JCON 2021

Is it viable to implement complex applications without any JavaScript frameworks? After introducing the basics at JCON 2020, now it's time to focus on state management, component communication, routing, structure, unidirectional data flow, and structure for plain Web Components, plain CSS and plain, modern JavaScript. Your questions are highly appreciated.

Blockchain technology is often dismissed as a useless overhyped pyramid-scheme by big parts of the IT community. At the same time, people tend to throw Bitcoin, cryptocurrency, NFTs, Ethereum and Proof-of-Work into the same bag, which leads to false assumptions about applicability and drawbacks of blockchain technology. I don’t want to convert anyone into a blockchain zealot, but I’d like to capture your curiosity as engineers and computer scientists. Ethereum is an exciting technology and a technological experiment on a world scale. It provides us with a global singleton computer, that can’t be stopped or censored by third parties, while at the same time being ubiquitous. It is natively object-oriented and open by design all the while being accessible by using traditional programming languages and constructs. It provides us with a new class of applications, decentralized apps (Dapps). While I don’t think what you learn in this talk will be something you will directly apply in your day to day work, I hope it will inspire you to see things that might be. To say it in the words of Alan Turing, the father of modern computer science and artificial intelligence: “We can only see a short distance ahead, but we can see plenty there that needs to be done.”

It all started with a small project to pass the time during The Great Quarantine of 2020. I bought some chiles from the local farmer’s market (with proper face coverings and social distancing, of course), fermented my first batch of hot sauce, and shared it with a few friends around the globe. I had no idea the sauce would be such a massive success, so I resolved to build on that triumph in 2021. But this time, I knew that I would have to start from the very beginning and grow the chiles myself. Of course, this presented the wonderful opportunity to combine two of my life’s greatest passions - the culinary arts and technology - to ensure that my growth operation was the ultimate success. Join me in this session where I show you how I used a microcontroller, some sensors and the cloud to monitor and automate the germination and maturation of this year’s crop.

Single page applications (SPA) have become the for web application development. Angular, React, Vue.js and Ember.js are the best known representatives from this category of web frameworks. But does this client architecture fit every application? Or are there alternatives that may fit better and are less complex to develop? In the first part of the talk, the differences between SPAs and classic, server-side approaches are explained and the advantages and disadvantages are discussed. The second part reports on a current customer project in which the front end of a large ERP system had to be replaced by a modern web front end. The chosen framework is Vaadin Flow, a server-side web framework that makes development of web applications entirely in Java possible. First, the new architecture of Vaadin Flow, which is no longer based on GWT but on web components, is explained. Then it will be shown how configurable, form-based and data-centric web applications can be implemented very efficiently by using jOOQ as a database access layer.

Race conditions are not an issue of the past nor a scenario that people can find themself in only when deciding to develop a multithreading architecture. In our day-to-day programming sessions, we probably deal with multithreading more than one may think. What about that simple Controller you wrote with just few lines of code? Could it be leaking customer data? MVC Controllers methods are, by default, executed in a multithreaded environment where it is crucial to understand when a variable will be accessed and how to synchronize access to shared resources. Failing to do so can have an impact on the security of your application and lead to issues that are difficult to reproduce. Here we will demonstrate a race condition on MVC controller and j2EE Servlet as introduction to a live coding session; we will discuss strategies that can be applied to mitigate the issue and conclude with a summary of how these methods can have an impact on the application’s performance and some other possible alternative

HTML spielt in modernen Web Anwendungen nur die zweite Geige. JavaScript Frameworks wie Angular oder React spielen die erste. Aber muss das so sein? Mit Turbo (https://turbo.hotwire.dev/) stellt Basecamp (um Rails Gründer David Heinemeier Hansson) einen alternativen Ansatz vor, um moderne Web Anwendungen mit plain HTML zu entwickeln. Das Grundprinzip von Turbo: Über die Leitung geht nur HTML, gerendert wird auf dem Server. An einem praktischen Beispiel lernt Ihr mit Turbo eine moderne Web Anwendung zu bauen, nur mit HTML. Das Beispiel geht von Login und Navigation mit Turbo Drive bis zum Formular mit Turbo Streams. Ihr sollt in der Lage sein zu beurteilen, ob der Turbo Ansatz für Web Anwendungen mit plain HTML für Euch das richtige ist. Vielleicht steckt dann bald auch Turbo Power in Eurer neuen oder alten Web App.

When you inspect YouTube’s code in the browser, you’ll see HTML elements such as ytd-thumbnail and ytd-player. These elements are called Web Components and you’ll find them not only on YouTube but websites such as GitHub and Google Patents. In this talk, you’ll learn what Web Components are, what the three standards that enable them are, how to code them in vanilla JavaScript, and how to use them from Java without having to use HTML or JavaScript. All this in a talk with more code than slides!

Web Components versprechen leichtgewichtige, frameworkunabhängige UI Komponenten. Doch was wird aus diesem Versprechen in der Praxis? Für welche Teams und Projekte sind Web Components die richtige Wahl und welchen Einfluss haben sie auf die Entwicklung? Wie entwickelt man eine eigene Komponentenbibliothek? Patrick Schröer und Christian Siebmanns berichten aus verschiedenen Projekten und geben Einblick in die Vorteile, Herausforderungen und Erfahrungen aus der Entwicklung von Web Components.

You've heard about React, the user interface library developed by Facebook? And you're wondering how to use it beyond the “Hello, World” stage? Then this talk is for you! Join me in an action-packed session full of live code examples where we'll discover how you can use React to build the hottest web applications while keeping your head cool. When you leave the room, you'll know enough to build real-world web applications!

Single Page Applikationen mit Frameworks wie React, Angular oder Vue.js ermöglichen dank umfangreicher Komponenten Bibliotheken wie Fluent UI oder Material Design ansprechende und komplexe Oberflächen zu erstellen. Allerdings erhört die Verwendung solcher Frameworks die Komplexität bei Webanwendungen erheblich. Typischerweise wird serverseitig eine REST-Schnittstelle implementiert. Dadurch wird es erforderlich den Zustand der Anwendung auf dem Server und im Client konsistent zu halten, was die Komplexität weiter erhöht. Wenn dann auch noch die Webseite serverseitig gerendert werden soll, führt das meistens noch zu einem zusätzlichen NodeJs-Server.
Gibt es noch andere Optionen, die schnelle Interaktion von SPA mit serverseitigem rendern der Webseiten zu kombinieren? Schaut man sich zum Beispiel, wie schnell Amazon die Produktlisten beim Stöbern aktualisiert, stellt man fest, dass dort fertig erzeugtes HTML via AJAX geladen und in den bestehenden DOM eingebaut wird. Die E-Mail-Anwendung HEY von Basecamp geht noch ein Schritt weiter und sendet fertig erzeugtes HTML über WebSockets.
Ich möchte zeigen, wie man mit "HTML over the Wire" moderne Web-Applikationen bauen kann. Dabei nutzen wir die Bibliotheken Turbo und Stimulus.

Security in Jakarta EE has long been under used and under specified. Existing specifications ranged from overly complex to non-existent. The result was few people used security standards. Java EE 8 changed that with JSR 375. Its evolution Jakarta Security facilitates portable application security integrated with container security. Allowing applications to treat authentication mechanisms like OAuth or OpenID Connect same as built-in container mechanisms like FORM or container-based access to a URL and features like @RolesAllowed and isUserInRole automatically work as expected. It depends on CDI, and lower level SPIs Jakarta Authentication and Jakarta Authorization. Jakarta Authorization defines an SPI for authorization based security checking if a subject has given permissions and algorithms to transform security constraints for containers including Servlets or Enterprise Beans into them. Jakarta Authentication defines an SPI for authentication that interacts with a container’s environment to obtain the caller’s credentials, validate them and pass an authenticated identity (e.g. name, groups,...) to the container. This hands-on session is intended to get attendees up to speed with the state of Jakarta Security specs, demonstrate compatible implementations like Soteria, Exousia and others including Eclipse Glassfish or Tomcat. We will ask the audience for their opinion and thoughts what else they would like to see in the Security specs with Jakarta EE 10 and beyond.

In the presentation, you'll learn how to build a full-stack web app step-by-step from scratch. Vaadin Fusion is a new unique web framework designed for Java backends. It combines a Spring Boot backend with a TypeScript-based LitElement frontend. It includes 40+ customizable UI components, type-safe server communication, and preconfigured build tooling–everything you need for productive and enjoyable development.