Monday, August 7, 2017

XRebel for standalone apps with embedded Jetty

XRebel was designed to work specifically with Java web applications. Currently, it relies on Servlet API to serve its UI. It has been tested with a range of application servers (Apache Tomcat, WildFly, WebSphere, and others) and some full stack frameworks as well, including Spring Boot and JavaSpark.

Sometimes however, you might want to use XRebel with a standalone Java process that is not using Servlet API. Hence, XRebel cannot display its embedded UI to render the data it collected from the application. What can we do about this? Well, XRebel is tested on Jetty and it works quite well there. Jetty is also often used as an embedded HTTP server. So why don’t we use this trick and embed Jetty into our standalone app to serve XRebel UI.

Here’s our example application:

Just for the demonstration purposes, it executes an HTTP request every 3 seconds and reads the response. Quick and dirty.

To embed Jetty server we need is to add a dependency to Jetty container and initialize the server when the application starts. The required dependencies are jetty-server and jetty-servlet:

Then we can start Jetty by adding the following code snippet into the static initializer of the class:

To enable XRebel agent, you need to start the application with -javaagent VM argument pointing to the location of xrebel.jar. For instance:

-javaagent:/Users/anton/tools/xrebel/xrebel.jar -Dxrebel.traces.all=true

I also added -Dxrebel.traces.all=true VM property to enable tracing of non-HTTP activities by XRebel. Tracing of non-HTTP activities in XRebel is disabled by default, hence I need to add this parameter in order to see profiling data for the periodic tasks (if I wish).

Once I launch the application, it will boot up the embedded Jetty instance on port 8080. The standalone XRebel UI is deployed by the agent to /xrebel context. Hence, if we open http://localhost:8080/xrebel in the browser we will see the following:

As you can see, it is quite easy to use XRebel with the standalone apps with this little trick. Just start an embedded Jetty instance on some port and you will be able to see what is your application doing. Perhaps, you can spot a sneaky bug with it before it gets to production! :)

If you want to play with the example application, I have it at GitHub. Download XRebel and start the application with the appropriate VM arguments to enable the agent. It will be fun! :)

Thursday, June 1, 2017

Conferences I have visited in May'17

Riga DevDays

Riga DevDays - a perfect conference of an Estonian to visit: not too far away (45 minutes flight), nice city, very good event!

There, I have presented a talk about Java class reloading, which covers the different options for reloading Java classes and explains the fundamental differences of those.

GeeCON, Krakow

I have presented at GeeCON before. The vibe of the event is quite energising! :) I have presented a talk about TestContainers which seemed to spark a lot of the interest from the attendees. Almost a full room and a lot of questions after the talk. Looks like integration testing is in demand these days! & JEEConf, Kiev

The visit to Kiev (Kyiv) was super-productive. I've visited EMAP offices of the on-site presentation as well as a local JUG meetup just before the conference. Very good attendance: 100+ people came to the meetup. Interestingly enough, in Ukraine (as well as in Russia) people ask questions in an interesting way: they usually start the question with "What if ...". They are always curious to find the limitations of the technology, the approach, the method, etc - almost like trying to break things. I think this critical mindset is very helpful when you have to develop software these days.

At the JEEConf I have presented 3 talks: 2 on my own, and 1 with Anton Keks, helping to deliver the Kotlin Puzzlers talk. This was a very well organized conference: super-nice view in the center of Kiev, well crafted schedule with the interesting and useful talks, good athmosphere... I recommend :)

I had a pleasure to deliver a live coding session about Javassist, though I still have the slides just as a reference for those who attended the session. I don't find this talk to be very useful for the developers, however, attendees still find it interesting, so I'm puzzled with this a bit :) Here are the slides:

As for the Java class reloading talk, I had some time to update the content since Riga DevDays -- removed boring parts and added a few other things. Lots of "What if.." questions after the talk -- I love this crowd! :)

Sunday, January 22, 2017

Twitterfeed #4

Welcome to the fourth issue of my Twitterfeed. I'm still quite irregular on posting the links. But here are some interesting articles that I think are worth sharing.

News, announces and releases

Atlassian aquired Trello. OMG! I mean... happy for Trello founders. I just hope that the product would remain as good as it was.

Docker 1.13 was released. Using compose-files to deploy swarm mode services is really cool! The new monitoring and build improvements are handy. Also Docker is now AWS and Azure-ready, which is awesome!

Kotlin 1.1 beta was published with a number of interesting new features. I have mixed feelings, however. For instance, I really find type aliases an awesome feature, but the definition keyword, "typealias", feels too verbose. Just "alias" would have been much nicer.
Meanwhile, Kotlin support was announced for Spring 5. I think this is great - Kotlin suppot in the major frameworks will definitely help the adoption.

Is there anyone using Eclipse? [trollface] Buildship 2.0 for Eclipse is available, go grab it! :)

Resonating articles

RethinkDB: Why we failed. Probably the best post-mortem that I have ever read. You will notice a strange kvetch at first about the tough market and how noone wants to pay. But then reading forward the author honestly lists what was really wrong. Sad that it didn't take off, it was a great project.

The Dark Path - probably the most contradicting blog post I've read recently. Robert Martin takes his word on Swift and Kotlin. A lot of people, the proponents of strong typing, reacted to this blog post immediately. "Types are tests!", they said. However, I felt like Uncle Bob just wrote this articles to repeat his point about tests: "it doesn't matter if your programming language strongly typed or not, you should write tests". No one would disagree with this statement, I believe. However, the followup article was just strange: "I consider the static typing of Swift and Kotlin to have swung too far in the statically type-checked direction." OMG, really!? Did Robert see Scala or Haskell? Or Idris? IMO, Swift and Kotlin hit the sweet spot in regards to type system that would actually _help_ the developers without getting in the way. Quite a disappointing read, I have to say..

Java 9

JDK 9 is feature complete. Those are great news. Now, it would be nice to see how will the ecosystem survive with all the issues related to reflective access. Workarounds exist, but there should be a proper solution without such hacks. Jigsaw caused a lot of concerns here and there but the bet is that in the long run, the benefits will outweigh the inconveniences.


The JVM is not that heavy
15 tricks for every web dev
Synchronized decorators
Code review as a gateway
How to build a minimal JVM container with Docker and Alpine Linux
Lagom, the monolith killer
Reactive Streams and the weird case of backpressure
Closures don’t mean mutability.
How do I keep my git fork up to date?

Predictions for 2017

Since it is the beginning of 2017, it is trendy to make predictions for the trends of the upcoming year. Here are some prediction by the industry thought leaders:

Adam Bien’s 2017 predictions
Simon Ritter’s 2017 predictions
Ted Neward’s 2017 predictions

Disqus for Code Impossible