Java Eclipse - 尝试从JSON读取时'位置0处的意外标记END OF FILE'

Question

我正在使用Java Eclipse创建一个事件管理系统，它将编写和读取JSON文件。这里我有代码创建一个新的JSON文件...

public void actionPerformed(ActionEvent arg0) {

        //Declaration of variables
        String title = txtTitle.getText();
        String month = (String) cboMonth.getSelectedItem(); 
        String day = (String) cboDate.getSelectedItem();
        String year = (String) cboYear.getSelectedItem();
        String location = txtLocation.getText();
        String description = txtDescription.getText();
        String URL = txtURL.getText();

        // Combine multiple variables together to make a single variable
        String date = month + "" + day + "" + year;

        // Create a new instance of the class called 'Event'
        Event event = new Event();

        // Assign values to the getter/setter methods of this instance
        event.setName(title);
        event.setDate(date);
        event.setLocation(location);
        event.setDesc(description);
        event.setURL(URL);

        // Add this new instance to the 'eventList' array list 
        MainMenu.eventList.add(event);


        // Create a new instance of the class called 'Event'
        JSONObject JSONEvent = new JSONObject();

        // Add data to the JSON file
        JSONEvent.put("Title", title);
        JSONEvent.put("Date", date);
        JSONEvent.put("Location", location);
        JSONEvent.put("Description", description);
        JSONEvent.put("URL", URL);

        // Create a new JSON file called 'Events.json' that has elements added to it
        try (FileWriter file = new FileWriter("Events.json", true)) {

            file.write("\n");
            file.write(JSONEvent.toJSONString());
            file.flush();

        // Error Handling
        } catch (IOException e) {
            e.printStackTrace();
        }
        }

通过创建JSON文件并使用JSONObjects填充它，此代码可以正常工作。这是JSON文件中单个条目的图像...... Single JSON Element

然后我有一个单独的类，下面的代码试图读取JSON文件并将其内容输出到控制台...

public static void main(String[] args) {

 JSONObject JSONEvent;

 String line = null;


try {
  FileReader fileReader = new FileReader("Events.json");

  BufferedReader bufferedReader = new BufferedReader(fileReader);

  while((line = bufferedReader.readLine()) != null) {
  JSONEvent = (JSONObject) new JSONParser().parse(line);

  String title = (String) JSONEvent.get("Title");
  System.out.println(title);

  String date = (String) JSONEvent.get("Date");
  System.out.println(date);

  String location = (String) JSONEvent.get("Location");
  System.out.println(location);

  String description = (String) JSONEvent.get("Description");
  System.out.println(description);

  String URL = (String) JSONEvent.get("URL");
  System.out.println(URL);

  Event event = new Event();
  event.setName(title);
  event.setDate(date);
  event.setLocation(location);
  event.setDesc(description);
  event.setURL(URL);

  MainMenu.eventList.add(event);

  }


  bufferedReader.close();

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

}
}

当我运行此代码时，我在控制台中得到以下错误... Unexpected token END OF FILE at position 0

有谁知道这个错误意味着什么？

Answer 1

你写入文件的第一件事是空行：

file.write("\n");

因此，在读取文件时，您尝试将空字符串解析为JSON，因此例外：解析器在有机会解析任何内容之前找到其输入的结尾。

而不是依赖于生成的JSON的内部格式，并将几个不同的JSON对象写入文件，在文件中一次编写单个对象数组（替换其先前的内容）会更简单，更安全，并在内存中一次读取整个数组。