java - 将 Json 文件读取到 ArrayList

Question

我有一个任务要创建一些类似于测验的东西。老师给了我们Questions的所有接口(interface)和 Test甚至“图形层”为 display the quiz .

我为测试和问题接口(interface)创建了两个类。测试类具有 Questions 对象的 listArray 以及其他属性。 Question 类具有您可以在 JSON 文件中看到的属性(标题、分数、标记等)。

为了读取 Json 文件，我创建了方法“loadfromJsonFile”，它完美地打印了该文件，但我无法弄清楚如何将文件中的每个问题对象关联到 arrayList。

Json 文件:

[
{
    "type": "MultipleChoice",
    "question": {
        "title": "Question 1",
        "score": 4,
        "mark":  5,
        "question_description": "The ability of an object to take on many forms is:",
        "options": [
            "Polymorphism",
            "Encapsulation",
            "Design Patter",
            "Does not Exist"
        ],
        "correct_answer": "Polymorphism"
    }
},

{
    "type": "MultipleChoice",
    "question": {
        "title": "Question 2",
        "score": 4,
        "mark":  5,
        "question_description": "The bundling of data with the methods that operate on that data is:",
        "options": [
            "Polymorphism",
            "Encapsulation",
            "Design Patter",
            "Does not Exist"
        ],
        "correct_answer": "Encapsulation"
    }
},
{
    "type": "YesNo",
    "question": {
        "title": "Question 3",
        "score": 4,
        "mark":  5,
        "question_description": "Object Oriented Programming is exclusive to the JAVA programming language",
        "correct_answer": "no"
    }
},
{
    "type": "Numeric",
    "question": {
        "title": "Question 4",
        "score": 4,
        "mark":  5,
        "question_description": "How many programming languages are taught in Paradigmas de Programação?",
        "correct_answer": "1"
    }
}]

读取Json文件的代码:

public boolean loadFromJSONFile(String s) throws TestException {
    String path = "teste_A.json";
    BufferedReader reader = null;

    try{
        reader = new BufferedReader(new FileReader(path));

        JsonStreamParser p = new JsonStreamParser(reader);
        JsonArray arr = (JsonArray) p.next();

        for(int i=0;i<arr.size();i++){
            System.out.println("--------------------------------------Question"+i+"--------------------------------------------");
            JsonElement arrayElement = arr.get(i);
            JsonObject obj = arrayElement.getAsJsonObject();
            String type=obj.get("type").getAsString();
            System.out.println("Type: " + type);
            JsonObject list =obj.get("question").getAsJsonObject();
            String title=list.get("title").getAsString();
            System.out.println("Title: " + title);
            int score=list.get("score").getAsInt();
            System.out.println("Score: " + score);
            int mark=list.get("mark").getAsInt();
            System.out.println("Mark: " + mark);
            String Description=list.get("question_description").getAsString();
            System.out.println("Description: " + Description);
            JsonArray opt = list.getAsJsonArray("options");
            if(opt!=null){
                System.out.println("Options: \n");
                for (int j = 0; j < opt.size(); j++) {
                    JsonPrimitive value = opt.get(j).getAsJsonPrimitive();
                    System.out.print("      Option"+ (j+1) +": "+ value.getAsString()+ " \n");
                }
                System.out.println("\n");
            }

            String CorrectAnswer = list.get("correct_answer").getAsString();
            System.out.println("Correct: " + CorrectAnswer);
        }

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } finally {
        try {
            reader.close();
        }catch (IOException ex){
            ex.printStackTrace();
        }
    }


    return false;
}

Answer 1

这是我的理解:你可以读取json文件并解析内容就好，但问题是如何将结果传递回调用者而不返回参数本身。从代码片段来看，该行 this.current_question = this.test.getQuestion(this.question_number);看起来像这个 ArrayList 将在程序中查询。

据此，我想象了几种可能性:

1) 有一个setQuestion(<params>)您可以在老师提供的代码中调用该方法。

2) 有一个变量如this.test或this.questions你应该设置的。

无论哪种情况，您都可以将每个问题添加到 for 中环形。例如，

for(int i=0;i<arr.size();i++){
            System.out.println("--------------------------------------Question"+i+"--------------------------------------------");
            JsonElement arrayElement = arr.get(i);
            JsonObject obj = arrayElement.getAsJsonObject();
            //add obj via variable assignment
            this.test.Add(obj);
            //or, add obj via set method
            this.test.setQuestion(i, obj); //or whatever parameters are needed :)

编辑:

由于您的 Question 类扩展了 IQuestion，因此您可以将 Question 类的实例强制转换为 IQuestion。另外，Question 类使用 Gson 库为您进行反序列化，这意味着您节省了一些跑腿工作。 (耶!)

for(int i=0;i<arr.size();i++){
            //get the whole json array element
            JsonElement arrayElement = arr.get(i);
            //...
            //get question object
            JsonObject list = obj.get("question").getAsJsonObject();
            //cast to IQuestion using the Question class Gson deserializer
            IQuestion q = new Gson().fromJson(list, Question.class);
            //And, add using built in method
            this.test.setQuestion(q);

This website有一些Gson反序列化的例子，上面我用过其中一个。

编辑:

向 Question 类添加构造函数后，添加特定类型问题的代码将需要类型转换。

for(int i=0;i<arr.size();i++){
            //get the whole json array element
            JsonElement arrayElement = arr.get(i);
            //...
            //get question object
            JsonObject list = obj.get("question").getAsJsonObject();
            //cast question to correct interface based on question type
            if (type=="Multiple Choice") {
               IQuestionMultipleChoice questionMP = (IQuestionMultipleChoice) new Question(<params>);
               this.test.setQuestion(questionMP);
            } else if(type=="Yes/No") {
               //...