README.md

Axon 3.x CDI support

This is a small library to use Axon 3.x inside a (JEE) CDI container

CDI Parameter resolving

Axon has a builtin DI (dependency injection) concept for command handlers called parameter resolving. Parameter resolving takes place before your command handler is called. For each parameter following the command message payload, Axon tries to resolve the actual value and injects it into the method call. For a deeper explanation see the axon documentation for command handlers:

Axon documentation on command handlers

To use the Axon parameter resolving in a CDI environment you have add the CdiParameterResolverFactory to the configuration.

Let's take an example. Given a standard command handler:

public class MyCommandHandler {
    @CommandHandler
    public void handle(MyCommand command, MyDependecy myDependecy) {
        myDependecy.doSomething();
    }
}

And the following CDI bean in your application:

public class MyDependency {
    public void doSomething() {
        System.out.println("Done");
    }
}

You can then add the CdiParameterResolverFactory to your Axon configuration by doing something like this:

import de.novity.axon.cdi.CdiParameterResolverFactory;
import de.novity.axon.cdi.test.it.model.SimpleCommandHandler;
import org.axonframework.config.Configuration;
import org.axonframework.config.ConfigurationParameterResolverFactory;
import org.axonframework.config.DefaultConfigurer;
import org.axonframework.messaging.annotation.ClasspathParameterResolverFactory;
import org.axonframework.messaging.annotation.MultiParameterResolverFactory;
import org.axonframework.messaging.annotation.ParameterResolverFactory;

import javax.enterprise.context.ApplicationScoped;
import javax.enterprise.inject.Disposes;
import javax.enterprise.inject.Produces;

public class AxonConfigurationProducer {
    @ApplicationScoped
    @Produces
    public Configuration configuration(CdiParameterResolverFactory cdiParameterResolverFactory) {
        final Configuration configuration = DefaultConfigurer
                .defaultConfiguration()
                .registerComponent(ParameterResolverFactory.class, config -> MultiParameterResolverFactory.ordered(
                        new ConfigurationParameterResolverFactory(config),
                        ClasspathParameterResolverFactory.forClass(getClass()),
                        cdiParameterResolverFactory
                ))
                .registerCommandHandler(config -> new SimpleCommandHandler())
                .buildConfiguration();

        configuration.start();

        return configuration;
    }

    public void shutdownConfiguration(@Disposes Configuration configuration) {
        configuration.shutdown();
    }
}