SpringBoot Jsp 404

场景

仿照SpringBoot官方spring-boot-sample-web-jsp，在IDEA中建立了同样的项目。直接在IDEA中启动项目，出现以下现象：

1. 数据接口可以正常访问；
2. 视图不能被解析，即访问页面时，会出现404客户端异常；

如图所示：

数据

视图

相关配置

application.yml

mvc:
    view:
      prefix: /WEB-INF/pages/
      suffix: .jsp

HomeController

@Controller
public class HomeController {

    /**
     * 首页
     */
    @GetMapping("/")
    public String index(){
        return "hello";
    }
}

解决办法

1. 使用mvn spring-boot:run命令行启动
2. 在pom文件中增加内置tomcat:

    org.apache.tomcat.embed
    tomcat-embed-jasper
    provided

原因

With Jetty and Tomcat, it should work if you use war packaging. An executable war will work when launched with java -jar, and will also be deployable to any standard container. JSPs are not supported when using an executable jar.

大致意思： 如果将你的程序打包成war包，在jetty、Tomcat和使用java -jar 命令时，JSP会起作用。但是如果是作为一个可执行的jar包的话，JSP不受支持。

Do not use the src/main/webapp directory if your application is packaged as a jar. Although this directory is a common standard, it works only with war packaging, and it is silently ignored by most build tools if you generate a jar.

大致意思：如果您的应用程序打包为jar，那么不要使用src/main/webapp目录。虽然这个目录是一个通用标准，但它只与war打包一起工作，并且如果您生成一个jar，它会被大多数构建工具默默忽略。代码如下：

protected boolean isInvalidPath(String path) {
        if (logger.isTraceEnabled()) {
            logger.trace("Applying \"invalid path\" checks to path: " + path);
        }

        if (!path.contains("WEB-INF") && !path.contains("META-INF")) {
            if (path.contains(":/")) {
                String relativePath = path.charAt(0) == '/' ? path.substring(1) : path;
                if (ResourceUtils.isUrl(relativePath) || relativePath.startsWith("url:")) {
                    if (logger.isTraceEnabled()) {
                        logger.trace("Path represents URL or has \"url:\" prefix.");
                    }

                    return true;
                }
            }

            if (path.contains("..")) {
                path = StringUtils.cleanPath(path);
                if (path.contains("../")) {
                    if (logger.isTraceEnabled()) {
                        logger.trace("Path contains \"../\" after call to StringUtils#cleanPath.");
                    }

                    return true;
                }
            }

            return false;
        } else {
            if (logger.isTraceEnabled()) {
                logger.trace("Path contains \"WEB-INF\" or \"META-INF\".");
            }

            return true;
        }
    }

代码中显示WEB-INF和META-INF为非法路径

另外，官方也说了尽量避免使用JSP。

If possible, JSPs should be avoided. There are several known limitations when using them with embedded servlet containers.