错误：has been compiled by a more recent version of the Java Runtime (class file version 56.0)

　　具体错误如下：

java.lang.UnsupportedClassVersionError: com/XXX has been compiled by a more recent version of the Java Runtime (class file version 56.0), this version of the Java Runtime only recognizes class file versions up to 52.0 (unable to load class com.XXX)
	org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:3255)

　　意思就是编译时使用了56.0版本，执行时的JDK/JRE使用了52.0版本。两个办法：

• 升级一下JDK。
• 使用运行的JDK重新编译。