eclipse springboot error

❗ 표시 있는 프로젝트

우클릭-Run As-Spring Boot App 실행(Alt+Shift+X,B)

Error Message:

오류: 기본 클래스 com.demo.Demo2Application을(를) 찾거나 로드할 수 없습니다.

원인: project 생성시 Java version이 unbound

해결:

🟢성공 방법1) 새로 project 생성

1. java version 확인
   [cmd] java -version
   
2. project Java Version 동일하게 설정
   [eclipse] New-Other...-Spring Boot-Spring Starter Project-Java Version 선택
   1.8==8
   

🔴실패 방법2) 이미 생성한 project
참고: https://a-magnolia.tistory.com/33
File-properties(Alt+Enter)-Java Build Path-Libraries-Classpath-JRE System Library 더블클릭-Workspace default JRE (jre1.8.0_321) 선택

완료 시 ❗ 표시 사라짐
하지만, 여전히 실행시 오류 메세지

Error: A JNI error has occurred please check your installation and try again

A Java Exception has occurred.

Exception in thread "main" java.lang.UnsupportedClassVersionError: com/demo/Demo2Application has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 52.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(Unknown Source)
	at java.security.SecureClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.access$100(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)