問題描述：
idea進行springboot開發時，進行日誌輸出模式修改，之前沒有對日誌的級別進行設置，啓動的時候也沒有發現有什麼問題。當把日誌級別調整到debug時，啓動springboot項目問題出現了，我當時用的jdk是1.8
Class not found so assuming code is running on a pre-Java 9 JVM
翻譯：
找不到類，所以假設代碼運行在java 9之前的jvm上
完整的異常信息：
2020-06-21 17:44:19.102 DEBUG 5524 --- [ restartedMain] o.apache.tomcat.util.compat.Jre9Compat : Class not found so assuming code is running on a pre-Java 9 JVM
java.lang.ClassNotFoundException: java.lang.reflect.InaccessibleObjectException
at java.net.URLClassLoader.findClass(URLClassLoader.java:382) ~[na:1.8.0_241]
at java.lang.ClassLoader.loadClass(ClassLoader.java:418) ~[na:1.8.0_241]
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:355) ~[na:1.8.0_241]
at java.lang.ClassLoader.loadClass(ClassLoader.java:351) ~[na:1.8.0_241]
at java.lang.Class.forName0(Native Method) ~[na:1.8.0_241]
at java.lang.Class.forName(Class.java:264) ~[na:1.8.0_241]
at org.apache.tomcat.util.compat.Jre9Compat.<clinit>(Jre9Compat.java:81) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.tomcat.util.compat.JreCompat.<clinit>(JreCompat.java:55) [tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.startup.Tomcat.<clinit>(Tomcat.java:1276) [tomcat-embed-core-9.0.36.jar:9.0.36]
at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getWebServer(TomcatServletWebServerFactory.java:177) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:178) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:158) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:545) [spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
at com.lej.gmall.user.GmallUserApplication.main(GmallUserApplication.java:12) [classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_241]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_241]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_241]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_241]
at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.3.1.RELEASE.jar:2.3.1.RELEASE]
解決方法：
jdk更換更高的版本，我當時爲了驗證自己的猜測，在官網上下載了jdk11，然後重新設置項目的jdk，問題沒有再出現，但是又出現了一個其他問題：org.apache.tomcat.jni.LibraryNotFoundError: Can't load library: C:\Users\IdeaProjects\springbootstudy\bin\tcnative-1.dll, Can't load library: 這個問題就是springboot自帶的tomcat中應該沒有tcnative-1.dll，於是纔出現了這個問題，解決方法：從tomcat（tcnative-1.dll這個是分32位或者64位的，根據系統進行下載相關文件) bin目錄中找該文件然後放到自己系統Windows\system32\目錄下，然後重新啓動程序，問題沒再出現。