在我开始写代码之前，我试着通过appengine运行，结果发现了错误；

Server App Engine Standard at localhost failed to start.

我的控制台显示：

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.google.appengine.tools.development.StreamHandlerFactory (file:/C:/Users/boyla/AppData/Local/google/ct4j-cloud-sdk/LATEST/google-cloud-sdk/platform/google_appengine/google/appengine/tools/java/lib/impl/appengine-local-runtime.jar) to method java.net.URL.getURLStreamHandler(java.lang.String)
WARNING: Please consider reporting this to the maintainers of com.google.appengine.tools.development.StreamHandlerFactory
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
Nov 22, 2020 4:12:19 PM com.google.appengine.tools.development.SystemPropertiesManager setSystemProperties
INFO: Overwriting system property key 'java.util.logging.config.file', value 'C:\Users\boyla\AppData\Local\google\ct4j-cloud-sdk\LATEST\google-cloud-sdk\platform\google_appengine\google\appengine\tools\java\config\sdk\logging.properties' with value 'WEB-INF/logging.properties' from 'C:\Users\boyla\eclipse-workspace2\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\appenginedemo\WEB-INF\appengine-web.xml'
java.lang.NullPointerException
    at java.base/java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011)
    at java.base/java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:1006)
    at java.base/java.util.Properties.put(Properties.java:1334)
    at java.base/java.util.Collections$CheckedMap.put(Collections.java:3701)
    at com.google.appengine.tools.development.SharedMain.setTimeZone(SharedMain.java:183)
    at com.google.appengine.tools.development.SharedMain.postServerActions(SharedMain.java:152)
    at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:398)
    at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:45)
    at com.google.appengine.tools.development.DevAppServerMain.run(DevAppServerMain.java:257)
    at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:248)