如何在 Java 中将 ArrayList 转换为 JSON 数组？答案

【问题标题】：How to transform an ArrayList to JSON Array in Java?如何在 Java 中将 ArrayList 转换为 JSON 数组？
【发布时间】：2022-10-17 16:30:03
【问题描述】：

我想将收集到的 tagID 放入 epc（阵列内的 json 对象）并将默认天线端口值设置为“1”，但每次我的循环运行时，所有 tagID 都会卡在一行上。

到目前为止，这是我的代码。

JSONObject jsonObject = new JSONObject();
    try {
        //Settings up array
        JSONObject jObj = new JSONObject();
        JSONArray jArry = new JSONArray();
    
        //this arraylist is contains of arraylist with tagIDs 
        ArrayList<InventoryListItem> arr = Application.tagsReadInventory;
                                    
        int position = 0;
                                    
        //this arraylist is where i put my collected tagIDs
        ArrayList<String> tagIDs = new ArrayList<>();
 
        //looping to get tagIDs from "Application.tagsReadInventory" and put it in tagIDs arraylist
        for (position = 0; position < arr.size(); position++) {
            tagIDs.add(arr.get(position).getTagID());
            jObj.put("epc",tagIDs);
            jObj.put("antennaPort", 1);
            jArry.put(jObj);
         }
    
         jsonObject.put("reader_name", ReaderIP);
         jsonObject.put("mac_address", "asd");
         jsonObject.put("tag_reads", jArry);
   
} catch (JSONException e) {
   e.printStackTrace();
}

我想要这样的json格式。

{
  "reader_name": "192.168.1.332",
  "mac_address": "asd",
  "tag_reads": [
        {
        "epc": "474103534923303031343431",
        "antennaPort": 1
        },
        {
        "epc": "474103534923303031333232",
        "antennaPort": 1
        },
        {
        "epc": "47410353492330303035303D",
        "antennaPort": 1
        }
    ]
}

但这就是我的结果。

{
  "reader_name": "192.168.1.44",
  "mac_address": "asd",
  "tag_reads": [
        {
        "epc": "474103534923303031343431","474103534923303031343431","474103534923303031343431"
        "antennaPort": 1
        }
    ]
}

【问题讨论】：

标签： java arrays json arraylist

【解决方案1】：

我已经通过添加一个新的 foreach 来获取我的 tagIDs arraylist 的每个列表来做到这一点，并且它工作得很好。

JSONObject jsonObject = new JSONObject();
    try {
 
      //Settings up array
      JSONArray jArry = new JSONArray();
    
      //this arraylist is contains of arraylist with tagIDs
      ArrayList<InventoryListItem> arr = Application.tagsReadInventory;
    
      int position = 0;
    
      //this arraylist is where i put my collected tagIDs from "Application.tagsReadInventory"
      ArrayList<String> tagIDs = new ArrayList<>();
  
      //looping to get tagIDs from "Application.tagsReadInventory" and put it in tagIDs arraylist
       for (position = 0; position < arr.size(); position++) {                        
           tagIDs.add(arr.get(position).getTagID());
       }
    
       //get each of the list inside tagIDs arraylist
       for (String tags : tagIDs) {
           JSONObject jObj = new JSONObject();
           jObj.put("epc",tags);
           jObj.put("antennaPort", 1);
           jArry.put(jObj);
       }
    
     jsonObject.put("reader_name", ReaderIP);
     jsonObject.put("mac_address", "asd");
     jsonObject.put("tag_reads", jArry);
    
  } catch (JSONException e) {
        e.printStackTrace();
  }

【讨论】：