须创建一个类来反序列化DatabaseReference，在这种情况下，类名将为SOAT，并使用它来存储对数据库的引用。

@Data
public class Car {
    private String plate;
    private String model;
    private long km;
    private boolean available;
    private SOAT soat;  
    private Insurance insurance;
    private Techno techno;
}

然后，从FireBase检索信息时，必须发出以下请求，以指定要映射的对象的类型。

public List<Car> findAll() {
        List<Car> empList = new ArrayList<Car>();
        CollectionReference car = fb.getFirestore().collection("Cars");
        ApiFuture<QuerySnapshot> querySnapshot = car.get();
        try {
            for (DocumentSnapshot doc : querySnapshot.get().getDocuments()) {

                String plate = doc.getData().get("plate").toString();
                String model = doc.getData().get("model").toString();
                long km = Long.parseLong(doc.getData().get("km").toString());
                boolean available = Boolean.parseBoolean(doc.getData().get("available").toString());
                DocumentSnapshot soatref = fb.getFirestore().collection("SOATS").document(plate).get().get();
                DocumentSnapshot technoref = fb.getFirestore().collection("Technos").document(plate).get().get();
                DocumentSnapshot insuranceref = fb.getFirestore().collection("Insurances").document(plate).get().get();
                SOAT soat = soatref.toObject(SOAT.class);
                Techno techno = technoref.toObject(Techno.class);
                Insurance insurance = insuranceref.toObject(Insurance.class);

                Car emp = new Car();
                emp.setAvailable(available);
                emp.setKm(km);
                emp.setModel(model);
                emp.setPlate(plate);
                emp.setSoat(soat);
                emp.setInsurance(insurance);
                emp.setTechno(techno);

                empList.add(emp);
            }
        } catch (Exception e) {

        }
        return empList;
    }

然后调用您所持有的API，就可以像这样正确地引用对象。

{
    "plate": "HEO628",
    "model": "2014",
    "km": 75000,
    "available": true,
    "soat": {
      "expeditionDate": "2020-09-29T06:12:12.000+00:00",
      "carPlate": "HEO628"
    },
    "insurance": {
      "expeditionDate": "2020-10-01T11:12:12.000+00:00",
      "carPlate": "HEO628"
    },
    "techno": {
      "expeditionDate": "2020-09-08T17:00:00.000+00:00",
      "carPlate": "HEO628"
    }
  }

如何从Firestore获取DocumentReference字段？

1 个答案: