启动Spring Vaadin Web应用时spring-boot-maven-plugin报错

Hey there, let's work through this error you're facing when running spring-boot:run! That NoClassDefFoundError typically points to a classpath issue—either a missing dependency, version mismatch, or cached build artifact causing problems. Here are the steps I'd take to fix it:

• Update your Spring Boot version
  Spring Boot 2.0.0.RELEASE is quite outdated (it's from 2018), and it might not be compatible with the Vaadin version the tutorial uses. Try upgrading to a more recent, stable release that works with your Vaadin setup. For example, if you're using Vaadin 14+, Spring Boot 2.7.x is a solid choice. Update the parent version in your pom.xml:

  <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.7.15</version>
      <relativePath/>
  </parent>
  

• Validate your Vaadin dependencies
  Make sure you've got the correct Vaadin starter in your pom.xml—this ensures all required Vaadin and Spring Boot integrations are included:

  <dependency>
      <groupId>com.vaadin</groupId>
      <artifactId>vaadin-spring-boot-starter</artifactId>
  </dependency>
  

  Double-check that your Vaadin version aligns with your chosen Spring Boot version (older Vaadin releases won't work with newer Spring Boot, and vice versa).

• Clean and rebuild your project
  Cached dependencies or build artifacts often cause weird classpath issues. Run these commands to wipe old builds and refresh dependencies:

  mvn clean
  mvn install
  

  Then try running mvn spring-boot:run again.

• Check for conflicting dependencies
  Use the mvn dependency:tree command to generate a list of all your project's dependencies. Look for multiple versions of Spring Boot core libraries (like spring-boot-starter or spring-boot-autoconfigure)—conflicts here can break the classpath. If you find mismatches, you may need to exclude conflicting dependencies from your pom or align versions.

• Verify your CommandLineRunner implementation
  If you've added a custom class that implements CommandLineRunner, make sure it's properly annotated with @Component (or that your main application class implements it and is annotated with @SpringBootApplication). Also, double-check your imports—typos here can lead to the JVM looking for the wrong class.

内容的提问来源于stack exchange，提问作者ShorKy