我有一个 JSON 文件，其中包含一些数组。我想遍历文件数组并获取它们的元素和值。

这是我的文件的样子:

{
"JObjects": {
    "JArray1": [
        {
            "A": "a",
            "B": "b",
            "C": "c"
        },
        {
            "A": "a1",
            "B": "b2",
            "C": "c3",
            "D": "d4"
            "E": "e5"
        },
        {
            "A": "aa",
            "B": "bb",
            "C": "cc",
            "D": "dd"
        }

    ]
}

}       

这是我已经走了多远:

JSONObject object = new JSONObject("json-file.json");
JSONObject getObject = object.getJSONObject("JObjects");
JSONArray getArray = getObject.getJSONArray("JArray1");

for(int i = 0; i < getArray.length(); i++)
{
      JSONObject objects = getArray.getJSONArray(i);
      //Iterate through the elements of the array i.
      //Get thier value.
      //Get the value for the first element and the value for the last element.
}

有可能做这样的事情吗？

我之所以要这样做是因为文件中的数组具有不同数量的元素。

最佳答案

改变

JSONObject objects = getArray.getJSONArray(i);

到

JSONObject objects = getArray.getJSONObject(i);

或到

JSONObject objects = getArray.optJSONObject(i);

取决于您使用的 JSON-to/from-Java 库。 (看起来 getJSONObject 对你有用。)

然后，访问“对象”中的字符串元素JSONObject ，按元素名称取出它们。

String a = objects.get("A");

如果您需要 JSONObject 中的元素名称，可以使用静态实用方法JSONObject.getNames(JSONObject)这样做。

String[] elementNames = JSONObject.getNames(objects);

"Get the value for the first element and the value for the last element."

如果“元素”指的是数组中的组件，请注意第一个组件在索引 0 处，最后一个组件在索引 getArray.length() - 1 处.

I want to iterate though the objects in the array and get thier component and thier value. In my example the first object has 3 components, the scond has 5 and the third has 4 components. I want iterate though each of them and get thier component name and value.

下面的代码正是这样做的。

import org.json.JSONArray;
import org.json.JSONObject;

public class Foo
{
  public static void main(String[] args) throws Exception
  {
    String jsonInput = "{\"JObjects\":{\"JArray1\":[{\"A\":\"a\",\"B\":\"b\",\"C\":\"c\"},{\"A\":\"a1\",\"B\":\"b2\",\"C\":\"c3\",\"D\":\"d4\",\"E\":\"e5\"},{\"A\":\"aa\",\"B\":\"bb\",\"C\":\"cc\",\"D\":\"dd\"}]}}";

    // "I want to iterate though the objects in the array..."
    JSONObject outerObject = new JSONObject(jsonInput);
    JSONObject innerObject = outerObject.getJSONObject("JObjects");
    JSONArray jsonArray = innerObject.getJSONArray("JArray1");
    for (int i = 0, size = jsonArray.length(); i < size; i++)
    {
      JSONObject objectInArray = jsonArray.getJSONObject(i);

      // "...and get thier component and thier value."
      String[] elementNames = JSONObject.getNames(objectInArray);
      System.out.printf("%d ELEMENTS IN CURRENT OBJECT:\n", elementNames.length);
      for (String elementName : elementNames)
      {
        String value = objectInArray.getString(elementName);
        System.out.printf("name=%s, value=%s\n", elementName, value);
      }
      System.out.println();
    }
  }
}
/*
OUTPUT:
3 ELEMENTS IN CURRENT OBJECT:
name=A, value=a
name=B, value=b
name=C, value=c

5 ELEMENTS IN CURRENT OBJECT:
name=D, value=d4
name=E, value=e5
name=A, value=a1
name=B, value=b2
name=C, value=c3

4 ELEMENTS IN CURRENT OBJECT:
name=D, value=dd
name=A, value=aa
name=B, value=bb
name=C, value=cc
*/

https://stackoverflow.com/questions/6697147/