如何使用 Json.simple 解析 Java 中的 JSONArray？

Question

I am trying to read a JSON file like this:

{
  "presentationName" : "Here some text",
  "presentationAutor" : "Here some text",
  "presentationSlides" : [
    {
      "title" : "Here some text.",
      "paragraphs" : [
        {
          "value" : "Here some text."
        },
        {
          "value" : "Here some text."
        }
      ]
    },
    {
      "title" : "Here some text.",
      "paragraphs" : [
        {
          "value" : "Here some text.",
          "image" : "Here some text."
        },
        {
          "value" : "Here some text."
        },
        {
          "value" : "Here some text."
        }
      ]
    }
  ]
}

It's for a school exercise. I chose to try and use JSON.simple (from GoogleCode), but I am open to another JSON library. I heard about Jackson and Gson: Are they better than JSON.simple?

Here is my current Java code:

Object obj = parser.parse(new FileReader( "file.json" ));

JSONObject jsonObject = (JSONObject) obj;

// First I take the global data
String name = (String) jsonObject.get("presentationName");
String autor = (String) jsonObject.get("presentationAutor");
System.out.println("Name: "+name);
System.out.println("Autor: "+autor);

// Now we try to take the data from "presentationSlides" array
JSONArray slideContent = (JSONArray) jsonObject.get("presentationSlides");
Iterator i = slideContent.iterator();

while (i.hasNext()) {
    System.out.println(i.next());
    // Here I try to take the title element from my slide but it doesn't work!
    String title = (String) jsonObject.get("title");
    System.out.println(title);
}

I checked out a lot of examples (some on Stack!) but I never found the solution to my problem.

Maybe we can't do this with JSON.simple? What do you recommend?

Answer 1

You never assign a new value to jsonObject , so inside the loop it still refers to the full data object. I think you want something like:

JSONObject slide = i.next();
String title = (String)slide.get("title");

Answer 2

It's working! Thx Russell. I will finish my exercice and try GSON to see the difference.

New code here:

        JSONArray slideContent = (JSONArray) jsonObject.get("presentationSlides");
        Iterator i = slideContent.iterator();

        while (i.hasNext()) {
            JSONObject slide = (JSONObject) i.next();
            String title = (String)slide.get("title");
            System.out.println(title);
        }

Answer 3

For Gson you can paste your json file here : https://www.freecodeformat.com/json2pojo.php Create appropriate pojo classes and then use this code :

Gson gson = new Gson();

    try (Reader reader = new FileReader("pathToYourFile.json")) {

        // Convert JSON File to Java Object
        Root root = gson.fromJson(reader, Root.class);

        // print staff you need
        System.out.println(root.getCommands().get(0).getName());

    } catch (IOException e) {
        e.printStackTrace();
    }