Android GSON Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2

Question

I am trying to parse the following JSON :

{
  "Message": "The request is invalid.",
  "ModelState": {
    "": [
      "Name [email protected] is already taken.",
      "Email '[email protected]' is already taken."
    ]
  }
}

The code i used :

ErrorRequest page = gson.fromJson(response.getResponseString(), ErrorRequest.class);

But i am getting the error: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2

My POJO classes are : ErrorRequest.Java

package com.devinedesign.cleanride.domain;

import com.google.gson.annotations.SerializedName;

import java.util.ArrayList;
import java.util.List;

public class ErrorRequest
{
    @SerializedName("Message")
    private String message;

    @SerializedName("ModelState")
    private List<ModelState> modelState;

    public ErrorRequest(String message,List<ModelState> modelState)
    {
        this.message    = message;
        this.modelState = modelState;
    }

    public String getMessage()
    {
        return message;
    }

    public void setMessage(String message)
    {
        this.message = message;
    }

    public List<ModelState> getModelState()
    {
        return modelState;
    }

    public void setModelState(List<ModelState> modelState)
    {
        this.modelState = modelState;
    }
}

ModelState.Java

package com.devinedesign.cleanride.domain;

import com.google.gson.annotations.SerializedName;


public class ModelState
{
    @SerializedName("ModelState")
    private String modelState;

    public ModelState(String modelState)
    {
        this.modelState = modelState;
    }

    public String getModelState() {
        return modelState;
    }

    public void setModelState(String modelState) {
        this.modelState = modelState;
    }
}

Is your JSON supposed to have an empty key string in front of the array? — OneCricketeer
– OneCricketeer, Commented Mar 24, 2016 at 13:35
Well my client provided me with that in their API. Is that the reason why i was getting the error? — aaa111
– aaa111, Commented Mar 24, 2016 at 13:37
It should probably look more like { "Message": "The request is invalid.", "ModelState": [ "Name [email protected] is already taken.", "Email '[email protected]' is already taken." ] } . The empty key just seems to abstract a pretty simple json response. — zgc7009
– zgc7009, Commented Mar 24, 2016 at 13:39
That isn't the reason for that specific error, but I'm guessing it will cause an error after you fix the first one — OneCricketeer
– OneCricketeer, Commented Mar 24, 2016 at 13:44

OneCricketeer · Accepted Answer · 2016-03-24 13:42:31Z

2

ModelState here is an object.

"ModelState": {

Yet, you declared it as a List, so Gson is trying to parse an array.

@SerializedName("ModelState")
private List<ModelState> modelState;

You can fix that with

@SerializedName("ModelState")
private ModelState modelState;

But, then you should be careful about how this is will parsed.. This will be an object with a List<String>, but that empty key should have a value in it. Unless maybe you can do @SerializedName(""), but I'm not sure.

{
    "": [
      "Name [email protected] is already taken.",
      "Email '[email protected]' is already taken."
    ]
}

answered Mar 24, 2016 at 13:42

OneCricketeer

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Comments

aaa111 · Accepted Answer · 2016-03-30 11:45:56Z

Ok i finally fixed my issue, and my client updated the JSON with following format

{"Message":"The request is invalid.","ModelState":{"Errors":["Name [email protected] is already taken.","Email '[email protected]' is already taken."]}}

And after that i modified my POJO's in the following way:

ErrorRequest.Java

package com.devinedesign.cleanride.domain;

import com.google.gson.annotations.SerializedName;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

public class ErrorRequest
{
@SerializedName("Message")
private String message;

@SerializedName("ModelState")
private ModelState modelState;

public ErrorRequest(String message,ModelState modelState)
{
    this.message    = message;
    this.modelState = modelState;
}

public String getMessage()
{
    return message;
}

public void setMessage(String message)
{
    this.message = message;
}

public ModelState getModelState()
{
    return modelState;
}

public void setModelState(ModelState modelState)
{
    this.modelState = modelState;
}
}

ModelState.java

package com.devinedesign.cleanride.domain;

import com.google.gson.annotations.SerializedName;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;


public class ModelState
{
@SerializedName("Errors")
private List<String> errors;

public ModelState(ArrayList<String> errors)
{
    this.errors = errors;
}

public List<String> getErrors() {
    return errors;
}

public void setErrors(List<String> errors) {
    this.errors = errors;
}
}

Now everything works perfectly.

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