Firebase中的用户组 [英] Group of users in firebase

问题描述

User 被定义为：

  public class User { 
私人字符串电子邮件; 
 private String uid; 
私人列表< Group>组; 
 $ b $ public User（String email，String uid）{
 this.email = email; 
 this.uid = uid; 
 this.groups = new ArrayList<>（）; 
 
 $ b $ public User（）{} 
 $ b public User（String email，String uid，ArrayList< Group> groups）{
 this.email =电子邮件; 
 this.uid = uid; 
 this.groups = groups; 
} 
 
 public String getEmail（）{
 return email; 
} 
 
 public String getUid（）{
 return uid; 
} 
 
公共列表< Group> getGroups（）{
返回组; 
} 
 $ b $ public void addGroup（Group group）{
 if（this.groups == null）{
 this.groups = new ArrayList<> ; 
} 
 this.groups.add（group）; 
 
 $ b  

群组


  public class Group {
 private List< User>会员; 
 
私人Group（）{
} 
 
公共群组（列表<用户>用户）{
 this.memberList = users; 
} 
 
 public void addMember（User member）{
 this.memberList.add（member）; 
} 
 
 public List< User> getMemberList（）{
 return memberList; 
 
 
 
 
 
 
当试图保存到firebase时，错误：
 
 $ p $  java.lang.NoClassDefFoundError：com / fasterxml / jackson / databind / JsonMappingException 
 at com.fasterxml .jackson.databind.ser.std.BeanSerializerBase.serializeFields（BeanSerializerBase.java:611）
  

是问题是使用循环引用还是Firebase无法以这种方式存储数据？解决方案

是的我认为问题是循环参考。在有循环引用的地方，总是有序列化的问题。

我们可以看到用户和组之间有双向关系。根据官方文档，您可以改进结构：

  {
users：{
user1：{
name：User 1，
groups：{
group1：true，
group2：true，
group3：true 
}，
user2 ：{
name：User 2，
groups：{
group2：true，
group3：true 
} 
 
 
 
group{b $ bgroup1：{
name：Group 1，
members：{
user1：true 
}，
group2：{
name：Group 2，
members ：{
user1：true，
user2：true 
}，
group3：{
name：Group 3， 
members：{
user1：true，
user2：true 
} 
}，
 ... 
} 
} 
  

A User is defined as:

public class User {
  private String email;
  private String uid;
  private List<Group> groups;

  public User(String email, String uid) {
    this.email = email;
    this.uid = uid;
    this.groups = new ArrayList<>();
  }

  public User() {}

  public User(String email, String uid, ArrayList<Group> groups) {
    this.email = email;
    this.uid = uid;
    this.groups = groups;
  }

  public String getEmail() {
    return email;
  }

  public String getUid() {
    return uid;
  }

  public List<Group> getGroups() {
    return groups;
  }

  public void addGroup(Group group) {
    if (this.groups == null) {
      this.groups = new ArrayList<>();
    }
    this.groups.add(group);
  }
}

Group is defined as:

public class Group {
  private List<User> memberList;

  private Group() {
  }

  public Group(List<User> users) {
    this.memberList = users;
  }

  public void addMember(User member) {
    this.memberList.add(member);
  }

  public List<User> getMemberList() {
    return memberList;
  }
}

When attempting to save to firebase, this gives a runtime error of:

java.lang.NoClassDefFoundError: com/fasterxml/jackson/databind/JsonMappingException
                                                                             at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:611)

Is the issue to do with circular references or is Firebase not able to store data in this way?

解决方案

Yes I think the issue is with Circular reference. Where there is Circular reference, there is always issue with serializing it.

As we can see you have two - way relationship between Users and Groups. According to official documentation you can improve the structure as:

{
  "users": {
    "user1": {
      "name": "User 1",
      "groups": {
         "group1": true,
         "group2": true,
         "group3": true
      },
    "user2": {
      "name": "User 2",
      "groups": {
         "group2": true,
         "group3": true
      }
    },
    ...
  },
  "groups": {
    "group1": {
      "name": "Group 1",
      "members": {
        "user1": true
      },
    "group2": {
      "name": "Group 2",
      "members": {
        "user1": true,
        "user2": true
      },
    "group3": {
      "name": "Group 3",
      "members": {
        "user1": true,
        "user2": true
      }
    },
    ...
  }
}

这篇关于Firebase中的用户组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！