MediatR

Simple mediator implementation in Java.

Greatly inspired by jbogard's .NET implementation.

MediatR Configuration

Add MediatR to your build.gradle

implementation 'io.github.lucasbuccilli:mediatR:1.0.2'

Create a MediatR bean

@Configuration
public class MediatRConfig {
    @Bean
    public MediatR mediatR(ApplicationContext applicationContext) {
        return MediatRFactory.getMediatR(applicationContext);
    }
}

Using MediatR

MediatR has two kind of messages it dispatches:

Request/response messages, dispatched to a single handler

• Request<T>
• RequestHandler<T extends Request>

Event messages, dispatched to multiple handlers

• Event
• EventHandler<T extends Event>

Requests and Request Handlers

Create a request

public class GetUserRequest implements Request<User> {
    private int userId;
    ...
}

Create a handler

Note: A handler must be annotated with @Component or @Service

@Component
public class GetUserRequestHandler implements RequestHandler<GetUserRequest> {
    @Override
    public User handle(GetUserRequest request) {
        ...
        return user;
    }
}

Send the request with MediatR and tada

var user = mediatR.send(new GetUserRequest(1));

Events and Event Handlers

Events are similar to requests, but you can register multiple handlers for the same event.

public class DeleteUserEvent implements Event {
    private int userId;
    ...
}

@Component
public class DeleteUserEventHandlerOne implements EventHandler<DeleteUserEvent> {
    @Override
    public void handle(DeleteUserEvent event) {
        ...
    }
}

@Component
public class DeleteUserEventHandlerTwo implements EventHandler<DeleteUserEvent> {
    @Override
    public void handle(DeleteUserEvent event) {
        ...
    }
}

mediatR.send(new DeleteUserEvent(1));

Async

MediatR also supports asynchronous operations

CompletableFuture<User> userFurure = mediatR.sendAsync(new GetUserRequest(1));

CompletableFuture<Void> userFurure = mediatR.sendAsync(new DeleteUserEvent(1));