我将现有的（并且正常运行的！）Vaadin 应用程序从使用 v18.0.2 升级到 v21.0.4。使用新版本，服务器端应用程序照常启动，初始化正常，第一个请求触发前端编译（似乎也正常工作，至少日志没有显示任何异常或错误），但 UI 只是挂起并且无法加载（页面顶部有一个细长的蓝色进度条，它很快达到宽度的约 50%，然后它变得越来越慢，然后在屏幕宽度的约 90% 时停止运行）。

我完全不知道应该朝哪个方向检查或分析这个问题。任何建议或提示这里可能出错的地方都将不胜感激！

如果我应该附加任何配置或日志详细信息以帮助分析此问题，请告诉我！

稍后补充： 我在此处附加了我的 vaadin_dance.cmd ：

@echo off

:package_entries
set fn=package.json
echo Step 1: Going to remove unsupported Vaadin v19+ entries from %fn%:
pause
rem let user see what we do:
@echo on
type %fn%   | findstr /V /C:"@vaadin/application-theme-plugin" > %fn%_1
type %fn%_1 | findstr /V /C:"@vaadin/stats-plugin"             > %fn%_2
type %fn%_2 | findstr /V /C:"@vaadin/theme-live-reload-plugin" > %fn%_3
type %fn%_3 | findstr /V /C:"@vaadin/theme-loader"             > %fn%_4
rem remove an already existing backup - just in case (if there were one the cp below won't work)
rm %fn%~
rem rename back to original and keep a backup:
cp -b -f %fn%_4 %fn%
rem delete the temp. files":
rm %fn%_?
@echo off
echo unsupported Vaadin v19+ entries removed from %fn%

:local_stuff
echo Step 2: Going to remove project local stuff:
pause
rem let user see what we do:
@echo on
rmdir /S /Q .\target
rmdir /S /Q .\node_modules
rmdir /S /Q .\frontend\generated
rm package.json
rm package-lock.json
rm pnpm-lock.yaml
rm pnpmfile.js
rm tsconfig.json
rm types.d.ts
rm webpack.config.js
rm webpack.generated.js
@echo off
echo project local vaadin-generated stuff removed.

:global_stuff
echo Step 3: Going to remove global stuff: removing pnpm stuff
pause
rem let user see what we do:
@echo on
rm -r -f %USERPROFILE%\.pnpm-debug.log
rm -r -f %USERPROFILE%\.pnpm-state.json
rmdir /S /Q %USERPROFILE%\.vaadin
rmdir /S /Q %USERPROFILE%\.pnpm-store
rem just in case - I encountered them here, too:
rmdir /S /Q D:\.pnpm-store
rmdir /S /Q U:\.pnpm-store
@echo off
echo global vaadin-installed stuff removed.
rem clear (and preload) default repository:

:repo_stuff
echo Step 4: Going to empty m2repository!
pause
rem let user see what we do:
@echo on
rem strange enough I again and again got "access denied" on certain .jars ||-(  So we first take ownership...
takeown /R /F %USERPROFILE%\.m2\m2repository
rem ... before removing the stuff:
rm -r -f %USERPROFILE%\.m2\m2repository\*
@echo off
echo m2repository cleaned.
echo.
pause

上述 .cmd 文件的过程是这样的，我首先运行步骤 1，然后停止它并尝试重建（在不同的 cmd 窗口中）。如果这不起作用，我会从头重新启动它并运行步骤 1 和 2，然后我停止并尝试重建，等等。最多在步骤 1、2、3 和 4 之后，我（至少到目前为止）总是能够重建和执行我的应用程序。至少在使用 v18.0.3 构建或恢复到 v18.0.3 时是这样。使用 v21.x 我到目前为止还没有成功。 :-(

第二个附录包含控制台输出：

应用程序启动正常（即没有任何错误消息（直到我看到“Tomcat 已在端口上启动：...”

此时，我将浏览器指向触发 DispatcherServlet 调度的端口。该页面从未加载，浏览器超时，但控制台上没有任何错误消息或任何提示问题类型或原因的内容：

...
2021-12-17 19:36:03,459 INFO  [main] org.springframework.boot.web.embedded.tomcat.TomcatWebServer: Tomcat started on port(s): 8085 (http) with context path ''
2021-12-17 19:36:23,678 INFO  [http-nio-8085-exec-1] org.apache.juli.logging.DirectJDKLog: Initializing Spring DispatcherServlet 'dispatcherServlet'
2021-12-17 19:36:23,682 INFO  [http-nio-8085-exec-1] org.springframework.web.servlet.FrameworkServlet: Initializing Servlet 'dispatcherServlet'
2021-12-17 19:36:23,689 INFO  [http-nio-8085-exec-1] org.springframework.web.servlet.FrameworkServlet: Completed initialization in 2 ms
2021-12-17 19:36:26,103 WARN  [http-nio-8085-exec-1] org.apache.juli.logging.DirectJDKLog: Creation of SecureRandom instance for session ID generation using [SHA1PRNG] took [2,172] milliseconds.
2021-12-17 19:36:26,103 WARN  [http-nio-8085-exec-3] org.apache.juli.logging.DirectJDKLog: Creation of SecureRandom instance for session ID generation using [SHA1PRNG] took [1,457] milliseconds.
2021-12-17 19:36:26,179 INFO  [http-nio-8085-exec-4] com.vaadin.flow.spring.SpringInstantiator: The number of beans implementing 'I18NProvider' is 0. Cannot use Spring beans for I18N, falling back to the default behavior
<Console output stops here and browser times out>

不幸的是，这里似乎没有办法附加屏幕截图，所以我无法在此处提供 WebDeveloper 的网络选项卡的输出...

浏览器检查器控制台显示：

Fri Dec 17 2021 19:52:01 GMT+0100 (Central European Standard Time) Atmosphere: unload event vaadinPush-min.js:1:40213
Vaadin push loaded vaadinPush-min.js:1:44231
Failed to register/update a ServiceWorker for scope ‘http://localhost:8085/’: Bad Content-Type of ‘text/html’ received for script ‘sw-runtime-resources-precache.js’.  Must be a JavaScript MIME type.
Uncaught (in promise) TypeError: ServiceWorker script at http://localhost:8085/sw.js for scope http://localhost:8085/ threw an exception during script evaluation.
Path '/login' is not properly resolved due to an error. Resolution had failed on route: '(.*)' vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58:17000
Uncaught (in promise) TypeError: class heritage e is not an object or null
    to http://localhost:8085/VAADIN/build/vaadin-3-1a44b245d20aa3c33130.cache.js:1
    266 http://localhost:8085/VAADIN/build/vaadin-3-1a44b245d20aa3c33130.cache.js:765
    r http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:1
    promise callback*imports http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    flowInit http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    async*get action/< http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    Z http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    __resolveRoute http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    promise callback*__resolveRoute http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    resolveRoute http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    a http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    a http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    promise callback*a http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    resolve http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    promise callback*resolve http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    render http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    __onNavigationEvent http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    setRoutes http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    <anonymous> http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:58
    r http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:1
    <anonymous> http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:1
    <anonymous> http://localhost:8085/VAADIN/build/vaadin-bundle-aec7d8b0cb06e0cbb6bd.cache.js:1
vaadin-3-1a44b245d20aa3c33130.cache.js:1:153

​ 非 Vaadin 实习生应该如何解码这些内容并分析这里出了什么问题？