java.lang does not contain a class called StringUtils. Several third-party libs do, such as Apache Commons Lang or the Spring framework. Make sure you have the relevant jar in your project classpath and import the correct class.

You are most likely mixing up Spring dependencies from different framework versions. StringUtils.matchesCharacter() method was introduced in Spring 5.2.9. It looks like you are using Spring Boot 2.3.5.RELEASE which depends on Spring 5.2.10 so you should be fine, however:

1. You are either deploying to a runtime environment that provides spring-boot-starter-web jar in different, lower version.

2. Or the dependency spring-boot-starter-web should not be marked as <scope>provided</scope> in your pom.xml because it's needed in the runtime.

You didn't put your entire pom.xml, but I guess that you forgot the dependency:

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.4</version>
</dependency>

You said that your project works inside Intellij, then you already have the common-lang3 in your computer.

I think the problem resides in the maven dependencies.

Try to execute: mvn clean install via command line in the root folder of your project.

You need to put your commons-lang3-3.4.jar in the classpath

Two links to help you:

https://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.html

Run a JAR file from the command line and specify classpath

I believe you're using org.springframework.util.StringUtils, which has no isEmpty().

There is, however, an isEmpty() in org.apache.commons.lang.StringUtils.

Ensure that you're using the correct StringUtils.

You need to import the org.apache.commons.lang package.