How to convert Jsonobject to a java class

Question

Greetings to all,

I’m developing an app that takes the return of a webservice to be used in this application as login data among others. I would like to ask for your guidance on how best to convert the data that is in a Jsonobject object to a class that stores all this API return information.

Json has the structure below:

{
"token": "N02156564365034657289&(*&*&$#",
"success": true,
"timezone": "America/Bahia",
"user": {
    "name": "Fulano de roça",
    "email": "[email protected]",
    "photo": ""
},
"msg": "Autenticado com sucesso"

}

I created a class to receive the data based on this json above:

public class RetornoServer {

private String mToken;
private boolean mSuccess;
private Usuario mUser;
private String mMsg;

public RetornoServer() {
}

public RetornoServer(String Token, boolean Success, Usuario User, String Msg) {
    this.mToken = Token;
    this.mSuccess = Success;
    this.mUser = User;
    this.mMsg = Msg;
}

public String getmToken() {
    return mToken;
}

public void setmToken(String mToken) {
    this.mToken = mToken;
}

public boolean ismSuccess() {
    return mSuccess;
}

public void setmSuccess(boolean mSuccess) {
    this.mSuccess = mSuccess;
}

public Usuario getmUser() {
    return mUser;
}

public void setmUser(Usuario mUser) {
    this.mUser = mUser;
}

public String getmMsg() {
    return mMsg;
}

public void setmMsg(String mMsg) {
    this.mMsg = mMsg;
}

@Override
public String toString() {
    return "RetornoServer{" +
            "mToken='" + mToken + '\'' +
            ", mSuccess=" + mSuccess +
            ", mUser=" + mUser +
            ", mMsg='" + mMsg + '\'' +
            '}';
}

}

I am using Retrofit 2 in connection with the webservice and the return is coming all right, this already feeding the Jsonobject object as shown below:

JsonObject responseJson = response.body();

I tried to convert using Gson, but it didn’t work

Gson gson = new Gson();
RetornoServer retornoServer = gson.fromJson(responseJson, RetornoServer.class);

Finally, if possible I would like your guidance on some material that I should read or some suggestion. I thank you in advance!

Answer 1

Gson is one of many libraries that convert JSON to objects. In your case, your attributes are all null because you could not find the fields of your object with the names of the JSON fields. For example:

public class RetornoServer {

private String token;
private boolean success;
private Usuario user;
private String msg;
(...)

More information here (taken from the Gson repository itself). You can notice that when the JSON attributes have underline (_), attributes of the Java Object also have.