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Chapter 1 – Introduction 1.1 Motivation: Real-time communication without polling In modern applications, it is often necessary to provide new information to the client as quickly as possible. Classic polling, i.e. regularly querying a REST endpoint, is inefficient: it generates unnecessary network traffic and puts a load on both server and client, as requests continue even when there is no new data.

Reactive streams address a fundamental problem of modern systems: Producers (sensors, services, user events) deliver data at an unpredictable rate, while consumers (persistence, UI, analytics) can only process data at a limited speed. Without a flow control model , backlogs, storage pressure, and ultimately outages occur. With Java, java.util.concurrent.Flow provides a minimalist API that standardises this problem: Publisher → Processor → Subscriber,

1. Introduction 1.1 Motivation: Event-driven updating without polling In classic web applications, the pull principle still dominates: Clients repeatedly make requests to the server to detect changes. This polling is simple, but it leads to unnecessary load on the server and network side, especially if the data stock changes only sporadically. Server-Sent Events (SSE) is a standardised procedure that allows the server to signal changes to connected clients actively.

Password security is an often underestimated but critical topic in software development. Databases containing millions of user logins are repeatedly compromised – and shockingly, often, it tu…

1. Introduction and objectives The first two parts of this series established the theoretical and practical foundations of a URL shortener in pure Java. We discussed the semantic classification of …

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1. Introduction Why REST integration in Vaadin applications should not be an afterthought In modern web applications, communication with external services is no longer a special function, but an in…

YouTube video by Sven Ruppert - german

A URL shortener seems harmless – but if implemented incorrectly, it opens the door to phishing, enumeration, and data leakage. In this first part, I’ll explore the theoretical and security-re…

Ein tiefer Blick in Java’s HashMap-Fallen – visuell demonstriert mit Vaadin Flow Die stille Gefahr in der Standardbibliothek…

A deep look into Java’s HashMap traps – visually demonstrated with Vaadin Flow. The silent danger in the standard library The use of HashMap and HashSet is a common practice in everyday Java develo…

Vaadin Flow ist ein leistungsstarkes Framework zur Erstellung moderner Webanwendungen in Java, bei denen die gesamte UI-Logik serverseitig…

Vaadin Flow is a robust framework for building modern web applications in Java, where all UI logic is implemented on the server side. In this blog post, we’ll make a simple file management ap…

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What is the Java Instrumentation API? The Java Instrumentation API is part of the java.lang.instrument package and allows you to change or analyse class bytecode at runtime. It is particularly inte…

Sometimes it’s not enough for something to work – it has to work under load. In modern applications that process large amounts of data, the Streams API in Java provides developers with …

1. Getting started – trust in everyday internet life Anyone who enters a web address like “www.example.de” into the browser expects a familiar website to appear within seconds. Whether in the home …

The Java Cryptography Architecture (JCA) is an essential framework within the Java platform that provides developers with a flexible and extensible interface for cryptographic operations. It is a c…

Since version 8, Java has introduced an elegant, functional approach to processing data sets with the Streams API. The terminal operation collect(…) represents the bridge from the stream to a…