Replacing tomcat with undertow server for spring-boot-keycloak project results in IllegalStateException: No ServletContext set

Question

I'm trying to setup a simple spring-boot example project (keycloak tutorial) but I'm stuck at a startup error. The only thing that differs from the original config is that I want to use an undertow server instead of tomcat.

Running the main class without any changes is successfull (main class annotated with @SpringBootApplication) (mvn spring-boot:run after clean & install) (standard tomcat setup).

After the following changes in the pom, I'm getting an error:

java.lang.IllegalStateException: No ServletContext set

See below for details:

POM changes:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-undertow</artifactId>
</dependency>

instead of

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Spring boot startup error when using undertow:

12:48:55.077 [main] ERROR o.s.boot.SpringApplication - Application run failed org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'resourceHandlerMapping' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.web.servlet.HandlerMapping]: Factory method 'resourceHandlerMapping' threw exception; nested exception is java.lang.IllegalStateException: No ServletContext set at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:655) at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:635) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1336) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1176) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516) at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:897) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551) at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143) at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758) at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750) at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) at com.baeldung.keycloak.SpringBoot.main(SpringBoot.java:11) Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.web.servlet.HandlerMapping]: Factory method 'resourceHandlerMapping' threw exception; nested exception is java.lang.IllegalStateException: No ServletContext set at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:650) ... 20 common frames omitted Caused by: java.lang.IllegalStateException: No ServletContext set at org.springframework.util.Assert.state(Assert.java:76) at org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport.resourceHandlerMapping(WebMvcConfigurationSupport.java:534) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ... 21 common frames omitted

Spring-boot.version used is 2.3.3.RELEASE (as stated in a parent pom).

How can i get this to work with an undertow server?

Have you able to instantiate UndertowEmbeddedServletContainerFactory in your java config. Refer to baeldung.com/spring-boot-application-configuration — efire-net
That doesn't work (adding bean). It looks like outdated syntax as well, Ive tried with UndertowServletWebServerFactory instead of UndertowEmbeddedServletContainerFactory (does not compile). Unfortunately, the same errors appear. — fx772

fx772 fx772 · Accepted Answer · 2020-11-15T14:53:00

fixed

When the part as shown below is detached from the original SecurityConfig class, it works with undertow:

(new class)

@Configuration
public class KeycloakConfig {
  @Bean
  public KeycloakSpringBootConfigResolver KeycloakConfigResolver() {
    return new KeycloakSpringBootConfigResolver();
  }
}

Replacing tomcat with undertow server for spring-boot-keycloak project results in IllegalStateException: No ServletContext set

1 Answers