如何从JSON文件中删除项目？

Question

I'm new to JSON and GSON and as well as Java. Currently I'm having difficulties on removing items in my Json files. Below are my code

public void removeUser() throws IOException{
    File accounts = new File("accounts.json");
    delete(accounts);
}

void delete(File acc) throws IOException {
    if (acc.exists()) {
        List userlist = new ArrayList();
        Iterator<Users> iterator = userlist.iterator();
        while (iterator.hasNext()) {
            if (iterator.next().getUsername().equals(deleteTxt.getText())) {
                iterator.remove();
                notifications();
                deleteTxt.setText(null);
                notificationLbl.setText("Wish granted!");

                break;

            }
        }
    }
}

and for my json's file structure

{ "username": "admin", "password": "21232f297a57a5a743894a0e4a801fc3", "roles": "admin" }, { "username": "client", "password": "21232f297a57a5a743894a0e4a801fc3", "roles": "client" }

Thing I wanted it to happen: When I pressed deleteBtn, removeUser() will be executed and the users and the details will be removed.

Thing that's happen: Nothing happen

Can anyone guide me on how to do remove?

Answer 1

sample code to read a jsonarray from a file , modify into a new array and store it back using apache-commons-io.jar

import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;

import org.apache.commons.io.FileUtils;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public static void delete(String username) throws JSONException, IOException {
        File file = new File("E:\\accounts.json");
        String encoding = Charset.defaultCharset().toString();
        JSONArray oldDataArray = new JSONArray(FileUtils.readFileToString(file, encoding));
        System.out.println(oldDataArray);
        JSONArray newDataArray = new JSONArray();
        for(int n=0;n<oldDataArray.length();n++) {
            JSONObject nthObject = oldDataArray.getJSONObject(n);
            if(!username.equals(oldDataArray.getJSONObject(n).get("username"))) {
                newDataArray.put(nthObject);
            }
        }
        System.out.println(newDataArray);
        FileUtils.writeStringToFile(file, newDataArray.toString(), encoding);
    }