JSON - 对象数组中的对象数组

Question

我在解析 JSON 字符串时遇到问题。 JSON 如下：

[
  {
    "firstname": "firstname",
    "lastname": "lastname",
    "address": "address",
    "images": [
      {
        "image": {          
          "url": "url",
          "id": "id"
        }
      },
      {
        "image": {
          "url": "url",
          "id": "id"
        }
      }
    ]
  },
  {
    "firstname": "firstname",
    "lastname": "lastname",
    "address": "address",
    "images": [
      {
        "image": {          
          "url": "url",
          "id": "id"
        }
      },
      {
        "image": {
          "url": "url",
          "id": "id"
        }
      }
    ]
  }
]

我已将所需的 Bean 定义为： Person.java

public class Person implements Serializable {
    private static final long serialVersionUID = 38L;

    private String firstname;
    private String lastname;
    private String address;
    private Image[] images;

    public Person() {

    }

    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 String getAddress() {
        return address;
    }

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

    public Image[] getImages() {
        return images;
    }

    public void setImages(Image[] images) {
        this.images = images;
    }
}

Image.java：

public class Image implements Serializable {
    private static final long serialVersionUID = 39L;

    private String url;
    private String id;

    public Image() {

    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }       
}

现在我将 JSON 字符串解析为：

Gson gson = new Gson(); 
Person[] persons = (Person[])gson.fromJson(jsonString, Person[].class);

现在，如果我打印，

System.out.println(persons[0].getFirstname());
System.out.println(persons[0].getLastname());
System.out.println(persons[0].getAddress());

它将打印相应的值。另外：

persons[0].getImages() is not null;
persons[0].getImages()[0] is not null;

但

persons[0].getImages()[0].getUrl() is null;
persons[0].getImages()[0].getId() is null;

我无法理解我做错了什么？我在定义 bean 时犯了任何错误吗？

我真的很感谢你的帮助。

Answer 1

我假设您不应该指定数组内的对象名称。替换

"image": {          
    "url": "url",
    "id": "id"
}

为简单

{          
    "url": "url",
    "id": "id"
}

如果您想解析指定的 JSON 字符串，您应该具有不同的对象结构：

public class Person implements Serializable {
    private static final long serialVersionUID = 38L;

    private String firstname;
    private String lastname;
    private String address;
    private Foo[] images;
}

public class Foo{
    private Image image;
}
public class Image implements Serializable {
    private static final long serialVersionUID = 39L;

    private String url;
    private String id;
}

Answer 2

我认为您可能希望 JSON 看起来更像

[
  {
    "firstname": "firstname",
    "lastname": "lastname",
    "address": "address",
    "images": [   
      {
          "url": "url",
          "id": "id"
      }...

是这样，它可能会被“image”数组中的“image”标签混淆

Answer 3

您需要另一个对象来包含图像，以便

class Image {
   String image; Info info;
}

class Info {
  String url, String id;
}