Creating a Facebook Clone - Part XXIII - Transcript.pdf

Creating a Facebook Clone - Part XXIII
The NotificationService is arguably one of the simplest services we have right now. Its main reason for existence is push notification that we'll integrate into it later on.

@Service
public class NotificationService {
@Autowired
private NotificationRepository notifications;
public void sendNotification(User u, NotificationDAO nd) {
Notification n = new Notification();
n.setDate(System.currentTimeMillis());
n.setReaction(nd.getReaction());
n.setReactionColor(nd.getReactionColor());
n.setText(nd.getText());
n.setUser(u);
n.setWasRead(nd.isWasRead());
notifications.save(n);
}
public List<NotificationDAO> listNotifications(String authtoken,
int page, int amount) {
Page<Notification> notificationsPage = notifications.
findNotificationsForUser(
authtoken, PageRequest.of(page, amount,
Sort.by(Sort.Direction.DESC, "date")));
NotificationService
As I said the class is trivial and contains just 2 methods.

The only repository is the notification repository as we don’t need access to anything else for this service.

@Service
@Autowired
n.setUser(u);
}
NotificationService
sendNotification is important as this would be a great location to send push notification or trigger a websocket based push in the future

@Service
@Autowired
n.setUser(u);
}
NotificationService
Right now we just save the data to the database which we would do anyway as we want to keep track of notifications

n.setUser(u);
}
List<NotificationDAO> resp = new ArrayList<>();
for(Notification c : notificationsPage) {
resp.add(c.getDAO());
}
return resp;
}
}
NotificationService
This is an API for the client side so it can list the notifications pending to the user, it accepts a page number so we can go through pages of results

n.setUser(u);
}
}
return resp;
}
}
NotificationService
When we go through the notification pages we also pass the sort value to indicate we want notifications arranged by data

n.setUser(u);
}
}
return resp;
}
}
NotificationService
The return value is the DAO's for the current page carrying the notification data. The send notification API is an API designed for the server side. Notifications only
originate within the server to prevent abuse by a malicious client.

@Service
public class MediaService {
@Autowired
private MediaRepository media;
@Autowired
private UserRepository user;
public String storeMedia(String authtoken, byte[] data,
String mimeType, String role, String visibility,
String filename) {
User u = user.findByAuthtoken(authtoken).get(0);
Media m = new Media();
m.setData(data);
m.setOwner(u);
m.setDate(System.currentTimeMillis());
m.setFilename(filename);
m.setMimeType(mimeType);
m.setRole(role);
m.setVisibility(visibility);
MediaService
We continue the trend of simple services with the MediaService which is almost as simple as the NotificationService.

The media service works with the media repository only but it needs to authenticate some actions against the user repository

@Service
@Autowired
@Autowired
String filename) {
m.setData(data);
m.setOwner(u);
m.setRole(role);
MediaService
When adding a new media we accept almost all the values from the client with the exception of time which we store in the server to prevent abuse

@Service
@Autowired
@Autowired
String filename) {
m.setData(data);
m.setOwner(u);
m.setRole(role);
MediaService
We need an auth token to make sure the media is saved under the correct user

@Autowired
@Autowired
String filename) {
m.setData(data);
m.setOwner(u);
m.setRole(role);
media.save(m);
return m.getId();
}
public MediaDAO getPublicMedia(String id) throws PermissionException {
Media m = media.findById(id).get();
if(VisibilityConstants.isPublic(m.getVisibility())) {
return m.getDAO();
MediaService
We return the media ID when we are done so it can be referenced by the user

m.setRole(role);
media.save(m);
return m.getId();
}
return m.getDAO();
}
throw new PermissionException(
"Media item belongs to a user that isn't a friend");
}
public MediaDAO getMedia(String authToken, String id) throws
PermissionException {
return m.getDAO();
}
if(!m.getOwner().getAuthtoken().equals(authToken)) {
if(!m.getOwner().isFriendByToken(authToken)) {
}
MediaService
Public media can be requested via the id of the media and doesn't require any authentication

media.save(m);
return m.getId();
}
return m.getDAO();
}
}
return m.getDAO();
}
}
}
return m.getDAO();
MediaService
public enum VisibilityConstants {
PUBLIC("public"), FRIENDS("friends");
private String str;
private VisibilityConstants(String str) {
this.str = str;
}
public String asString() {
return str;
}
public static boolean isPublic(String s) {
return s == null || s.equalsIgnoreCase(PUBLIC.asString());
}
}
We need to check that the user is indeed requesting a public media object and isn't spoofing a request.

This obviously brings up the visibility constants enum which is pretty trivial right now. We just have two visibility types for public & friend. As you can see the isPublic
method tests if the field is public or null.

media.save(m);
return m.getId();
}
return m.getDAO();
}
}
return m.getDAO();
}
}
}
return m.getDAO();
MediaService
public class PermissionException extends Exception {
public PermissionException(String message) {
super(message);
}
}
The permission exception is thrown otherwise.

That exception is pretty simple and again just a marker exception for the webservice layer

return m.getDAO();
}
}
return m.getDAO();
}
}
}
return m.getDAO();
}
}
MediaService
Finally for media that could potentially be private we need this method, it accepts the user token and media id

return m.getDAO();
}
}
return m.getDAO();
}
}
}
return m.getDAO();
}
}
MediaService
If the media is public then there is no problem we can just return it

return m.getDAO();
}
}
return m.getDAO();
}
}
}
return m.getDAO();
}
}
MediaService
If the media is for friends only we need to verify that the user requesting the media is indeed a friend

Creating a Facebook Clone - Part XXIII - Transcript.pdf

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Creating a Facebook Clone - Part XXIII - Transcript.pdf