我正在使用Sping Boot 开发一个社区网站，当我尝试测试“注册”功能时，它显示此错误：

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.

Wed Aug 16 01:02:01 EDT 2023
There was an unexpected error (type=Internal Server Error, status=500).
org/apache/commons/lang3/StringUtils
java.lang.NoClassDefFoundError: org/apache/commons/lang3/StringUtils
    at com.nowcoder.community.service.UserService.register(UserService.java:48)
    at com.nowcoder.community.controller.LoginController.register(LoginController.java:26)

因为它提到了从“if（StringUtils.isBlank（user.getUsername（）”开始的第48行

public Map<String, Object> register(User user) {
        Map<String, Object> map = new HashMap<>();

        // Empty value
        if (user == null) {
            throw new IllegalArgumentException("User cannot be null!");
        }
        if (StringUtils.isBlank(user.getUsername())) {
            map.put("usernameMsg", "Username cannot be empty!");
            return map;
        }
        if (StringUtils.isBlank(user.getPassword())) {
            map.put("passwordMsg", "Password cannot be empty!");
            return map;
        }
        if (StringUtils.isBlank(user.getEmail())) {
            map.put("emailMsg", "Email cannot be empty!");
            return map;
        }

我在pom.xml文件中添加了commons-lang 3

<dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.13.0</version>
        </dependency>

我用的是IntelliJ，不知道是不是相关的。我已经导入了import org.apache.commons.lang3.StringUtils;