GSON & Volley => 预期为 BEGIN_ARRAY，但在第 1 行第 2 列路径 $ 处为 BEGIN_OBJECT

Question

这个错误让我发疯了，我尝试使用不同类型的 Volley 请求，例如 JsonArrayRequest 和 JsonObjectRequest，但没有运气！！

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: 应为 BEGIN_ARRAY 但在第 1 行第 2 列路径 $ 处为 BEGIN_OBJECT

---

这是 JSON 响应链接 => http://www.mocky.io/v2/58df83a80f00005922eaf4e1

---

这是我的模型类

 public class Order {


@SerializedName("status")
@Expose
private String status; //status

@SerializedName("total")
@Expose
private float price; //total


@SerializedName("created_at")
@Expose
private Date time;

@SerializedName("line_items")
@Expose
public List<ItemsNum> lineItems = new ArrayList<ItemsNum>();

@SerializedName("sub_orders")
@Expose
public List<OrdersNum> subOrders = new ArrayList<OrdersNum>();

@SerializedName("shipping_address")
@Expose
public CusAddress cusAdress;

@SerializedName("customer")
@Expose
public Customer customer;


public Order(Customer customer, String status, float price, String cusPicURL, String firstName, String lastName, Date time, List<ItemsNum> lineItems, List<OrdersNum> subOrders, CusAddress cusAdress) {
    this.status = status;
    this.price = price;
    this.customer = customer;
    this.time = time;
    this.lineItems = lineItems;
    this.subOrders = subOrders;
    this.cusAdress = cusAdress;
}


public Date getTime() {
    return time;
}

public void setTime(Date time) {
    this.time = time;
}

public List<ItemsNum> getLineItems() {
    return lineItems;
}

public void setLineItems(List<ItemsNum> lineItems) {
    this.lineItems = lineItems;
}

public List<OrdersNum> getSubOrders() {
    return subOrders;
}

public void setSubOrders(List<OrdersNum> subOrders) {
    this.subOrders = subOrders;
}



public String getStatus() {
    return status;
}

public void setStatus(String status) {
    this.status = status;
}

public float getPrice() {
    return price;
}

public void setPrice(float price) {
    this.price = price;
}

public CusAddress getCusAdress() {
    return cusAdress;
}

public void setCusAdress(CusAddress cusAdress) {
    this.cusAdress = cusAdress;
}



// //////////// Inner-Classes


public class Customer {

    @SerializedName("avatar_url")
    @Expose
    private String cusPicURL; //avatar_url

    @SerializedName("first_name")
    @Expose
    private String firstName; //first_name

    @SerializedName("last_name")
    @Expose
    private String lastName; //last_name

    public String getCusPicURL() {
        return cusPicURL;
    }

    public void setCusPicURL(String cusPicURL) {
        this.cusPicURL = cusPicURL;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
}

public class CusAddress {

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    @SerializedName("address_1")
    @Expose
    public String address;

    @SerializedName("city")
    @Expose
    public String city;

    @SerializedName("state")
    @Expose
    public String state;

    @SerializedName("country")
    @Expose
    public String country;
}

public class ItemsNum {

    @SerializedName("id")
    @Expose
    public Integer id;
}

public class OrdersNum {

    @SerializedName("id")
    @Expose
    public Integer id;
 }
}

---

我的适配器

  public class OrdersDataAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {


public Context context;
private int num;
ArrayList<Order> orders;


public OrdersDataAdapter(ArrayList<Order> orders, Context context) {
    this.orders = orders;

    this.context = context;
}

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.order_card, parent, false);

    return new NewOrderVH(v);

}


@Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int position) {
    final Order order = this.orders.get(position);
    final NewOrderVH vh1 = (NewOrderVH) holder;
    vh1.setData(orders.get(position));

}

@Override
public int getItemCount() {
    return orders.size();
}


public class NewOrderVH extends RecyclerView.ViewHolder {


    private ImageView cusPic;
    private TextView cusName;
    private TextView CusAdress;
    private TextView vendorsNum;
    private TextView itemsNum;
    private TextView time;


    public NewOrderVH(View itemView) {
        super(itemView);


        orderCard = (CardView) itemView.findViewById(R.id.OrderCard);
        cusPic = (ImageView) itemView.findViewById(R.id.cusPic);
        cusName = (TextView) itemView.findViewById(R.id.cusName);
        CusAdress = (TextView) itemView.findViewById(R.id.CusAdress);
        vendorsNum = (TextView) itemView.findViewById(R.id.vendorsNum);
        itemsNum = (TextView) itemView.findViewById(R.id.itemsNum);
        time = (TextView) itemView.findViewById(R.id.time);


    }

    public void setData(final Order data) {


        cusName.setText(data.customer.getFirstName() + "" + data.customer.getLastName());
        Picasso.with(context).load(data.customer.getCusPicURL()).into(cusPic);
        time.setText(data.getTime().getMinutes());
        vendorsNum.setText(data.getSubOrders().size());
        itemsNum.setText(data.getLineItems().size());
        CusAdress.setText(data.cusAdress.getAddress() + "" + data.cusAdress.getCity() + "" + data.cusAdress.getCountry() + "" + data.cusAdress.getState());

    }


}

}

片段内的请求方法

private void fetchPosts() {


    requestQueue = Volley.newRequestQueue(getActivity());

    StringRequest jRequest = new StringRequest(Request.Method.GET, ENDPOINT, onPostsLoaded, onPostsError);

    requestQueue.add(jRequest);

}


private final Response.Listener<String> onPostsLoaded = new Response.Listener<String>() {
    @Override
    public void onResponse(String response) {

        Gson gson = new Gson();
        Type listType = new TypeToken<List<Order>>() {}.getType();
        modelData = gson.fromJson(response, listType);


        adapter = new OrdersDataAdapter((ArrayList<Order>) modelData, getActivity());
        recyclerView.setAdapter(adapter);
        adapter.setMode(Attributes.Mode.Single);

    }
};

private final Response.ErrorListener onPostsError = new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {
        Log.e("PostActivity", error.toString());
    }
};

Answer 1

你的问题是orders 对象。您不会反序列化 orders。你可以解决这个问题

public class OrderHolder{
    private List<Order> orders;

    public List<Order> getOrders(){ return orders; }

} 

OrderHolder holder = new Gson().fromJson(response, OrderHolder.class);
modelData = holder.getOrders();

或

JsonElement jelement = new JsonParser().parse(response);
JsonObject  jobject = jelement.getAsJsonObject();
String ordersString = jobject.get("orders").getAsString();

Gson gson = new Gson();
Type listType = new TypeToken<List<Order>>() {}.getType();
modelData = gson.fromJson(ordersString, listType);

Answer 2

预期为 BEGIN_ARRAY，但在第 1 行第 2 列路径 $ 处为 BEGIN_OBJECT

这很容易阅读：这意味着您正在解析类似列表的内容（因此需要 BEGIN_ARRAY [），但给定的 JSON 文档以 BEGIN_OBJECT { 开头，这是由于通过不匹配的预期类型。它发生在 JSON 文档的开头。

除了mismanc的answer之外，还有第三种方式，需要稍微多一点的代码（虽然可以提取到一个方法中），但它不需要包装器或中间JSON树像JsonElement 及其子类（第一种情况可能会消耗更多内存，而第二种情况肯定会消耗更多内存，因为整个中间 JSON 树必须存储在内存中）。

// JsonReader allows to read JSON token stream
try ( final JsonReader jsonReader = new JsonReader(new StringReader(JSON)) ) {
    // Just skip the leading `{`
    jsonReader.beginObject();
    // Check if the next property name is what we're expecting
    final String name = jsonReader.nextName();
    if ( !name.equals("orders") ) {
        throw new MalformedJsonException("Unexpected: " + name);
    }
    // If it's fine, then we:
    // * are assuming the JsonReader "pointer" is at the property value now
    // * are asking Gson for the proper type adapter
    @SuppressWarnings("unchecked")
    final TypeAdapter<List<Order>> typeAdapter = (TypeAdapter<List<Order>>) gson.getAdapter(TypeToken.get(orderListType));
    // Just read the orders
    final List<Order> orders = typeAdapter.read(jsonReader);
    System.out.println(orders);
}

到 POJO 自动转换器/生成器的 JSON 模式并不总是创建最佳映射。例如：

• ItemsNum 和 OrdersNum 都由相同的 POJO 结构表示，但也可以是 final class Id { @SerializedName("id") final Integer id = null; }。
• 客户avatar_url表示为java.lang.String，但也可以是java.net.URL。

小笔记：

• Gson 不需要在每次需要反序列化时创建类实例。它们是完全线程安全的，可以实例化一次，然后轻松地重复使用。此外，创建和配置 else Gson 实例可以注入到您的代码中。
• 使用TypeTokens 生成的Type 实例可以被视为不可变值对象，因此也可以缓存到static final 字段中。

Answer 3

这是正确的答案，我使用了错误的请求类型..！

  JsonObjectRequest jsObjRequest = new     
  JsonObjectRequest(Request.Method.GET,ENDPOINT,null,
            new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {

                    Gson gson = new Gson();
                    Type listType = new TypeToken<List<Order>>() {}.getType();
                    try {

                        List<Order> o = new ArrayList<>();
                        o = gson.fromJson(response.getJSONArray("orders").toString(), listType);
                        if(o != null && !o.isEmpty()){

                            modelData.addAll(o);
                            adapter.notifyDataSetChanged();
                        }

                    } catch (JSONException e) {
                        e.printStackTrace();
                    }

                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {

                }
            });

    requestQueue.add(jsObjRequest);

}