Upgrade from Spring Boot 2.7.2 to Spring Boot 3.0.0-SNAPSHOT: Caused by: java.lang.NoClassDefFoundError: javax/servlet/http/HttpServletRequest - spring

Question

Upgrade from Spring Boot 2.7.2 to Spring Boot 3.0.0-SNAPSHOT.
Error
Caused by: java.lang.NoClassDefFoundError: javax/servlet/http/HttpServletRequest
Full log https://gist.github.com/donhuvy/4eb218437077e58f996937ea255fb359
How to fix it?

Answer 1

This is happening, because in Spring Boot 3 they changed the version of Tomcat (if I'm not mistaken to 9) and in it all references to Javax were replaced by Jakarta. From what I saw your problem is with Swagger I managed to solve it using snapshot versions. In my case I used it for study and as the final release comes out in november 2022 it's not a big problem. I believe this here can help you. This is the project pom:
<?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>3.0.0-M2</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>br.com.erudio</groupId>
<artifactId>rest-with-spring-boot-and-java-erudio</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>rest-with-spring-boot-and-java-erudio</name>
<properties>
<java.version>18</java.version>
<dozer.version>6.4.0</dozer.version>
<springdoc.version>2.0.0-M1</springdoc.version>
<testcontainers.version>1.16.3</testcontainers.version>
<rest-assured.version>4.5.0</rest-assured.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.hateoas</groupId>
<artifactId>spring-hateoas</artifactId>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-xml</artifactId>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-yaml</artifactId>
</dependency>
<dependency>
<groupId>org.springdoc</groupId>
<artifactId>springdoc-openapi-starter-webmvc-ui</artifactId>
<version>${springdoc.version}</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<dependency>
<groupId>org.flywaydb</groupId>
<artifactId>flyway-core</artifactId>
</dependency>
<dependency>
<groupId>org.flywaydb</groupId>
<artifactId>flyway-mysql</artifactId>
</dependency>
<dependency>
<groupId>com.github.dozermapper</groupId>
<artifactId>dozer-core</artifactId>
<version>${dozer.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-core</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>io.rest-assured</groupId>
<artifactId>rest-assured</artifactId>
<version>${rest-assured.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.testcontainers</groupId>
<artifactId>mysql</artifactId>
<version>${testcontainers.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
<optional>true</optional>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>org.flywaydb</groupId>
<artifactId>flyway-maven-plugin</artifactId>
<configuration>
<url>jdbc:mysql://localhost:3306/rest_with_spring_boot_erudio?useTimezone=true&serverTimezone=UTC&useSSL=false</url>
<user>root</user>
<password>admin123</password>
</configuration>
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>${mysql.version}</version>
<exclusions>
<exclusion>
<artifactId>slf4j-api</artifactId>
<groupId>org.slf4j</groupId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
<repositories>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
</project>

Answer 2

It is simple, just replace javax in your import statement by jakarta.
for e.g.
old import statement:
import javax.servlet.http.HttpServletRequest;
new import statement:
import jakarta.servlet.http.HttpServletRequest;
Reason - Jump from Java EE to Jakarta EE9.