How to use Jackson to deserialise list in java? - jackson2

Question

My Java Class is
public class User {
private List<UserInfo> userInfoList;
public class UserInfo {
private String id;
}
}
Let's assume it has getter, setter method.
json is
{"userInfoList" : [{"id":"a", "id":"b"}]}
I tried to deserialize it like below.
objectMapper.readValue(json, User.class);
But it throws error.
Can not construct instance of User$UserInfoList: no suitable constructor found
How to deserialize it?

Answer 1

I think you should make UserInfo static. Jackson cannot construct the UserInfo class.
I tried with that change and it works for me :
public class User {
private List<UserInfo> userInfoList;
public static class UserInfo {
private String id;
public UserInfo() {
super();
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
}
public List<UserInfo> getUserInfoList() {
return userInfoList;
}
public void setUserInfoList(List<UserInfo> userInfoList) {
this.userInfoList = userInfoList;
}
}
And :
public class App {
public static void main(String[] args) throws IOException {
ObjectMapper mapper = new ObjectMapper();
User.UserInfo ui1 = new User.UserInfo();
ui1.setId("a");
User.UserInfo ui2 = new User.UserInfo();
ui2.setId("b");
List<User.UserInfo> userInfoList = new ArrayList<User.UserInfo>();
userInfoList.add(ui1);
userInfoList.add(ui2);
User user = new User();
user.setUserInfoList(userInfoList);
System.out.println(mapper.writeValueAsString(user));
user = mapper.readValue(mapper.writeValueAsString(user), User.class);
}
}