Error creating bean with name 'undertowServletWebServerFactory' when deploying Spring Boot application in JBoss EAP 7.1.0 - spring-boot

Question

I am trying to deploy a Spring Boot application in JBoss EAP 7.1.0. The Spring Boot application internally calls Apache Camel route and sends message to a JMS queue (provided by ActiveMQ Artemis embedded in JBoss EAP 7.1.0). The pom.xml is as under:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.3.3.RELEASE</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
<groupId>com.demo</groupId>
<artifactId>SpringMQDemo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>SpringMQDemo</name>
<description>MQ Demo</description>
<packaging>war</packaging>
<properties>
<java.version>1.8</java.version>
<maven.test.skip>true</maven.test.skip>
</properties>
<dependencies>
<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>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-spring-boot-starter</artifactId>
<version>2.25.1</version>
</dependency>
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-jms</artifactId>
<version>2.25.1</version>
</dependency>
<dependency>
<groupId>org.wildfly</groupId>
<artifactId>wildfly-naming-client</artifactId>
<version>1.0.7.Final</version>
</dependency>
<dependency>
<groupId>org.apache.activemq</groupId>
<artifactId>artemis-jms-client</artifactId>
</dependency>
<dependency>
<groupId>javax.json</groupId>
<artifactId>javax.json-api</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
While trying to deploy the war file in JBoss EAP 7.1.0, the below exception is thrown:
Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2020-09-21 23:54:16,719 ERROR [org.springframework.boot.SpringApplication] (ServerService Thread Pool -- 122) Application run failed: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'undertowServletWebServerFactory' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/ServletWebServerFactoryConfiguration$EmbeddedUndertow.class]: Initialization of bean failed; nested exception is java.lang.LinkageError: loader constraint violation: when resolving field "MAX_HEADER_SIZE" the class loader (instance of org/jboss/modules/ModuleClassLoader) of the referring class, io/undertow/UndertowOptions, and the class loader (instance of org/jboss/modules/ModuleClassLoader) for the field's resolved type, org/xnio/Option, have different Class objects for that type
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:602)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$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.web.servlet.support.SpringBootServletInitializer.run(SpringBootServletInitializer.java:173)
at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.createRootApplicationContext(SpringBootServletInitializer.java:153)
at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.onStartup(SpringBootServletInitializer.java:95)
at org.springframework.web.SpringServletContainerInitializer.onStartup(SpringServletContainerInitializer.java:172)
at io.undertow.servlet.core.DeploymentManagerImpl$1.call(DeploymentManagerImpl.java:192)
at io.undertow.servlet.core.DeploymentManagerImpl$1.call(DeploymentManagerImpl.java:174)
at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:42)
at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
at org.wildfly.extension.undertow.security.SecurityContextThreadSetupAction.lambda$create$0(SecurityContextThreadSetupAction.java:105)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
at io.undertow.servlet.core.DeploymentManagerImpl.deploy(DeploymentManagerImpl.java:239)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentService.startContext(UndertowDeploymentService.java:99)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentService$1.run(UndertowDeploymentService.java:81)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
at org.jboss.threads.JBossThread.run(JBossThread.java:320)
Caused by: java.lang.LinkageError: loader constraint violation: when resolving field "MAX_HEADER_SIZE" the class loader (instance of org/jboss/modules/ModuleClassLoader) of the referring class, io/undertow/UndertowOptions, and the class loader (instance of org/jboss/modules/ModuleClassLoader) for the field's resolved type, org/xnio/Option, have different Class objects for that type
at org.springframework.boot.autoconfigure.web.embedded.UndertowWebServerFactoryCustomizer.customize(UndertowWebServerFactoryCustomizer.java:81)
at org.springframework.boot.autoconfigure.web.embedded.UndertowWebServerFactoryCustomizer.customize(UndertowWebServerFactoryCustomizer.java:59)
at org.springframework.boot.web.server.WebServerFactoryCustomizerBeanPostProcessor.lambda$postProcessBeforeInitialization$0(WebServerFactoryCustomizerBeanPostProcessor.java:72)
at org.springframework.boot.util.LambdaSafe$Callbacks.lambda$null$0(LambdaSafe.java:287)
at org.springframework.boot.util.LambdaSafe$LambdaSafeCallback.invoke(LambdaSafe.java:159)
at org.springframework.boot.util.LambdaSafe$Callbacks.lambda$invoke$1(LambdaSafe.java:286)
at java.util.ArrayList.forEach(ArrayList.java:1249)
at java.util.Collections$UnmodifiableCollection.forEach(Collections.java:1080)
at org.springframework.boot.util.LambdaSafe$Callbacks.invoke(LambdaSafe.java:286)
at org.springframework.boot.web.server.WebServerFactoryCustomizerBeanPostProcessor.postProcessBeforeInitialization(WebServerFactoryCustomizerBeanPostProcessor.java:72)
at org.springframework.boot.web.server.WebServerFactoryCustomizerBeanPostProcessor.postProcessBeforeInitialization(WebServerFactoryCustomizerBeanPostProcessor.java:58)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:415)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1786)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:594)
... 35 more
The Spring Boot undertow dependency is not present in classpath and not added in pom.xml either. So I am not getting from where the undertow is being picked. Please help.

Answer 1

Undertow is JBoss EAP's servlet container so that will be where its classes are coming from. The LinkageError suggests a bug in JBoss to me but you may be able to work around it.
The class that's triggering the bug is Spring Boot's UndertowWebServerFactoryCustomizer. It's configured by some auto-configuration that's only needed when you're using an embedded web server. You can disable it by adding the following to your application.properties:
spring.autoconfigure.exclude=org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration