CODEWITHSUNDEEP
androidjsonweb-servicesgson
FernandoPaiva
FernandoPaiva

Reputation: 4460

Converting Gson to Object?

I'm trying use Gson to use with a JSON return of a Web Service. That is JSON return this format: 

{
  "cod":999,
  "msg":"User Data.",
  "return":{
    "ID":"74",
    "name":"FERNANDO PAIVA",
    "devices":[]
  }
}

When I try use gson.fromJson(json_return, MyObject.class doesn't works and thrown an exception. I'm follow this user guide: https://sites.google.com/site/gson/gson-user-guide#TOC-Using-Gson

How can I do this ?

I'm trying this.

public class User implements Serializable{
    private static final long serialVersionUID = 1L;

    @SerializedName("ID")
    private Long id;

    private String name;

    //get and set
}

/** get informations of web service */
public static String get(String url){       
        String s = null;

        try {
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpResponse httpResponse = httpClient.execute(new HttpGet(url));
            HttpEntity entity = httpResponse.getEntity();
            if(entity != null){
                s = EntityUtils.toString(entity);                           
            }           
        } catch (ClientProtocolException e) {           
            e.printStackTrace();
        } catch (IOException e) {           
            e.printStackTrace();
        } 
        return s;   
    }


/** return object User */    
public User getObjectById(){
    String url = "mydomain.com.br/[email protected]";;
    String response = HttpClient.get(url);
    Gson gson = new Gson();
    ResponseUser ru = gson.fromJson(response, ResponseUser.class);
    User u = ru.getUser();

    return u;
}


public class ResponseUser {

    @SerializedName("return")
    private User user;

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }       
}

Exception 

11-19 12:56:23.281: E/AndroidRuntime(1481): FATAL EXCEPTION: main
11-19 12:56:23.281: E/AndroidRuntime(1481): Process: br.com.package.myapp, PID: 1481
11-19 12:56:23.281: E/AndroidRuntime(1481): java.lang.RuntimeException: Unable to start activity ComponentInfo{br.com.package.myapp/br.com.package.myapp.act.MainActivity}: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1
11-19 12:56:23.281: E/AndroidRuntime(1481):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at android.os.Handler.dispatchMessage(Handler.java:102)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at android.os.Looper.loop(Looper.java:136)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at android.app.ActivityThread.main(ActivityThread.java:5017)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at java.lang.reflect.Method.invokeNative(Native Method)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at java.lang.reflect.Method.invoke(Method.java:515)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at dalvik.system.NativeStart.main(Native Method)
11-19 12:56:23.281: E/AndroidRuntime(1481): Caused by: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1
11-19 12:56:23.281: E/AndroidRuntime(1481):     at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:176)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at com.google.gson.Gson.fromJson(Gson.java:803)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at com.google.gson.Gson.fromJson(Gson.java:768)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at com.google.gson.Gson.fromJson(Gson.java:717)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at com.google.gson.Gson.fromJson(Gson.java:689)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at br.com.package.myapp.dao.UsuarioDAO.getObjectById(UsuarioDAO.java:46)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at br.com.package.myapp.act.MainActivity.onCreate(MainActivity.java:27)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at android.app.Activity.performCreate(Activity.java:5231)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
11-19 12:56:23.281: E/AndroidRuntime(1481):     ... 11 more
11-19 12:56:23.281: E/AndroidRuntime(1481): Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1
11-19 12:56:23.281: E/AndroidRuntime(1481):     at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:374)
11-19 12:56:23.281: E/AndroidRuntime(1481):     at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:165)
11-19 12:56:23.281: E/AndroidRuntime(1481):     ... 20 more

Upvotes: 1

Views: 2147

Answers (2)

MikO
MikO

Reputation: 18741

First problem is that your User class does not represent the JSON you're getting back from the web service, but it only represents the "return" field inside the response...

Try creating another class that does represent the JSON response, something like:

public class Response {

    @SerializedName("return")
    private User user;

    // getter & setter
}

And then

response = gson.fromJson(response, Response.class);
u = response.getUser();

Apart from that, you have to change the type of the field id in your User class to be a String.
Gson is complaining because you tell it to parse the "ID" into a Long, that's why it says expected BEGIN_OBJECT but was a String, because it finds a String with value "74"

Upvotes: 1

PKP
PKP

Reputation: 194

try {
    JSONObject responseObj = new JSONObject(content);
    Gson gson = new Gson();
    User user = gson.fromJson(responseObj.getJSONObject("return"), User.class);
} catch (JSONException e) {
// catch here               
}

Assuming User class is setup properly

Upvotes: 4

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