Question

我想用以下JSON创建一个对象Checklist。但我认为没有创建Arraylist类别。我没有异常调试控制台在创建对象时进入bucle：“背景部分并发标记扫描GC释放165848（5MB）AllocSpace对象，144（1852KB）LOS对象，22％免费，55MB / 71MB，暂停5.343ms总共67.660ms“

{"type_check":"CAB","description":"simple cabin","categories":[{"category_id":"3","description":"Confort"},{"category_id":"4","description":"Servicios"},{"category_id":"5","description":"Alimentación"},{"category_id":"6","description":"Personal"},{"category_id":"7","description":"Instalaciones"}]}

以下课程：

Checklist.class

public class Checklist {

private String type_check;
private String description;
private ArrayList<Category> categories;}

Category.class

public class Category {


private int category_id;
private String description;

}

创建对象：

 Gson gson = new GsonBuilder().create();
                            Checklist check = gson.fromJson(checklist.toString(), Checklist.class);

我解析json时必须指定arraylist吗？感谢，并有一个愉快的一天。

Answer 1

以下代码

是json的样子

[
  {
"type_check": "CAB_0",
"description": "simple cabin",
"categories": [
  {
    "category_id": 0,
    "description": "Description_0"
  },
  {
    "category_id": 1,
    "description": "Description_1"
  },
  {
    "category_id": 2,
    "description": "Description_2"
  },
  {
    "category_id": 3,
    "description": "Description_3"
  },
  {
    "category_id": 4,
    "description": "Description_4"
  },
  {
    "category_id": 5,
    "description": "Description_5"
  },
  {
    "category_id": 6,
    "description": "Description_6"
  }
]

}， { ＆＃34; type_check＆＃34;：＆＃34; CAB_1＆＃34;，＆＃34;描述＆＃34;：＆＃34;简单的小屋＆＃34;，＆＃34;类别＆＃34;：[ { ＆＃34; category_id＆＃34;：0，＆＃34;描述＆＃34;：＆＃34; Description_0＆＃34; }， { ＆＃34; category_id＆＃34;：1，＆＃34;描述＆＃34;：＆＃34; Description_1＆＃34; }， { ＆＃34; category_id＆＃34;：2，＆＃34;描述＆＃34;：＆＃34; Description_2＆＃34; }， { ＆＃34; category_id＆＃34;：3，＆＃34;描述＆＃34;：＆＃34; Description_3＆＃34; }， { ＆＃34; category_id＆＃34;：4，＆＃34;描述＆＃34;：＆＃34; Description_4＆＃34; }， { ＆＃34; category_id＆＃34;：5，＆＃34;描述＆＃34;：＆＃34; Description_5＆＃34; }， { ＆＃34; category_id＆＃34;：6，＆＃34;描述＆＃34;：＆＃34; Description_6＆＃34; } ] }， { ＆＃34; type_check＆＃34;：＆＃34; CAB_2＆＃34;，＆＃34;描述＆＃34;：＆＃34;简单的小屋＆＃34;，＆＃34;类别＆＃34;：[ { ＆＃34; category_id＆＃34;：0，＆＃34;描述＆＃34;：＆＃34; Description_0＆＃34; }， { ＆＃34; category_id＆＃34;：1，＆＃34;描述＆＃34;：＆＃34; Description_1＆＃34; }， { ＆＃34; category_id＆＃34;：2，＆＃34;描述＆＃34;：＆＃34; Description_2＆＃34; }， { ＆＃34; category_id＆＃34;：3，＆＃34;描述＆＃34;：＆＃34; Description_3＆＃34; }， { ＆＃34; category_id＆＃34;：4，＆＃34;描述＆＃34;：＆＃34; Description_4＆＃34; }， { ＆＃34; category_id＆＃34;：5，＆＃34;描述＆＃34;：＆＃34; Description_5＆＃34; }， { ＆＃34; category_id＆＃34;：6，＆＃34;描述＆＃34;：＆＃34; Description_6＆＃34; } ] }， { ＆＃34; type_check＆＃34;：＆＃34; CAB_3＆＃34;，＆＃34;描述＆＃34;：＆＃34;简单的小屋＆＃34;，＆＃34;类别＆＃34;：[ { ＆＃34; category_id＆＃34;：0，＆＃34;描述＆＃34;：＆＃34; Description_0＆＃34; }， { ＆＃34; category_id＆＃34;：1，＆＃34;描述＆＃34;：＆＃34; Description_1＆＃34; }， { ＆＃34; category_id＆＃34;：2，＆＃34;描述＆＃34;：＆＃34; Description_2＆＃34; }， { ＆＃34; category_id＆＃34;：3，＆＃34;描述＆＃34;：＆＃34; Description_3＆＃34; }， { ＆＃34; category_id＆＃34;：4，＆＃34;描述＆＃34;：＆＃34; Description_4＆＃34; }， { ＆＃34; category_id＆＃34;：5，＆＃34;描述＆＃34;：＆＃34; Description_5＆＃34; }， { ＆＃34; category_id＆＃34;：6，＆＃34;描述＆＃34;：＆＃34; Description_6＆＃34; } ] }， { ＆＃34; type_check＆＃34;：＆＃34; CAB_4＆＃34;，＆＃34;描述＆＃34;：＆＃34;简单的小屋＆＃34;，＆＃34;类别＆＃34;：[ { ＆＃34; category_id＆＃34;：0，＆＃34;描述＆＃34;：＆＃34; Description_0＆＃34; }， { ＆＃34; category_id＆＃34;：1，＆＃34;描述＆＃34;：＆＃34; Description_1＆＃34; }， { ＆＃34; category_id＆＃34;：2，＆＃34;描述＆＃34;：＆＃34; Description_2＆＃34; }， { ＆＃34; category_id＆＃34;：3，＆＃34;描述＆＃34;：＆＃34; Description_3＆＃34; }， { ＆＃34; category_id＆＃34;：4，＆＃34;描述＆＃34;：＆＃34; Description_4＆＃34; }， { ＆＃34; category_id＆＃34;：5，＆＃34;描述＆＃34;：＆＃34; Description_5＆＃34; }， { ＆＃34; category_id＆＃34;：6，＆＃34;描述＆＃34;：＆＃34; Description_6＆＃34; } ] }， { ＆＃34; type_check＆＃34;：＆＃34; CAB_5＆＃34;，＆＃34;描述＆＃34;：＆＃34;简单的小屋＆＃34;，＆＃34;类别＆＃34;：[ { ＆＃34; category_id＆＃34;：0，＆＃34;描述＆＃34;：＆＃34; Description_0＆＃34; }， { ＆＃34; category_id＆＃34;：1，＆＃34;描述＆＃34;：＆＃34; Description_1＆＃34; }， { ＆＃34; category_id＆＃34;：2，＆＃34;描述＆＃34;：＆＃34; Description_2＆＃34; }， { ＆＃34; category_id＆＃34;：3，＆＃34;描述＆＃34;：＆＃34; Description_3＆＃34; }， { ＆＃34; category_id＆＃34;：4，＆＃34;描述＆＃34;：＆＃34; Description_4＆＃34; }， { ＆＃34; category_id＆＃34;：5，＆＃34;描述＆＃34;：＆＃34; Description_5＆＃34; }， { ＆＃34; category_id＆＃34;：6，＆＃34;描述＆＃34;：＆＃34; Description_6＆＃34; } ] }， { ＆＃34; type_check＆＃34;：＆＃34; CAB_6＆＃34;，＆＃34;描述＆＃34;：＆＃34;简单的小屋＆＃34;，＆＃34;类别＆＃34;：[ { ＆＃34; category_id＆＃34;：0，＆＃34;描述＆＃34;：＆＃34; Description_0＆＃34; }， { ＆＃34; category_id＆＃34;：1，＆＃34;描述＆＃34;：＆＃34; Description_1＆＃34; }， { ＆＃34; category_id＆＃34;：2，＆＃34;描述＆＃34;：＆＃34; Description_2＆＃34; }， { ＆＃34; category_id＆＃34;：3，＆＃34;描述＆＃34;：＆＃34; Description_3＆＃34; }， { ＆＃34; category_id＆＃34;：4，＆＃34;描述＆＃34;：＆＃34; Description_4＆＃34; }， { ＆＃34; category_id＆＃34;：5，＆＃34;描述＆＃34;：＆＃34; Description_5＆＃34; }， { ＆＃34; category_id＆＃34;：6，＆＃34;描述＆＃34;：＆＃34; Description_6＆＃34; } ] } ]

Checklist.Java代码在这里

public class Checklist {

private String type_check;
private String description;
private ArrayList<Category> categories;

public String getType_check() {
    return type_check;
}

public void setType_check(String type_check) {
    this.type_check = type_check;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public ArrayList<Category> getCategories() {
    return categories;
}

public void setCategories(ArrayList<Category> categories) {
    this.categories = categories;
}

}

Category.java代码在这里

public class Category {

private int category_id;
private String description;

public int getCategory_id() {
    return category_id;
}
public void setCategory_id(int category_id) {
    this.category_id = category_id;
}
public String getDescription() {
    return description;
}
public void setDescription(String description) {
    this.description = description;
}


}

TestCode.Java代码在这里

import java.util.ArrayList;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

public class TestCode {

public static void main(String[] args) {
    ArrayList<Checklist> list = new ArrayList<Checklist>();

    list = createList();

    String stringJson = (new Gson()).toJson(list);

    System.out.println("##### JSON from a object #######");

    System.out.println(stringJson);

    System.out.println("###### Convert JSON to object ######");

    ArrayList<Checklist> list2 = new ArrayList<Checklist>();

    list2 = (new Gson()).fromJson(stringJson,
            new TypeToken<ArrayList<Checklist>>() {
            }.getType());

    System.out.println("####### print out put ######");

    for (int i = 0; i < list2.size(); i++) {
        Checklist checklist = list2.get(i);
        System.out.println(checklist.getType_check() + "");
        System.out.println(checklist.getDescription() + "");

        ArrayList<Category> categorys = checklist.getCategories();

        for (int j = 0; j < categorys.size(); j++) {
            Category category = categorys.get(j);
            System.out.println(category.getCategory_id() + "");
            System.out.println(category.getDescription() + "");
        }

    }

}

private static ArrayList<Checklist> createList() {
    // TODO Auto-generated method stub
    ArrayList<Checklist> list = new ArrayList<Checklist>();

    for (int i = 0; i < 7; i++) {
        Checklist checklist = new Checklist();
        checklist.setType_check("CAB_" + i);
        checklist.setDescription("simple cabin");

        ArrayList<Category> categorys = new ArrayList<Category>();

        for (int j = 0; j < 7; j++) {
            Category category = new Category();
            category.setCategory_id(j);
            category.setDescription("Description_" + j);
            categorys.add(category);
        }
        checklist.setCategories(categorys);
        list.add(checklist);
    }

    return list;
}

}

带有gson的json到java对象（与arraylist嵌套的对象）

1 个答案: