AWS Cognito and DynamoDB - amazon-web-services

Question

I've been looking around a lot, but I couldn't find a (definite) solution to a seemingly very simply problem.
I'm trying to create a database with user-specific data (for instance, their favorite color, etc). Creating it with DynamoDB is fine, so is editing it; my issue is with identifying the user in the first place (I'm using Cognito), I couldn't find a "best practice" anywhere that would be secure and efficient to use.
In other words, I have the login part and the database part. But how can I - on an arbitrary page - get who the logged-in user is in order to fetch the appropriate row in the database (for instance, having a table with the "sub" as the primary key).
So far, I've found a small guide on using JWT and carrying around what seems to be a session token that I can use to get back user information. I'm not quite sure if this is safe or a good practice, and I'm fairly lost on what to do. Any advice on the best practices, or what is the "right" way would be appreciated.

Answer 1

"how can I - on an arbitrary page - get who the logged-in user"
This all depends on the framework you are using. For example, if you built an AWS application using Spring Security and Cognito, you can easily get the logged in user using code like this in a Java Controller:
#RequestMapping(value = "/user", method = RequestMethod.GET)
#ResponseBody
public String getItems(HttpServletRequest request, HttpServletResponse response) {
String logUser = request.getUserPrincipal().getName();
return logUser;
}
I just tested this logic with a Java web app that uses Cognito and it works perfectly:
You need to find the equivalent logic for the framework you are using to build an app that requires a user to log in.
Once you have the user name, you can use the DynamoDB API to look up more user details. If you are using Java, you can use the Java API to do so. If using JavaScript, use the JavaScript API.