Handling Commands

HandlerRegistry configuration

To listen a Command you should register it in the HandlerRegistry and make it available as a Bean.

Listening Commands

@Configuration
public class HandlerRegistryConfiguration {

    @Bean
    public HandlerRegistry handlerRegistry(CommandsHandler commands) {
        return HandlerRegistry.register()
                .handleCommand("some.command.name", commands::handleCommandA, Object.class/*change for proper model*/);
    }
}

To effectively start listening commands you should add the annotation @EnableCommandListeners to your MainApplication class or any other spring Configuration class, for example the CommandsHandler class can be like:

@EnableCommandListeners
public class CommandsHandler {
    
    public Mono<Void> handleCommandA(Command<Object/*change for proper model*/> command) {
        System.out.println("command received: " + command.getName() + " ->" + command.getData());
        return Mono.empty();
    }

}

As the model of commands is direct, a consumer always can send commands to the service provider, by this reason you may receive commands that you don`t have configured.

Listening Raw Commands

If you need direct access to the raw message from RabbitMQ without domain model conversion, you can use RawCommandHandler. Raw command handlers process all incoming commands without filtering by command name. This is useful when you need to handle the message body, headers, or other low-level properties directly.

@Configuration
public class HandlerRegistryConfiguration {

    @Bean
    public HandlerRegistry handlerRegistry(CommandsHandler commands) {
        return HandlerRegistry.register()
                .handleRawCommand(commands::handleRawCommandA);
    }
}

The handler implementation receives a RawMessage which can be cast to RabbitMessage to access the underlying message properties:

@EnableCommandListeners
public class CommandsHandler {
    
    public Mono<Void> handleRawCommandA(RawMessage command) {
        RabbitMessage rawMessage = (RabbitMessage) command;
        System.out.println("RawCommand received: " + new String(rawMessage.getBody()));
        System.out.println("Content Type: " + rawMessage.getProperties().getContentType());
        System.out.println("Headers: " + rawMessage.getProperties().getHeaders());
        // Process the raw message
        return Mono.empty();
    }
}

Wildcards

You may need to handle variable command names that have the same structure, in that case you can specfy a pattern with '*' wildcard, for example:

@Configuration
public class HandlerRegistryConfiguration {

    @Bean
    public HandlerRegistry handlerRegistry(CommandsHandler commands) {
        return HandlerRegistry.register()
                .handleCommand("send.*.notification", commands::handleCommandA, Object.class/*change for proper model*/);
    }
}

So any consumer can send a command with a name that matches with pattern, for example: send.email.notification

Example

You can see a real example at samples/async/async-receiver-responder