Module 13: Creating a Facebook Clone
Transcript
the changes to the notification service are significant and in effect that’s the class that implements push notification calls from the server before we start we need to add a few fields to the class these will be used by the code we introduced soon these are besides the keys field i mentioned before this is the url of the codename one push server we’ll use that to send out push messages logging is used for errors in the body of the class we need to inject the user’s repository now as we need to find the user there the first step is trivial it’s about mapping the push key to the service class which is exactly what we do here on push registration we invoke this method to update the push key in the user object if the push server indicates that a push key is invalid or expired we delete that key a fresh key will be created the next time the user runs the app the second method is internal to the server and isn’t exposed as a web service but the former method is the next stage is the push notification itself we add these lines to the send notification method notice that a push key can be null since it can expire or might not be registered yet this leads us to the send push notification method but we’ll get there via detour this method is based on the server push code from the developer guide notice that this is the import method not the method we invoked before we’ll go through this first and then reach that code we connect to the push server url to send the push message a standard form post submission request is used we fetch the values for the fields that can defer specific specifically the certificate and passwords which vary between production and development we send all the details as a post request to the codename one push server which then issues a push to the given device type the server can return 200 in case of an error but if the response isn’t 200 then it’s surely an error the server response is transformed to a string for passing on the next method i’ll cover the read input stream method soon we need to go over the responses from the push server these responses would include information such as push key expiration and we would need to purge that key from our database that’s all done in the actual method for sending push messages the async annotation indicates this method should execute on a separate thread this is handled by spring we’ll discuss that soon senpush impul returns json with messages which we need to process the spring json parsing api has different forms for map list but we can get both in the response from the server so we need to check if it’s a list then it’s a device list with either acknowledgement of sending for android only or error messages if we have an error message for a specific device key we need to remove it to prevent future problems with the push servers if we got a map in response it could indicate an error which we currently don’t really handle other than through logging if push doesn’t work the app would still work fine you’ll just need to refresh manually a better implementation would also use a fallback for cases of push failure for instance websocket but it’s not essential at least not at first we referenced read input stream in the previous code blocks it’s defined in the code as such i could have written more modern code using nio but i was running out of time and i had this code handy it does the job well next we expose the push registration method as a restful web service this is a direct mapping to the update method so there isn’t much to say about that the last piece of the server code is the changes we need to make to the facebook clone server application class we didn’t touch that class at all when we started off but now we need some changes to support the asynchronous send push notification method first we need the at enable async annotation so at async will work in the app the at bin for the async executor creates the thread pool used when we invoke an at async method we define reasonable capacities we don’t want an infinite queue as we can run out of ram and it can be used in a denial of service attack we also don’t want too many threads in the pool as our server might overcrowd the push servers and receive rate limits this level should work fine with that the server side portion of the push support is done