Spring boot + JSP + @Controller注解返回页面的时候，如果提示下面的错误：

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Mon Oct 17 18:12:22 CST 2022
There was an unexpected error (type=Not Found, status=404).
No message available

那是因为缺少以下依赖包：

<!-- jsp的整合依赖 -->
<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-jasper</artifactId>
</dependency>

记得Maven  Sync 一下项目，否则还是不生效的。

@Controller

public class TestController {
    @RequestMapping(value="/")
    public String index(Model model, HttpServletResponse response) {
        model.addAttribute("name","this is ok");
        return "index";
    }
}

当然，不要忘记在 /src/main/webapp/WEB-INF/jsp目录下，放上你的jsp文件。