google-calendar-api | Demo Project for Google Calendar API Using Spring Boot Rest | REST library

I am working on a spring boot project where I am integrating my api with google calendar api.While running the application I am getting this error:

I have read a lot of articles :

Google Calendar API - PHP https://developers.google.com/calendar/quickstart/php

and others.. I want to use the service account, I gave permissions for my calendar, I have downloaded the json key. If I use the code from Google, I got:

missing the required redirect URI

If i use the code:

I am trying to use google push notification for calendar to be notified if a user's event's start or/and end dateTime changes.

I have followed all the steps from push doc regarding registering and verifying my domain.

My code is as follows:

I am trying to get the calendar event so I can then update it as the document shows.

My assumption was that an event with such JSON:

Applications in GSuite can have domain-wide delegation (DWD) enabled, allowing the application to access user data (and other domain data) without any interaction on the part of the users.

According to a Google Support article, it is implied that the application is limited by the scopes set on the application.

However, reading various responses on Stack Exchange regarding "user impersonation" makes me wonder about the validity of this. See:

• Breno's response "The domain-wide delegation model allows a service account to impersonate a user and thus obtain the same privileges in the domain that the user identity + set of scopes granted to the application imply."
• Kessy's and Gilfoyle's responses "...This means that the service account only has access to data from the account the application is impersonating...." and "...First and foremost: A service account is technically a superadministrator once DWD ..."
• Edited question ("Solution")

There is nothing concrete, but it appears (possibly incorrectly) that once an application impersonates the "right" user with sufficient admin privileges, any required data can be accessed. I've trawled through the Google Support documentation, but there is very little about scopes with regards to impersonating users that I could find. I haven't the experience building such an application to know what to look for.

My questions:

(Q) Can applications with DWD enabled do more than the scopes allow by impersonating a superadmin? If not, if one of those scopes includes the authority to change the user password (e.g. https://www.googleapis.com/auth/admin.directory.user), doesn't that mean an application can bootstrap itself and add any other, needed scopes?

Alternatively, are applications with DWD limited by their scopes, even when impersonating a super admin?

I'm not a developer; I'm a system admin with very some light/informal dev experience, so I would be greatly appreciative if you could pitch your answers accordingly.

Based on this answer by @Ilya, I have created this code:

I'm pretty new at this but I've been trying to use the google calendar API to show upcoming events on a website I'm making. So far I've enabled the API and created a service account to access the calendar. I've been using the instructions from another stackoverflow post but I keep getting an error. I believe this is the code that is causing it:

I am using google-calendar-api to add a new event. When I send the invitation to the attendees, the event is added to their calendar but they are not get notification to the email:

I have created a service account to access a certain google calendar. this service account user also got the permission in the calendar settings as is described in this blog: "allow my user to add meeting in my calendar with Google Calendar API with PHP without auth".

As I can see in Google Cloud Platform under APIs + Services -> Credentials in the Service Account section the created service account is used with all services (last 30 days) every time, when I fire this php script, but in the browser window I get no error, that there would be a problem with authentication but: Uncaught Error: Call to a member function getSummary() on null in line... of the php-script Script and Settings in Google Cloud Platform are as described in the mentioned post.

Any idea what could be the problem? Has there anything changed with google calendar api since this post in 2019?