How to make a client fetch everytime data is updated?

Question

I have a project which consists of the following parts:

• Rest API (with Spring)
• web dashboard (uses the Rest API to manage data)
• Client (fetches data and works with it)

Now what im asking myself is, how can I make sure that the client fetches the new data as soon as it as updated through the web dashboard? Fetching every few seconds doesn't seem like the right approach, would a socket connection be a good solution?

Please let me know if you have any ideas, thank you.

Answer 1

As an option, you could send a message to a queue when a table row is created/updated/deleted. With that, you will have the changes asynchronously and you can react based on them.

In the publisher side you can have something like this:

import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Configurable;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationEventPublisher;

import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.PostPersist;
import javax.persistence.PostRemove;
import javax.persistence.PostUpdate;

import static javax.persistence.GenerationType.IDENTITY;

@Entity
@EntityListeners(ExamplePersonEntityListener.class)
class ExamplePerson {
    @Id
    @GeneratedValue(strategy=IDENTITY)
    private Long id;
    private String name;
    private String lastname;
}

@Configurable
class ExamplePersonEntityListener extends AbstractEntityyListener<ExamplePersonEntityApplicationEvent> {
    @PostPersist
    public void examplePersonCreated(ExamplePerson model) {
        this.broadcast(new ExamplePersonEntityApplicationEvent(EventActionn.CREATE, model));
    }

    @PostUpdate
    public void examplePersonUpdated(ExamplePerson model) {
        this.broadcast(new ExamplePersonEntityApplicationEvent(EventActionn.UPDATE, model));
    }

    @PostRemove
    public void examplePersonRemoved(ExamplePerson model) {
        this.broadcast(new ExamplePersonEntityApplicationEvent(EventActionn.DELETE, model));
    }
}

public class ExamplePersonEntityApplicationEvent extends EntityApplicationEventt<ExamplePerson> {
    protected ExamplePersonEntityApplicationEvent(EventActionn action, ExamplePerson model) {
        super(action, model);
    }
}

@Configurable
abstract class AbstractEntityyListener<T extends EntityApplicationEventt<?>> {

    @Autowired
    private ObjectFactory<ApplicationEventPublisher> appEvents;

    public final void setApplicationEventPublisher(ObjectFactory<ApplicationEventPublisher> appEvents) {
        this.appEvents = appEvents;
    }

    protected final void broadcast(T event) {
        assert this.appEvents != null;
        this.appEvents.getObject().publishEvent(event);
    }
}

class EntityApplicationEventt<T extends Object> extends ApplicationEvent {
    private final EventActionn action;
    private final T model;

    protected EntityApplicationEventt(EventActionn action, T model) {
        super(model);
        this.action = action;
        this.model = model;
    }

    public EventActionn getAction() {
        return this.action;
    }

    public Long getId() {
        return (Long)this.getSource();
    }

    public T getModel() {
        return this.model;
    }
}

enum EventActionn {
    CREATE,
    UPDATE,
    DELETE,
}

You will need to create a queue and the subscriber to the queue on the Client.

Answer 2

In general, there are two ways:

1. Push solution (As you mentioned) Ex: WebSocket/streaming
2. Using a webhook. You have to implement it yourself or use a webhook provider.