Question

我有以下课程：

public class MyProperty
{
   public String Key;
   public String Value;
}

public class MyModel
{
   public String Name;
   public List<MyProperty> Properties;
}

当我尝试像这样序列化MyObject类型的对象时：

MyModel m = new MyModel(){{
   Name="aaaa";
   Properties = new ArrayList<MyProperty>();
}};

m.Properties = new ArrayList<MyProperty>();

m.Properties.add(new MyProperty() {{ Key="a"; Value="1"; }});
m.Properties.add(new MyProperty() {{ Key="b"; Value="11"; }});
m.Properties.add(new MyProperty() {{ Key="c"; Value="111"; }});

String json1 = g.toJson(m, MyModel.class);

我得到以下结果：

{"Name":"aaaa","Properties":[null,null,null]}

为什么当源对象肯定不为空时，属性列表被序列化为null列表？

字符串的反序列化

{"Name":"aaaa","Properties":[{"Key":"a","Value":"1" etc }]}

工作正常。

Answer 1

您可能遇到的问题是多态性 - 您的模型表明属性属于＆＃34; MyProperty＆＃34;但是你的代码片段使用＆＃34; SyncProperty＆＃34;。与Gson有关的一些问题 - 看看这里的讨论：How to handle deserializing with polymorphism?

Answer 2

我会告诉您为什么code有您要查找的输出而不是您所问的code。

代码

import java.util.ArrayList;

import com.google.gson.Gson;

public class TestOneDrive {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        MyModel model = new MyModel();
        model.setName("someName");

        ArrayList<MyProperty> myProperties = new ArrayList<>();

        for (int i = 0; i < 5; i++) {
            MyProperty myProperty = new MyProperty();
            myProperty.setKey("Key_" + i);
            myProperty.setValue("Value_" + i);
            myProperties.add(myProperty);
        }
        model.setProperties(myProperties);

        String result = (new Gson()).toJson(model);
        System.out.println("" + result);

    }

}

class MyProperty {

    public String Key;
    public String Value;

    public String getKey() {
        return Key;
    }

    public void setKey(String key) {
        Key = key;
    }

    public String getValue() {
        return Value;
    }

    public void setValue(String value) {
        Value = value;
    }
}

class MyModel {
    public String Name;
    public ArrayList<MyProperty> Properties;

    public String getName() {
        return Name;
    }

    public void setName(String name) {
        Name = name;
    }

    public ArrayList<MyProperty> getProperties() {
        return Properties;
    }

    public void setProperties(ArrayList<MyProperty> properties) {
        Properties = properties;
    }
}

输出

{
  "Name": "someName",
  "Properties": [
    {
      "Key": "Key_0",
      "Value": "Value_0"
    },
    {
      "Key": "Key_1",
      "Value": "Value_1"
    },
    {
      "Key": "Key_2",
      "Value": "Value_2"
    },
    {
      "Key": "Key_3",
      "Value": "Value_3"
    },
    {
      "Key": "Key_4",
      "Value": "Value_4"
    }
  ]
}

Android java / gson序列化List <myobject>生成null，null，null

2 个答案: