package com.google.sps.servlets;

import com.google.appengine.api.users.UserService;
import com.google.appengine.api.users.UserServiceFactory;
import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;
import com.google.appengine.api.datastore.Key;
import com.google.appengine.api.datastore.KeyFactory;
import com.google.appengine.api.datastore.EntityNotFoundException;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import com.google.gson.Gson;
import com.google.sps.tool.ResponseHandler;
import com.google.sps.data.Folder;

@WebServlet("/editfolder")
public class EditFolderServlet extends HttpServlet{
  
  @Override
  public void doPut(HttpServletRequest request, HttpServletResponse response) throws IOException {
    
    UserService userService = UserServiceFactory.getUserService();

    if (userService.isUserLoggedIn()) {
      String newFolderName = request.getParameter("folderName");
      String newFolderDefaultLanguage = request.getParameter("folderDefaultLanguage");
      String folderKey = request.getParameter("folderKey");
      updateFolder(response, newFolderName, newFolderDefaultLanguage, folderKey);
    }
  }

  private void updateFolder(HttpServletResponse response, String newFolderName, String newFolderDefaultLanguage, String folderKey) throws IOException {
    DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
    Entity folder = getExistingFolderInDatastore(response, datastore, folderKey);
    setFolderWithRequestedEdits(folder, newFolderName, newFolderDefaultLanguage);
    datastore.put(folder);
  }

  private Entity getExistingFolderInDatastore(HttpServletResponse response, DatastoreService datastore, String folderKey) throws IOException {
    Entity folder;
    try {
      folder = datastore.get(KeyFactory.stringToKey(folderKey));
    } catch (EntityNotFoundException e) {
      ResponseHandler.sendErrorMessage(response, "Cannot edit Folder at the moment");
      folder = null;
    }

    return folder;
  }

  private void setFolderWithRequestedEdits(Entity folderEntity, String newFolderName, String newFolderDefaultLanguage) throws IOException {
    folderEntity.setProperty("folderName", newFolderName);
    folderEntity.setProperty("folderDefaultLanguage", newFolderDefaultLanguage);
  }
}

package com.google.sps.servlets;

import com.google.appengine.api.users.UserService;
import com.google.appengine.api.users.UserServiceFactory;
import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;
import com.google.appengine.api.datastore.Key;
import com.google.appengine.api.datastore.KeyFactory;
import com.google.appengine.api.datastore.EntityNotFoundException;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import com.google.gson.Gson;
import com.google.sps.tool.ResponseHandler;
import com.google.sps.data.Folder;

@WebServlet("/editfolder")
public class EditFolderServlet extends HttpServlet{
  
  @Override
  public void doPut(HttpServletRequest request, HttpServletResponse response) throws IOException {
    UserService userService = UserServiceFactory.getUserService();

    if (userService.isUserLoggedIn()) {
      String newFolderName = request.getParameter("folderName");
      String newFolderDefaultLanguage = request.getParameter("folderDefaultLanguage");
      String folderKey = request.getParameter("folderKey");
      updateFolder(response, newFolderName, newFolderDefaultLanguage, folderKey);
    }
  }

  private void updateFolder(HttpServletResponse response, String newFolderName, String newFolderDefaultLanguage, String folderKey) throws IOException {
    DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
    Entity folder = getExistingFolderInDatastore(response, datastore, folderKey);
    
    if (folder == null) {
        ResponseHandler.sendErrorMessage(response, "Cannot edit Folder at the moment");
    }
    
    setFolderWithRequestedEdits(folder, newFolderName, newFolderDefaultLanguage);
    datastore.put(folder);
  }

  private Entity getExistingFolderInDatastore(HttpServletResponse response, DatastoreService datastore, String folderKey) throws IOException {
    Entity folder;
    try {
      return datastore.get(KeyFactory.stringToKey(folderKey));
    } catch (EntityNotFoundException e) {
      return null;
    }
  }

  private void setFolderWithRequestedEdits(Entity folderEntity, String newFolderName, String newFolderDefaultLanguage) throws IOException {
    folderEntity.setProperty("folderName", newFolderName);
    folderEntity.setProperty("folderDefaultLanguage", newFolderDefaultLanguage);
  }
}

Fix level of abstraction in EditFolderServlet