6.29.2 Configuring the Netty Pipeline

You can customize the Netty pipeline by writing a Bean Event Listener that listens for the creation of ChannelPipelineCustomizer.

Both the Netty HTTP server and client implement this interface and it lets you customize the Netty ChannelPipeline and add additional handlers.

The ChannelPipelineCustomizer interface defines constants for the names of the various handlers Micronaut registers.

As an example the following code sample demonstrates registering the Logbook library which includes additional Netty handlers to perform request and response logging:

Customizing the Netty pipeline for Logbook

import io.micronaut.context.annotation.Requires;
import io.micronaut.context.event.BeanCreatedEvent;
import io.micronaut.context.event.BeanCreatedEventListener;
import io.micronaut.http.netty.channel.ChannelPipelineCustomizer;
import org.zalando.logbook.Logbook;
import org.zalando.logbook.netty.LogbookClientHandler;
import org.zalando.logbook.netty.LogbookServerHandler;
import jakarta.inject.Singleton;
@Requires(beans = Logbook.class)
@Singleton
public class LogbookPipelineCustomizer
        implements BeanCreatedEventListener<ChannelPipelineCustomizer> { (1)
    private final Logbook logbook;
    public LogbookPipelineCustomizer(Logbook logbook) {
        this.logbook = logbook;
    }
    @Override
    public ChannelPipelineCustomizer onCreated(BeanCreatedEvent<ChannelPipelineCustomizer> event) {
        ChannelPipelineCustomizer customizer = event.getBean();
        if (customizer.isServerChannel()) { (2)
            customizer.doOnConnect(pipeline -> {
                pipeline.addAfter(
                    ChannelPipelineCustomizer.HANDLER_HTTP_SERVER_CODEC,
                    "logbook",
                    new LogbookServerHandler(logbook)
                );
                return pipeline;
            });
        } else { (3)
            customizer.doOnConnect(pipeline -> {
                pipeline.addAfter(
                        ChannelPipelineCustomizer.HANDLER_HTTP_CLIENT_CODEC,
                        "logbook",
                        new LogbookClientHandler(logbook)
                );
                return pipeline;
            });
        }
        return customizer;
    }
}

Customizing the Netty pipeline for Logbook

import io.micronaut.context.annotation.Requires
import io.micronaut.context.event.BeanCreatedEvent
import io.micronaut.context.event.BeanCreatedEventListener
import io.micronaut.http.netty.channel.ChannelPipelineCustomizer
import io.netty.channel.ChannelPipeline
import org.zalando.logbook.Logbook
import org.zalando.logbook.netty.LogbookClientHandler
import org.zalando.logbook.netty.LogbookServerHandler
import jakarta.inject.Singleton
@Requires(beans = Logbook.class)
@Singleton
class LogbookPipelineCustomizer
        implements BeanCreatedEventListener<ChannelPipelineCustomizer> { (1)
    private final Logbook logbook
    LogbookPipelineCustomizer(Logbook logbook) {
        this.logbook = logbook
    }
    @Override
    ChannelPipelineCustomizer onCreated(BeanCreatedEvent<ChannelPipelineCustomizer> event) {
        ChannelPipelineCustomizer customizer = event.bean
        if (customizer.serverChannel) { (2)
            customizer.doOnConnect( { ChannelPipeline pipeline ->
                pipeline.addAfter(
                        ChannelPipelineCustomizer.HANDLER_HTTP_SERVER_CODEC,
                        "logbook",
                        new LogbookServerHandler(logbook)
                )
                return pipeline
            })
        } else { (3)
            customizer.doOnConnect({ ChannelPipeline pipeline ->
                pipeline.addAfter(
                        ChannelPipelineCustomizer.HANDLER_HTTP_CLIENT_CODEC,
                        "logbook",
                        new LogbookClientHandler(logbook)
                )
                return pipeline
            })
        }
        return customizer
    }
}

Customizing the Netty pipeline for Logbook

import io.micronaut.context.annotation.Requires
import io.micronaut.context.event.BeanCreatedEvent
import io.micronaut.context.event.BeanCreatedEventListener
import io.micronaut.http.netty.channel.ChannelPipelineCustomizer
import io.netty.channel.ChannelPipeline
import org.zalando.logbook.Logbook
import org.zalando.logbook.netty.LogbookClientHandler
import org.zalando.logbook.netty.LogbookServerHandler
import jakarta.inject.Singleton
@Requires(beans = [Logbook::class])
@Singleton
class LogbookPipelineCustomizer(private val logbook: Logbook) :
    BeanCreatedEventListener<ChannelPipelineCustomizer> { (1)
    override fun onCreated(event: BeanCreatedEvent<ChannelPipelineCustomizer>): ChannelPipelineCustomizer {
        val customizer = event.bean
        if (customizer.isServerChannel) { (2)
            customizer.doOnConnect { pipeline: ChannelPipeline ->
                pipeline.addAfter(
                        ChannelPipelineCustomizer.HANDLER_HTTP_SERVER_CODEC,
                        "logbook",
                        LogbookServerHandler(logbook)
                )
                pipeline
            }
        } else { (3)
            customizer.doOnConnect { pipeline: ChannelPipeline ->
                pipeline.addAfter(
                        ChannelPipelineCustomizer.HANDLER_HTTP_CLIENT_CODEC,
                        "logbook",
                        LogbookClientHandler(logbook)
                )
                pipeline
            }
        }
        return customizer
    }
}