向Java应用程序通知数据库更改

Question

I'm trying to build a task-manager application. Two or more client applications should be able to change (such as mark off or change the title etc) certain tasks stored in the database over the web.

While creating the requirements, the following question came up:

How is it possible to inform client applications (Android Apps, Java-Applications on a Mac) about changes in the database, without constantly checking the database? I planned on storing the data objects in a SQL-Database on a Webserver. Should I use another database? What is the standard way to go right now in SE world? Any keywords for me or explanations would help!

Answer 1

Firstly, make sure you are not accessing the database directly from the client applications, that's a very dangerous route.

Secondly, as for your requirement it looks like you want a server side push notification.

As far as I know there are 3 ways to do this.

1. Check updates from the server every X seconds (if you don't have too many clients that needs to be notified this way is okay to go)
2. Use HTTP long polling.
3. Use WebSocket to keep a long lasting connection between server/client applications.

For mobile devices though, if you want to be notified even when the app is closed, take a look at all the push notification frameworks available out there (eg FCM/GCM).