Java中JSON字符串与java对象的互换实例详解

转自：https://blog.csdn.net/aa23252658787/article/details/53380403

在前端：
1.如果json是List对象转换的，可以直接遍历json，读取数据。
2.如果是需要把前端的List对象转换为json传到后台，param是ajax的参数，那么转换如下所示：

1 2 3

var jsonStr = JSON.stringify(list); var param= {}; param.jsonStr=jsonStr;

在后台：
1.把String转换为List(str转换为list)

1 2 3

List<T> list = new ArrayList<T>(); JSONArray jsonArray = JSONArray.fromObject(str);//把String转换为json list = JSONArray.toList(jsonArray,t);//这里的t是Class<T>

2.把List转换为json

1 2	JSONArray json = JSONArray.fromObject(object); String str = json.toString();//把json转换为String

eg:
1. 根据页面用户输入的信息形成 Answer 对象的List 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

/**   * @param answers   * @param question_ids   * @param types   * @return   */  private List<Answer> toAnswerList(String[] studenAnswers, int[] question_ids,    int[] types,int[] scores) {   List<Answer> answerList = new ArrayList<Answer>();        if(studenAnswers!=null && question_ids!= null && types!= null&& scores!= null){    for (int i = 0; i < studenAnswers.length; i++) {            Answer answer = new Answer();     String studenAnswer = studenAnswers[i];     int type = types[i];     int question_id = question_ids[i];     int score = scores[i];                 answer.setQuestion_id(question_id);     answer.setScore(score);     answer.setStudenAnswer(studenAnswer);     answer.setType(type);            answerList.add(answer);    }   }   return answerList;  }     /**   * 将一个json字串转为list   * @param props   * @return   */  public static List<Answer> converAnswerFormString(String answer){   if (answer == null || answer.equals(""))    return new ArrayList();      JSONArray jsonArray = JSONArray.fromObject(answer);   List<Answer> list = (List) JSONArray.toCollection(jsonArray,     Answer.class);        return list;  }

2. 将一个 Answer 对象的List 生成Json字串，是根据客户端页面用户输入的信息生成的 

1 2 3 4 5 6 7 8

public String getAnswerString(String[] studenAnswers, int[] question_ids,   int[] types,int[] scores) {  List list = toAnswerList(studenAnswers, question_ids,     types, scores);  JSONArray jsonarray = JSONArray.fromObject(list);    return jsonarray.toString(); }