java.lang.NoClassDefFoundError: Could not initialize class org.springframework.web.reactive.function.client.DefaultExchangeStrategiesBuilder

Question

I am trying to use spring WebClient wc = WebClient.create(); in a non-Spring application, but it looks like DefaultExchangeStrategiesBuilder.DEFAULT_EXCHANGE_STRATEGIES returns null

causing error:
java.lang.NoClassDefFoundError: Could not initialize class org.springframework.web.reactive.function.client.DefaultExchangeStrategiesBuilder
    at org.springframework.web.reactive.function.client.ExchangeStrategies.withDefaults(ExchangeStrategies.java:67)
    at org.springframework.web.reactive.function.client.DefaultWebClientBuilder.initExchangeStrategies(DefaultWebClientBuilder.java:302)
    at org.springframework.web.reactive.function.client.DefaultWebClientBuilder.build(DefaultWebClientBuilder.java:269)
    at org.springframework.web.reactive.function.client.WebClient.create(WebClient.java:144)

I have added to my POM:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webflux</artifactId>
    <version>2.6.5</version>
</dependency>

Answer 1

If your application is not a Spring Boot application and does not apply Spring Boot's dependency management, you should not use Spring Boot's starters.

Instead you should use Spring Framework's spring-webflux dependency directly, as well as a client library of your choice, like Reactor Netty, Jetty client, Apache HttpComponents...

You should also ensure that the Spring Framework BOM is applied to your project to avoid an incompatible mix of versions in your application:

<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-framework-bom</artifactId>
  <version>...</version>
  <type>pom</type>
</dependency>