6.27.2 Configuring the Netty Pipeline

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

Both the Netty HTTP server and client implement this interface and it allows you to 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 demonstrates registing 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.*;
import io.micronaut.http.netty.channel.ChannelPipelineCustomizer;
import org.zalando.logbook.Logbook;
import org.zalando.logbook.netty.*;
import javax.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.*
import io.micronaut.http.netty.channel.ChannelPipelineCustomizer
import io.netty.channel.ChannelPipeline
import org.zalando.logbook.Logbook
import org.zalando.logbook.netty.*
import javax.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.getBean()
        if (customizer.isServerChannel()) { (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.*
import io.micronaut.http.netty.channel.ChannelPipelineCustomizer
import io.netty.channel.ChannelPipeline
import org.zalando.logbook.Logbook
import org.zalando.logbook.netty.*
import javax.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
    }
}