具有改型和嵌套JSON响应的NPE

Question

I am using retrofit 1.9 and I'm having some trouble getting the values from nested JSON response. Here is the response

{
  "access_token": "83ebeabdec09f6670863766f792ead24d61fe3f9",
  "athlete": {
    "id": 227615,
    "resource_state": 3,
    ...
  }
}

I have a class to handle the response:

public class AuthResponse {

    String accessToken;
    StravaAthlete stravaAthlete;

    public AuthResponse(String accessToken, StravaAthlete stravaAthlete) {
        this.accessToken = accessToken;
        this.stravaAthlete = stravaAthlete;
    }

    public String getAccessToken() {
        return accessToken;
    }

    public StravaAthlete getStravaAthlete() {
        return stravaAthlete;
    }
}

and a class for the nested JSON object:

public class StravaAthlete {

    String id;

    public StravaAthlete(String id) {
        this.id = id;
    }

    public String getId() {
        return id;
    }
}

Unfortunately whenever I call authResponse.getStravaAthlete().getId() I get

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.drdp.rideart.api.model.StravaAthlete.getId()' on a null object reference

Not sure what I am doing wrong. I have retrofit logging set to full and can verify the information is in the response in the format I expect

Answer 1

accessToken and StravaAthlete are not key of your JSON. That's why you are getting null. You can either change them into access_token and athlete , or use the @SerializedName annotation. Eg

public class AuthResponse {

   @SerializedName("access_token")
   String accessToken;
   @SerializedName("athlete")
   StravaAthlete stravaAthlete;

Answer 2

首先，我可以在这里看到的是田径athlete的姓名，应该与您的班级stravaAthlete athlete匹配或添加注释@SerializedName(value="athlete")