EddyLee EddyLee - 1 year ago 90
JSON Question

Convert Json to List Java

I have a JSON array like this :

{"_id": {"$oid":"57e9e4b1f36d281c4b330509"}, "user": "edmtdev" },
{"_id": {"$oid":"57e9e4cec2ef164375c4c292"}, "user": "admin1234" },
{"_id": {"$oid":"57ea1b0ac2ef164375c5ff1e"}, "username": "admin34" }

This is my
, used to store all data:

public class User{
private Id id;
private String user;

public Id getId() {
return id;

public void setId(Id id) {
this.id = id;

public String getUser() {
return user;

public void setUser(String user) {
this.user = user;

And my
, used to store the ID:

public class Id {

private String $oid;

public String get$oid() {
return $oid;

public void set$oid(String $oid) {
this.$oid = $oid;

I am using
in Java to get my users as a

List<User> users = new ArrayList<User>();
Gson gson = new Gson();
Type listType = new TypeToken<List<User>>(){}.getType();
users = gson.fromJson(s,listType);

The problem is, I get users with username but no ID, $oid is not registered. Can someone help me understanding what does not work in this piece of code ?

Answer Source

You must replace id in User class by:

private Id _id;

because your json is _id, not id. And your json string at the end is wrong, is user, not username

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