com.google.gson.JsonSyntaxException：java.lang.IllegalStateException：预期为 BEGIN_ARRAY，但在第 1 行第 1 列处为 STRING

Question

GsonBuilder builder = new GsonBuilder();
Gson mGson = builder.create();
spinnerData = Arrays.asList(mGson.fromJson(response, Item.class));

After executing this code, size of spinnerdata list is showing 0. my response is:

{"result":[{"item_code":"r2010","item_name":"rice"},{"item_code":"w2010","item_name":"wheat"},{"item_code":"p2010","item_name":"paddy"},{"item_code":"b2010","item_name":"bran"}]}

my code for item.java is:

package com.example.booking;

import com.google.gson.annotations.SerializedName;
public class Item {
     @SerializedName("item_code")
     private String item_code;
     @SerializedName("item_name")
     private String item_name;

    public Item() {
    }

    public Item(String item_code, String item_name) {
        this.item_code = item_code;
        this.item_name = item_name;
    }

    public void setCode(String item_code) {
        this.item_code = item_code;
    }

    public void setName(String item_name) {
        this.item_name = item_name;
    }

    public String getCode() {
        return this.item_code;
    }

    public String getName() {
        return this.item_name;
    }
}

the error shows:

E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.booking, PID: 12452 com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1 at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:176) at com.google.gson.Gson.fromJson(Gson.java:803) at com.google.gson.Gson.fromJson(Gson.java:768) at com.google.gson.Gson.fromJson(Gson.java:717) at com.google.gson.Gson.fromJson(Gson.java:689) at com.example.booking.MainActivity$2.onResponse(MainActivity.java:82) at com.example.booking.MainActivity$2.onResponse(MainActivity.java:77) at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:60) at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:30) at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatch Message(Handler.java:95) at android.os.Looper.loop(Looper.java:179) at android.app.ActivityThread.main(ActivityThread.java:5730) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:681) Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1 at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:374) at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:165) at com.google.gson.Gson.fromJson(Gson.java:803) at com.google.gson.Gson.fromJson(Gson.java:768) at com.google.gson.Gson.fromJson(Gson.java:717) at com.google.gson.Gson.fromJson(Gson.java:689) at com.example.booking.MainActivity$2.onResponse(MainActivity.java:82) at com.example.booking.MainActivity$2.onResponse(MainActivity.java:77) at com.android.volley.toolbox.StringRequest.delive rResponse(StringRequest.java:60) at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:30) at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:179) at android.app.ActivityThread.main(ActivityThread.java:5730) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:681)

after appyling the changes

Answer 1

Please check your response carefully. Here, result is an object, not an array. There is an array inside the result object. So you need to parse the JSON into an object. Then you can get an array from the result . I have given a sample entity from your given response and the output-

You can use your given code but with a little change -

String response = "{\"result\":[{\"item_code\":\"r2010\",\"item_name\":\"rice\"}," +
                "{\"item_code\":\"w2010\",\"item_name\":\"wheat\"},{\"item_code\":\"p2010\"," +
                "\"item_name\":\"paddy\"},{\"item_code\":\"b2010\",\"item_name\":\"bran\"}]}";

        GsonBuilder builder = new GsonBuilder();
        Gson mGson = builder.create();
        Item spinnerData = mGson.fromJson(response, Item.class);

        List<Result> list = spinnerData.getResult();

Here, list will be your actual result.

Your Entity Is not correct for your response. The code below is the actual entity of your given response JSON -

public class Item {
    @SerializedName("result")
    private List<Result> result;

    public List<Result> getResult() { return result; }

    public void setResult(List<Result> result) { this.result = result; }
}

class Result {
    @SerializedName("item_code")
    private String itemCode;

    @SerializedName("item_name")
    private String itemName;

    public void setItemCode(String itemCode){ this.itemCode = itemCode; }

    public String getItemCode(){ return itemCode; }

    public void setItemName(String itemName){ this.itemName = itemName; }

    public String getItemName(){ return itemName; }
}

Answer 2

Another solution to get hide of objects that the only attribute is a list without rewriting model classes (if not necessary)

import com.google.gson.reflect.TypeToken;


spinnerData = mGson.fromJson(new JSONObject(response).getJSONArray("result").toString(), new TypeToken<Item>(){}.getType());