如何使用Java和Gson从Json获取对象列表

Question

I try to read from a Json file and convet it to Java object, I have the following Java code to read the Json:

class Item {
    String name;
    int itemId;
    Date AddTime;
    String group;
}

Gson gson = new Gson();
gson.fromJson(jsonFile, new TypeToken<Map<String, ArrayList<Item>>>() {}.getType());

And the Json file contains the following data:

{
  "item1": [{
    "name": "test1",
    "itemId": "1",
    "AddTime": "2018-09-05T10:35:56.015Z",
    "group": "computer"
  }, {
    "name": "test2",
    "itemId": "2",
    "AddTime": "2018-09-05T10:35:56.016Z",
    "group": "computer"
  }, {
    "name": "test3",
    "itemId": "3",
    "AddTime": "2018-09-05T10:35:56.017Z",
    "group": "computer"
  }],
  "item2": [{
    "name": "test4",
    "itemId": "4",
    "AddTime": "2018-09-05T10:35:56.015Z",
    "group": "computer"
  }, {
    "name": "test5",
    "itemId": "5",
    "AddTime": "2018-09-05T10:35:56.016Z",
    "group": "computer"
  }, {
    "name": "test6",
    "itemId": "6",
    "AddTime": "2018-09-05T10:35:56.017Z",
    "group": "computer"
  }]
}

I got the following:

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1

I am new to Java, what is the problem and how to fix it?

Answer 1

I'm not sure if this is what you need, but I think the solution could be something like this.

According with your dataset. Inside of each one of your items you have an arrayList with tests (test1, test2...) so you will need something like this:

    class Item {
       ArrayList<Test> tests;
    }

    class Test{
       String name;
       int itemId;
       Date AddTime;
       String group;
    }