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I’m an independent IT consultant and entrepreneur in the Internet and software business. I’m interested in design, enterprise applications, web apps and SaaS products. I design and develop business solutions and applications. I help companies in terms of software quality and knowledge transfer, e.g. with Angular and Spring Boot.

REST next level: Crafting domain-driven web APIs by Julien Topçu @ Spring I/O 2023

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Action Jackson! Effective JSON processing in Spring Boot Applications by Joris Kuipers @ Spring I/O 2023

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JSON Visualization With JSON Crack

JSON Crack is a JSON visualization solution that allows to generated ad-hoc graph visualizations for your JSON data. While one of the huge advantages of JSON over other data formats certainly is that it's human-readable, more complex JSON documents containing linked data structures can become unwieldy and difficult to understand - at a cursory glimpse, at least. Such situations is where a tool like JSON Crack for visualizing data can come handy. Read more

Problem Spring Web: A Library for Handling Problems in Spring Web MVC

Problem Spring Web is an implementation of the proposed application/problem+json HTTP API problem details response for Spring Web (im both its MVC and WebFlux flavours). Error responses should be a first-class citizen when it comes to providing REST APIs. These responses often are generated in an ad-hoc, non-standardised fashion, which not only makes handling such responses more difficult and tedious in client applications but also makes for less maintainable software in the back-end software providing the API. Problem Spring Web attempts to ... Read more

Documenting REST APIs Provided by Express Applications

swagger-jsdoc is an NPM library that allows us to generate an OpenAPI specification for REST APIs provided by an Express application. swagger-jsdoc consumes YAML-formatted OpenAPI specification segments within JSDoc comments annotated with the @openapi annotation and turns those into a comprehensive OpenAPI specification for our API. This specification, in turn, can for example be used for automatically having a Swagger UI documentation page created for our REST APIs (using Swagger UI Express, for instance). While annotating Express routes with syntactically and semantically correct OpenAPI ... Read more

CORS: What It Is and How It Works

Expanding on last week's article on best practices for REST API Design I'd like to point to a specific aspect working REST APIs frequently entails: A browser security feature called "Cross-Origin Resource Sharing (CORS)". This feature allows you to define which resources provided by a web application are supposed to be accessible from which origin, which in turn typically is comprised of protocol, host / domain name and port. This website's origin for example is (port 80 is the default port ... Read more

REST API Design: Best Practices

It's probably safe to say that REST (REpresentational State Transfer - originally described by Roy Fielding) is the most widely used architectural pattern when it comes to APIs in web application contexts. From statelessness, to self-descriptive messages, and hypermedia as the engine of application state (HATEOAS) REST comes with quite a few principles, constraints, patterns, and flavours, not all of which are used or applied consistently with each REST API. REST often is a rather loosely-applied architectural pattern or a continuum, on ... Read more

The Richardson Maturity Model for REST APIs

On his website about software design patterns Martin Fowler provides an in-depth explanation of the Richardson Maturity Model for HTTP-based REST APIs by Leonard Richardson. According to that model REST APIs come in 4 levels of sophistication: Level 0, aka the "Everything is a POST request" model for example propagated by SOAP. This is basically tantamount to remote procedure invocation. Level 1 - Resources: Every resource is accessed through its own canonical URL. Level 2 - HTTP Verbs: Verbs such as GET, PUT, PATCH and ... Read more

JSON Web Tokens: Downsides, Best Practices and Secure and Robust Alternatives

JSON Web Tokens (JWTs) nowadays are commonly used for transmitting authentication data in web applications, especially those exhibiting the widespread client-server architecture where you have a fat client / single-page application written in JavaScript as a front-end and a back-end server providing REST endpoints for use by that front-end client. However, while common there are good arguments against this practice. In a nutshell, JWT often are used for storing session data such user authorization and authentication information although they aren't particularly well-suited to ... Read more

Jess Frazelle: “For the Love of Pipes”

Somewhat recently, Jess Frazelle wrote about her love of UNIX pipes, a sentiment I wholeheartedly share, to the extent that I think web apps should behave more like Unix programs by making data readily available via APIs so other applications can easily process that data. This, in a nutshell, is the Unix philosophy as stated by Doug McIlroy: Make each program do one thing well. To do a new job, build afresh rather than complicate old programs by adding new "features". Expect the output ... Read more
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