Introduction Reactive Programming

Spring Reactive.

Reactive Programming is a declarative programming paradigm concerned with data streams and propagation of change.

• Imperative means where we write everything.
• Declarative means we just say what we need and it is done by default.

Reactive Programming is not async programming. It can be synchronous.

Use cases of Reactive Programming.

• User Events. When user clicks on the button you execute some function. We react to the button click.
• I/O Interaction. When some output is given based on the input.

Event Driven Programming. Some function trigger when button click.

@GetMapping("/users/{userId}")
public User getUserDetails(@PathVariable String userId){
    User user = userService.getUser(userId);
    UserPreferences prefs = userPreferenceService.getPreferences(userId);
    user.setPreferences(prefs);
    return user;
        }

In this code we are calling two methods and waiting for the first one to complete to start the next one. It is blocking. They are Unnecessarily Sequential.

The first thread will complete then the second thread will begin.

When web server gets a request it calls a thread. When it takes more time to respond to the request it means there are more threads. If we just call a thread and wait then it will increase the thread conuntand after a pointit cannot make new thread as it depends on hardware.

Reactive Programming with Spring Boot | A Beginner’s Guide