如何从Firestore获取DocumentReference字段？

huangapple
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英文:

How do I get a DocumentReference field from Firestore?

问题

以下是翻译好的内容：

我正在尝试从 Google Firestore 检索一个对象，这是该对象：

Firestore对象

由于我添加了属性 "soat"，我在使用以下类对对象进行反序列化时遇到错误：

  1. @Data
  2. public class Car {
  3.     private String plate;
  4.     private String model;
  5.     private long km;
  6.     private boolean available;
  7.     private DocumentReference soat;   
  8. }

以及用于从 Firestore 检索所有 Car 对象的代码：

  1. @Override
  2. public List<Car> findAll() {
  3.     List<Car> empList = new ArrayList<Car>();
  4.     CollectionReference car = fb.getFirestore().collection("Cars");
  5.     ApiFuture<QuerySnapshot> querySnapshot = car.get();
  6.     try {
  7.         for (DocumentSnapshot doc : querySnapshot.get().getDocuments()) {
  8.             Car emp = doc.toObject(Car.class);
  9.             empList.add(emp);
  10.         }
  11.     } catch (Exception e) {
  12.          e.printStackTrace();
  13.     }
  14.     return empList;
  15. }

由于我添加了属性 "soat"，当请求数据时我遇到了这个错误：

ERROR 7544 --- [nio-8080-exec-7] s.e.ErrorMvcAutoConfiguration$StaticView : 无法为请求 [请求路由] 和异常 [无法写入 JSON：无限递归 (StackOverflowError)；嵌套异常是 com.fasterxml.jackson.databind.JsonMappingException：无限递归 (StackOverflowError) (通过引用链：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["service"]->com.google.cloud.firestore.FirestoreImpl["options"]...
->com.google.cloud.firestore.FirestoreOptions["modulus"]]) 渲染错误页面，因为响应已经被提交。因此，

以前我无法正确进行请求，因此我在我的 application.properties 中添加了以下内容：

  1. spring.jackson.serialization.FAIL_ON_EMPTY_BEANS=false

编辑：刚刚尝试了这个方法，仍然遇到相同的错误

  1. @Override
  2. public List<Car> findAll() {
  3.     List<Car> empList = new ArrayList<Car>();
  4.     CollectionReference car = fb.getFirestore().collection("Cars");
  5.     ApiFuture<QuerySnapshot> querySnapshot = car.get();
  6.     try {
  7.         for (DocumentSnapshot doc : querySnapshot.get().getDocuments()) {
  8.            
  9.              String plate = doc.getData().get("plate").toString();
  10.              String model = doc.getData().get("model").toString();
  11.              long km = Long.parseLong(doc.getData().get("km").toString());
  12.              boolean available = Boolean.parseBoolean(doc.getData().get("available").toString());
  13.              DocumentReference soat = (DocumentReference) doc.getData().get("soat");
  15.             Car emp = new Car();
  16.             emp.setAvailable(available);
  17.             emp.setKm(km);
  18.             emp.setModel(model);
  19.             emp.setPlate(plate);
  20.             emp.setSoat(soat);
  22.             empList.add(emp);
  23.         }
  24.     } catch (Exception e) {
  25.          e.printStackTrace();
  26.     }
  27.     return empList;
  28. }

-------编辑--------

我已将以下内容添加到我的 application.properties 文件中

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

现在我从 Firestore 调用中获得了以下内容：

  1. [{"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":...
英文:

Im trying to retrieve an object from a google Firestore, this is the object:

Firestore object

Since i added the atribute soat im getting erros im using this class to deserialize the object:

  1. @Data
  2. public class Car {
  3.     private String plate;
  4.     private String model;
  5.     private long km;
  6.     private boolean available;
  7.     private DocumentReference soat;   
  8. }

And this code to retrieve the all the Car objects from the Firestore

  1.      @Override
  2.     public List&lt;Car&gt; findAll() {
  3.         List&lt;Car&gt; empList = new ArrayList&lt;Car&gt;();
  4.         CollectionReference car = fb.getFirestore().collection(&quot;Cars&quot;);
  5.         ApiFuture&lt;QuerySnapshot&gt; querySnapshot = car.get();
  6.         try {
  7.             for (DocumentSnapshot doc : querySnapshot.get().getDocuments()) {
  8.                 Car emp = doc.toObject(Car.class);
  9.                 empList.add(emp);
  10.             }
  11.         } catch (Exception e) {
  12.              e.printStackTrace();
  13.         }
  14. 		return empList;
  15.     }

Since i added the property soat im getting this error whe requesting the data

> ERROR 7544 --- [nio-8080-exec-7] s.e.ErrorMvcAutoConfiguration$StaticView : Cannot render error page for request [request route] and exception [Could not write JSON: Infinite recursion (StackOverflowError); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: 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["service"]->com.google.cloud.firestore.FirestoreImpl["options"]...
> ->com.google.cloud.firestore.FirestoreOptions["credentia
["modulus"])] as the response has already been committed. As a result,

Previously i couldnt make the request properly so i added this to my application.properties

  1. spring.jackson.serialization.FAIL_ON_EMPTY_BEANS=false

Edit: just tried this aproach and still getting same error

  1.     @Override
  2.     public List&lt;Car&gt; findAll() {
  3.         List&lt;Car&gt; empList = new ArrayList&lt;Car&gt;();
  4.         CollectionReference car = fb.getFirestore().collection(&quot;Cars&quot;);
  5.         ApiFuture&lt;QuerySnapshot&gt; querySnapshot = car.get();
  6.         try {
  7.             for (DocumentSnapshot doc : querySnapshot.get().getDocuments()) {
  8.                
  9.                  String plate=doc.getData().get(&quot;plate&quot;).toString();
  10.                  String model=doc.getData().get(&quot;model&quot;).toString();
  11.                  long km=Long.parseLong(doc.getData().get(&quot;km&quot;).toString());
  12.                  boolean available=Boolean.parseBoolean(doc.getData().get(&quot;available&quot;).toString());
  13.                  DocumentReference soat=(DocumentReference)doc.getData().get(&quot;soat&quot;);
  15.                 Car emp = new Car();
  16.                 emp.setAvailable(available);
  17.                 emp.setKm(km);
  18.                 emp.setModel(model);
  19.                 emp.setPlate(plate);
  20.                 emp.setSoat(soat);
  22.                 empList.add(emp);
  23.             }
  24.         } catch (Exception e) {
  25.              e.printStackTrace();
  26.         }
  27. 		return empList;
  28.     }

-------EDIT--------<br>
I have aded this to my application.properties

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

And now i get this from the Firestore call

  1. [{&quot;plate&quot;:&quot;HEO628&quot;,&quot;model&quot;:&quot;2014&quot;,&quot;km&quot;:75000,&quot;available&quot;:true,&quot;soat&quot;:{&quot;path&quot;:&quot;SOATS/HEO628&quot;,&quot;parent&quot;:{&quot;parent&quot;:null,&quot;id&quot;:&quot;SOATS&quot;,&quot;path&quot;:&quot;SOATS&quot;,&quot;firestore&quot;:{&quot;firestore&quot;:{&quot;firestore&quot;:{&quot;firestore&quot;:{&quot;firestore&quot;:{&quot;firestore&quot;:{&quot;firestore&quot;:{&quot;firestore&quot;:{&quot;firestore&quot;:

答案1

得分: 1

基本上，您需要创建一个类来反序列化您的 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。

  1. @Data
  2. public class Car {
  3.     private String plate;
  4.     private String model;
  5.     private long km;
  6.     private boolean available;
  7.     private SOAT soat;  
  8.     private Insurance insurance;
  9.     private Techno techno;
  10. }

然后在从 FireBase 检索信息时，您需要进行以下请求，以便指定要映射的对象类型。

  1. public List<Car> findAll() {
  2.     List<Car> empList = new ArrayList<Car>();
  3.     CollectionReference car = fb.getFirestore().collection("Cars");
  4.     ApiFuture<QuerySnapshot> querySnapshot = car.get();
  5.     try {
  6.         for (DocumentSnapshot doc : querySnapshot.get().getDocuments()) {
  8.             String plate = doc.getData().get("plate").toString();
  9.             String model = doc.getData().get("model").toString();
  10.             long km = Long.parseLong(doc.getData().get("km").toString());
  11.             boolean available = Boolean.parseBoolean(doc.getData().get("available").toString());
  12.             DocumentSnapshot soatref = fb.getFirestore().collection("SOATS").document(plate).get().get();
  13.             DocumentSnapshot technoref = fb.getFirestore().collection("Technos").document(plate).get().get();
  14.             DocumentSnapshot insuranceref = fb.getFirestore().collection("Insurances").document(plate).get().get();
  15.             SOAT soat = soatref.toObject(SOAT.class);
  16.             Techno techno = technoref.toObject(Techno.class);
  17.             Insurance insurance = insuranceref.toObject(Insurance.class);
  19.             Car emp = new Car();
  20.             emp.setAvailable(available);
  21.             emp.setKm(km);
  22.             emp.setModel(model);
  23.             emp.setPlate(plate);
  24.             emp.setSoat(soat);
  25.             emp.setInsurance(insurance);
  26.             emp.setTechno(techno);
  28.             empList.add(emp);
  29.         }
  30.     } catch (Exception e) {
  32.     }
  33.     return empList;
  34. }

然后在调用您的 API 时，您应该获得一个正确的对象引用，如下所示。

  1. {
  2.     "plate": "HEO628",
  3.     "model": "2014",
  4.     "km": 75000,
  5.     "available": true,
  6.     "soat": {
  7.         "expeditionDate": "2020-09-29T06:12:12.000+00:00",
  8.         "carPlate": "HEO628"
  9.     },
  10.     "insurance": {
  11.         "expeditionDate": "2020-10-01T11:12:12.000+00:00",
  12.         "carPlate": "HEO628"
  13.     },
  14.     "techno": {
  15.         "expeditionDate": "2020-09-08T17:00:00.000+00:00",
  16.         "carPlate": "HEO628"
  17.     }
  18. }
英文:

Basically you have to create a class to deserialice your DatabaseReference, in this case the class name would be SOAT and use it to sotre your reference to the database.

  1. @Data
  2. public class Car {
  3. private String plate;
  4. private String model;
  5. private long km;
  6. private boolean available;
  7. private SOAT soat;  
  8. private Insurance insurance;
  9. private Techno techno;
  10. }

Then when retrieving the information from FireBase you have to make the following requests in order to specify the kind of object your are going to map.

  1. public List&lt;Car&gt; findAll() {
  2. List&lt;Car&gt; empList = new ArrayList&lt;Car&gt;();
  3. CollectionReference car = fb.getFirestore().collection(&quot;Cars&quot;);
  4. ApiFuture&lt;QuerySnapshot&gt; querySnapshot = car.get();
  5. try {
  6. for (DocumentSnapshot doc : querySnapshot.get().getDocuments()) {
  7. String plate = doc.getData().get(&quot;plate&quot;).toString();
  8. String model = doc.getData().get(&quot;model&quot;).toString();
  9. long km = Long.parseLong(doc.getData().get(&quot;km&quot;).toString());
  10. boolean available = Boolean.parseBoolean(doc.getData().get(&quot;available&quot;).toString());
  11. DocumentSnapshot soatref = fb.getFirestore().collection(&quot;SOATS&quot;).document(plate).get().get();
  12. DocumentSnapshot technoref = fb.getFirestore().collection(&quot;Technos&quot;).document(plate).get().get();
  13. DocumentSnapshot insuranceref = fb.getFirestore().collection(&quot;Insurances&quot;).document(plate).get().get();
  14. SOAT soat = soatref.toObject(SOAT.class);
  15. Techno techno = technoref.toObject(Techno.class);
  16. Insurance insurance = insuranceref.toObject(Insurance.class);
  17. Car emp = new Car();
  18. emp.setAvailable(available);
  19. emp.setKm(km);
  20. emp.setModel(model);
  21. emp.setPlate(plate);
  22. emp.setSoat(soat);
  23. emp.setInsurance(insurance);
  24. emp.setTechno(techno);
  25. empList.add(emp);
  26. }
  27. } catch (Exception e) {
  28. }
  29. return empList;
  30. }

An then whe calling your API you shold get a proper reference to the Object like this.

  1. {
  2. &quot;plate&quot;: &quot;HEO628&quot;,
  3. &quot;model&quot;: &quot;2014&quot;,
  4. &quot;km&quot;: 75000,
  5. &quot;available&quot;: true,
  6. &quot;soat&quot;: {
  7. &quot;expeditionDate&quot;: &quot;2020-09-29T06:12:12.000+00:00&quot;,
  8. &quot;carPlate&quot;: &quot;HEO628&quot;
  9. },
  10. &quot;insurance&quot;: {
  11. &quot;expeditionDate&quot;: &quot;2020-10-01T11:12:12.000+00:00&quot;,
  12. &quot;carPlate&quot;: &quot;HEO628&quot;
  13. },
  14. &quot;techno&quot;: {
  15. &quot;expeditionDate&quot;: &quot;2020-09-08T17:00:00.000+00:00&quot;,
  16. &quot;carPlate&quot;: &quot;HEO628&quot;
  17. }
  18. }

huangapple
  • 本文由 发表于 2020年10月5日 03:11:45
  • 转载请务必保留本文链接：https://go.coder-hub.com/64198805.html
  • firebase
  • google-cloud-firestore
  • java
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