To allow requests against a Spring Boot REST API from a website it is necessary to configure CORS properly. In case you don’t know your client URLs you can allow all clients by adding a mapping like the following in your Kotlin project: This allows access to all endpoints from all origins via GET, POST …
CORS configuration for REST api accessed from browser Read More »
I found lots of samples for creating a redis testcontainer in Spring Boot tests. But none of them really worked. Below is a working base class with a sample. It is based on Spring Boot 3.1.2 and latest testcontainer version at time of writing (“org.testcontainers:testcontainers:1.18.3”). The testcontainer-redis versions were avoided on purpose because they were …
Using Spring Events can be very handy to decouple code. But have you ever tried creating generic events and then write a listener for them? Java or Kotlin themselves don’t prevent you from doing so but when you try receiving the events you will see that it doesn’t work. The reason for this is type …
With Spring Boot 3 some classes were deprecated and also the Keycloak adapter and the admin client stopped working in an application I am maintaining. In https://blog.coffeebeans.at/archives/1904 I already showed how to instantiate a WebClient which is the new way Spring wants us to call external APIs – not considering external libs like feign now. …
RestTemplate is dead and everybody should use WebClient now. That’s what you find everywhere so I had a look how to configure an instance of WebClient properly: This defines a bean genericWebClient with Spring Boot configured Jackson ObjectMapper instance. Here is also the code for the WebClientLoggerBuilder: This simply logs method, path and headers of …
While using Java and Kotlin with Spring Boot the following exception occurs and it’s quite hard to find how to fix it. The simple solution is to add the following top level config in your gradle file:
When upgrading to the latest tools and libraries in a Spring Boot application with OpenAPI code generator in place the OpenAPI Kotlin generator introduced jakarta.annotation:jakarta.annotation-api. But with this in place the application refused to start with something like org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat…Caused by: java.lang.IllegalStateException: …
java.lang.ClassNotFoundException: javax.annotation.PostConstruct Read More »
I created a github action config for detekt 1.19.0 based on Java 17 because the template from GitHub was using a much older version and also didn’t work for me.
I was trying to build a spring boot application based on spring spring-boot-starter-webflux which is based on kotlinx-coroutines-reactor. The API definition was done with OpenAPI-Generator with “kotlin-spring” generator and “spring-boot” library. Setting the configOptions useBeanValidation and reactive to true generates suspendable methods and uses webflux. And adding hibernate-validator allows to use bean validation for every …
ArrayIndexOutOfBounds with Kotlin coroutines and Hibernate-Validator Read More »
Using unmodifiable variables – so called values in Kotlin with keyword val – should be the default where possible but it’s not always practical to initialise all values within the constructor. Kotlin offers the option to use “by lazy”. With some common kinds of properties, even though you can implement them manually every time you …
Delegate value initialisation with “by lazy” in Kotlin Read More »