![Firebase中的用户组]( "Firebase中的用户组")
本文介绍了Firebase中的用户组的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
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，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！