@Configuration

public class WebConfig implements WebMvcConfigurer {                                                            

       @Override

       public void addResourceHandlers(ResourceHandlerRegistry registry){

           registry.addResourceHandler("/ui/html/**").addResourceLocations("classpath:/ui/html/");              

       }                                                                                                        

}                                                                                                               

  <dependencies>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter</artifactId>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</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>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-web</artifactId>

            <version>5.2.0.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>com.google.code.gson</groupId>

            <artifactId>gson</artifactId>

            <version>2.8.6</version>

        </dependency>

    </dependencies>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>