如何在Java中将JSONObject写入其中包含JSONArray的文件？

Question

我有JSON文件,我需要再次阅读,编辑和写出.

阅读工作正常,我在数据中与JSON数组的写入部分斗争.

我使用JSON.simple库来处理Java中的JSON.

该文件如下所示:

{
    "maxUsers":100,
    "maxTextLength":2000,
    "maxFileSize":2000,
    "services":
    [
        {
            "serviceName":"?????c",
            "className":"YandexConnector.class",
            "isEnabled":true
        },

        {
            "serviceName":"Google",
            "className":"GoogleConnector.class",
            "isEnabled":false
        }
    ]
}

当我尝试将JSON数据(变量obj)写入文件时,该services数组被破坏.我的写作代码:

JSONObject obj = new JSONObject();
obj.put("maxUsers", this.getMaxUsers());
obj.put("maxTextLength", this.getMaxTextLength());
obj.put("maxFileSize", this.getMaxFileSize()); 

JSONArray servicesJSON = new JSONArray();
ArrayList<Service> servicesArray = this.getServices();
for(int i=0; i< servicesArray.size(); i++)
{
    servicesJSON.add(servicesArray.get(i));
}
obj.put("services", servicesJSON);


FileWriter file = new FileWriter(filename);                
obj.writeJSONString(file);
file.flush();
file.close();

这输出:

{
    "services":
    [
        translator.settings.Service@121c5df,
        translator.settings.Service@45f4ae
    ],
    "maxTextLength":2000,
    "maxUsers":100,
    "maxFileSize":2000
}

如何将JSON数据正确地写入文件,如果我在JSONArray中这样做services？

---

代码,我从文件中读取JSON数据(工作正常):

JSONParser parser = new JSONParser();
Object obj = parser.parse(new FileReader(filename));
JSONObject jsonObject = (JSONObject) obj;

setMaxUsers((Long) jsonObject.get("maxUsers"));
setMaxTextLength((Long) jsonObject.get("maxTextLength"));
setMaxFileSize((Long) jsonObject.get("maxFileSize"));
// get all list of services
JSONArray serv = (JSONArray) jsonObject.get("services");

for (int i = 0; i < serv.size(); i++) {
    JSONObject service = (JSONObject) serv.get(i);
    Service servec = new Service();
    servec.setServiceName((String) service.get("serviceName"));
    servec.setClassName((String) service.get("className"));
    servec.setIsEnabled((Boolean) service.get("isEnabled"));

    services.add(i, servec);
}

编辑部分尚未编写,因此我在阅读后直接调用写作部分.

---

Answer 1

看一看的例子的JSON-simple.

它在这里说你需要将对象逐个放入数组中,只使用primitive和String值.您可以使用Collections类似Map或自行仅包含String或primitive值.

  JSONArray list = new JSONArray();
  list.add("foo");
  list.add(new Integer(100));
  list.add(new Double(1000.21));
  list.add(new Boolean(true));
  list.add(null);
  StringWriter out = new StringWriter();
  list.writeJSONString(out);

因此,添加您的Services是不允许的,不会起作用.您应该toMap在其中添加一个方法,将其转换为a Map并将fromMap其转换回来.

像这样(in Services.java):

 public Map toMap() {
     HashMap<String, String> serviceAsMap = new HashMap<>();
     servicesAsMap.put("serviceName", serviceName);
     servicesAsMap.put("className", this.class.getName() + ".class");
     servicesAsMap.put("isEnabled", isEnabled);
     // ... continue for all values
     return servicesAsMap;
 }

然后你可以使用它Map来填充你JSONArray喜欢这个:

        JSONArray servicesJSON = new JSONArray();
        ArrayList<Service> servicesArray = this.getServices();
        for(int i=0; i< servicesArray.size(); i++)
        {
            servicesJSON.add(servicesArray.get(i).toMap()); // use the toMap method here.
        }
        obj.put("services", servicesJSON);