sce.getServletContext().setAttribute("Config", new Config());

ServletContext crossContext 
                = sce.getServletContext().getContext("/app1");
Config config = (Config) crossContext.getAttribute("Config");

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </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>

        Object result = crossContext.getAttribute("Config");
        
        System.out.println("Object classloader: " + result.getClass().getClassLoader());
        System.out.println("Target class classloader: " + Config.class.getClassLoader());
        
        if(result.getClass().getClassLoader() != Config.class.getClassLoader()) {
            System.out.println("Different classloaders detected!");
        }